BIOLOGY 7sem.pdf

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BIOLOGY
Q1. Write the basic difference between science and engineering.
Ans. Science is about knowing and engineering is about doing. Science is
synthesis of knowledge by understanding the law of nature, while
engineering is the application of knowledge to transform the nature for
serving people. Engineers use the scientific knowledge to build processes,
structures and equipment. Both engineers and scientists have sound
knowledge of science, mathematics and technology, but engineers are
trained to use these principles in designing creative solutions to the
challenges. Science is about studying what is existing, engineering is about
creating what never was. Science and engineering both complement each
other, for to transform nature effectively requires proper understanding,
and to discover nature’s secret requires instruments to modify it in
experiments.
The basic difference between science and engineering is that science aims
to answer questions and discover information about how the world works
through observation and experimentation, while engineering aims to
create products or processes that solve problems or improve our lives
through design and innovation. Science follows the scientific method,
where a hypothesis is tested through repeated experiments, while
engineering follows particular approaches to find solutions. Science
expands human perception and understanding, while engineering
expands human plans and results.
Q2. What is the need of study of biology for an engineer?
Ans. The study of biology for an engineer can be useful for several
reasons. Some of them are:
Biology can help engineers understand the structure and function of living
systems, such as plants, animals, and microbes, and how they interact
with their environment.
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Biology can inspire engineers to design and create new products or
processes that mimic or utilize biological systems, such as biomimetic
materials, biotechnology, biomedical engineering, biofuels, etc.
Biology can help engineers solve problems that involve biological systems,
such as environmental engineering, food technology, agricultural
engineering, bioengineering, etc.
Biology can help engineers learn new skills and expand their knowledge in
areas such as genetics, biochemistry, molecular biology, ecology, etc.
Q3. What is biology? Give the characteristics of living organisms?
Ans. Biology is the science of living things that studies their structure,
function, growth, origin, evolution, and distribution. Living things are
those that exhibit certain features that distinguish them from non-living
things. Some of the common characteristics of living organisms are:
 They are made of one or more cells, which are the basic units of life.
 They contain genetic material (DNA or RNA) that carries the
information for their traits and functions.
 They can convert food into energy through metabolic processes
such as cellular respiration or photosynthesis.
 They can grow and develop by increasing their size, number, or
complexity.
 They can reproduce by producing offspring that are similar to
themselves.
 They can respond to stimuli or changes in their environment and
adapt accordingly.
 They can regulate their internal conditions and maintain a stable
state called homeostasis.
 They can move by themselves or with the help of external forces.
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Q4. Differentiate between the basic working mechanism of bird flying
and aircraft flying.
Ans. The basic working mechanism of bird flying and aircraft flying is
based on the same principle of generating lift by moving air over a wing.
However, there are some differences in how birds and airplanes achieve
this:
Birds use their strong breast muscles to flap their wings and give them the
thrust to move through the air and fly. They also use their wings to
control their speed, direction, and altitude by changing the shape, angle,
and orientation of their wings. Airplanes have fixed wings that do not flap,
but instead use engines to thrust them into the air and create the lift
needed to fly. They also use other parts such as flaps, ailerons, rudder,
and elevator to control their flight.
Birds have lightweight, smooth feathers that reduce the forces of weight
and drag4. They also have a beak instead of heavy jaws and teeth, an
enlarged breastbone for flight muscle attachment, and light bones that
are hollow with air sacs. These features help them to fly more efficiently
and maneuverably. Airplanes have a rigid skeleton made of metal or
composite materials that provide strength and durability. They also have
a streamlined body that reduces drag. These features help them to fly
faster and longer.
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Q5. What is the working principle of human eye and digital camera?
Ans. The human eye and the digital camera have some similarities in their
working principle. They both have lenses and light-sensitive surfaces that
capture images of the surrounding environment. However, they also have
some differences in their structure and function.
The human eye operates similar to a digital camera in several ways:
Light focuses mainly on the cornea, which acts like a camera lens.
The iris controls the light that reaches the eye by adjusting the size of the
pupil, and thus it functions like the diaphragm of a camera.
The lens of the eye is located behind the pupil, and it focuses light onto
the retina, which is a light-sensitive surface at the back of the eye. The
retina is made up of millions of nerve cells that convert light into electrical
signals and send them to the brain via the optic nerve.
The digital camera also has some components that are analogous to the
human eye:
The camera lens focuses light onto a sensor, which is a light-sensitive
surface that records the image. The sensor can be either a film or an array
of photoelectric cells in digital cameras.
The aperture is an opening in the lens that controls how much light enters
the camera. It can be adjusted manually or automatically depending on
the lighting conditions.
The shutter is a mechanism that opens and closes to expose the sensor to
light for a certain amount of time. The shutter speed determines how
long the sensor is exposed to light and affects the brightness and motion
blur of the image.
Some differences between the human eye and the digital camera are:
The human eye has a curved retina that can capture a wide field of view,
while the camera sensor is flat and has a limited angle of view.
The human eye can adjust its focus automatically by changing the shape
of the lens, while the camera lens needs a miniature motor to move it
forward and backward to get objects in focus.
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The human eye can adapt to different levels of brightness by changing the
size of the pupil, while the camera needs to adjust both the aperture and
the shutter speed to achieve proper exposure.
The human eye can perceive colors by using three types of cells (rods and
cones) that respond to different wavelengths of light, while the camera
sensor uses filters (red, green and blue) to capture color information.
Q6. Define Mendel’s laws.
Mendel’s laws are a set of three principles that explain the biological
inheritance or heredity of traits. They were proposed by Gregor Mendel,
an Austrian monk and scientist, who conducted experiments on pea
plants in the mid-1860s. The three laws are:
The law of segregation: This law states that every individual organism
contains two alleles (alternative forms) for each trait, and that these
alleles separate during the formation of gametes (sex cells) such that each
gamete contains only one allele for each trait. For example, if an
individual has two alleles for flower color, one purple (P) and one white
(p), then each gamete will receive either P or p randomly.
The law of independent assortment: This law states that the alleles of
different traits are distributed to the gametes independently of each
other, as long as they are located on different chromosomes. For
example, if an individual has two alleles for flower color (P and p) and two
alleles for seed shape (R and r), then the gametes can have any
combination of these alleles, such as PR, Pr, pR or pr.
The law of dominance: This law states that some alleles are dominant
over others, meaning that they mask or hide the expression of the
recessive alleles in the presence of the dominant ones. For example, if an
individual has one allele for purple flower color (P) and one allele for
white flower color (p), then the dominant allele P will determine the
phenotype (appearance) of the individual, which will be purple. The
recessive allele p will not be expressed unless both alleles are p.
Q7. Write Mendel’s law of independent assortment.
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Ans. Mendel’s law of independent assortment can be defined as follows:
The law of independent assortment states that the alleles of two (or
more) different genes get sorted into gametes independently of one
another. In other words, the allele a gamete receives for one gene does
not influence the allele received for another gene.
For example, if an individual has two alleles for flower color (P and p) and
two alleles for seed shape (R and r), then the gametes can have any
combination of these alleles, such as PR, Pr, pR or pr. This means that the
traits of flower color and seed shape are inherited independently of each
other.
Q8. Discuss about the concept of epistasis.
Ans. Epistasis is a concept that describes the interaction between genes
that influences a phenotype1. Epistasis occurs when the expression of
one gene depends on the presence or absence of one or more modifier
genes2. Epistasis can either mask or reveal the effects of other genes,
resulting in different phenotypic ratios than expected from Mendelian
inheritance.
There are different types of epistasis, depending on how the genes
interact with each other. Some common types are:
Dominant epistasis: This occurs when a dominant allele at one locus
masks the expression of both dominant and recessive alleles at another
locus. For example, in summer squash, the color of the fruit is determined
by two genes: W and Y. The dominant allele W produces white color,
while the recessive allele w allows the expression of the Y gene. The
dominant allele Y produces yellow color, while the recessive allele y
produces green color. However, if an individual has at least one W allele,
it will be white regardless of the Y gene. This is an example of dominant
epistasis, where W is epistatic to Y.
Recessive epistasis: This occurs when a recessive allele at one locus masks
the expression of both dominant and recessive alleles at another locus.
For example, in Labrador retrievers, the coat color is determined by two

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genes: B and E. The dominant allele B produces black pigment, while the
recessive allele b produces brown pigment. The dominant allele E allows
the expression of the B gene, while the recessive allele e prevents the
expression of the B gene and produces yellow pigment. However, if an
individual has two e alleles, it will be yellow regardless of the B gene. This
is an example of recessive epistasis, where e is epistatic to B.
Dominant inhibitory epistasis: This occurs when a dominant allele at one
locus suppresses the expression of another gene. For example, in
snapdragons, the flower color is determined by two genes: C and R. The
dominant allele C produces color, while the recessive allele c produces no
color (white). The dominant allele R produces red pigment, while the
recessive allele r produces no pigment (white). However, if an individual
has at least one C allele and at least one R allele, it will produce no color
(white) because C inhibits R. This is an example of dominant inhibitory
epistasis, where C is a suppressor of R.
Duplicate dominant epistasis: This occurs when a dominant allele at either
of two loci can produce the same phenotype. For example, in shepherd’s
purse, the shape of the seed capsule is determined by two genes: A and B.
The dominant alleles A and B produce triangular capsules, while the
recessive alleles a and b produce oval capsules. However, if an individual
has at least one A allele or at least one B allele, it will produce triangular
capsules because either A or B can produce the same phenotype. This is
an example of duplicate dominant epistasis, where A and B are duplicates
of each other.
Duplicate recessive epistasis: This occurs when a recessive allele at either
of two loci can produce the same phenotype. For example, in albinism,
the lack of pigmentation is determined by two genes: O and P. The
dominant alleles O and P produce normal pigmentation, while the
recessive alleles o and p produce no pigmentation (albino). However, if an
individual has two o alleles or two p alleles, it will produce no
pigmentation because either o or p can produce the same phenotype.
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This is an example of duplicate recessive epistasis, where o and p are
complements of each other.
Polymeric gene interaction: This occurs when two or more genes interact
to produce a phenotype that is different from or more extreme than the
sum of their individual effects. For example, in wheat grain color, there
are three genes: A1, A2 and R. The dominant alleles A1 and A2 produce
red pigment, while the recessive alleles a1 and a2 produce no pigment
(white). The dominant allele R enhances the red pigment, while the
recessive allele r reduces it. However, if an individual has both A1 and A2
alleles (A1A2), it will produce purple pigment because A1 and A2 interact
to produce a new color. This is an example of polymeric gene interaction,
where A1 and A2 are polymeric to each other.
Q9. Deliberate about the gene interaction.
Ans. Gene interaction is a phenomenon whereby a single character is
controlled by two or more genes and each gene affects the expression of
the other genes involved1. Gene interaction can result in different
phenotypic ratios than expected from Mendelian inheritance, depending
on how the genes interact with each other.
There are two main types of gene interaction: allelic and non-allelic1.
Allelic gene interaction occurs between the alleles of a single gene, such
as incomplete dominance, codominance, multiple alleles, and lethal
alleles. Non-allelic gene interaction occurs between the genes on
different loci, such as epistasis, complementary genes, duplicate genes,
polygenic inheritance, and pleiotropy.
Epistasis is a type of non-allelic gene interaction where one gene masks or
modifies the expression of another gene2. Epistasis can be classified into
different types based on the mode of inheritance and the phenotypic
ratio produced. Some common types of epistasis are dominant epistasis,
recessive epistasis, dominant inhibitory epistasis, duplicate dominant
epistasis, duplicate recessive epistasis, and polymeric gene interaction.
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Gene interaction is important for understanding the genetic basis of
complex traits and diseases, as well as the evolutionary dynamics of
genetic systems3. Gene interaction can reveal the functional relationships
between genes and the structure of genetic pathways. Gene interaction
can also affect the adaptation and speciation of organisms by creating
novel phenotypes and modifying the effects of natural selection.
Q10. What is genetic code? Write the properties of genetic code.
Ans. Genetic code is the set of rules by which information encoded in
DNA or RNA sequences is translated into proteins by living cells. Genetic
code consists of 64 codons, which are sequences of three nucleotides that
specify a particular amino acid or a stop signal. The genetic code is almost
universal among all living organisms, with some minor exceptions.
Some of the properties of genetic code are:
Triplet: Each codon is composed of three nucleotides, which means that
there are 4^3 = 64 possible combinations of bases. For example, AUG is a
codon that codes for the amino acid methionine.
Non-overlapping: The codons are read sequentially from the 5’ end to the
3’ end of the mRNA molecule, without any gaps or overlaps between
them. For example, if the mRNA sequence is AUGCCAUCU, then the
codons are AUG-CCA-UCU and not AUG-GCC-CAA-UCU.
Commaless: There are no punctuation marks or spacers between the
codons in the mRNA molecule. The codons are adjacent to each other and
form a continuous sequence. For example, if the mRNA sequence is
AUGCCAUCU, then there are no commas or spaces between the codons.
Degenerate: There are more codons than amino acids, which means that
some amino acids are coded by more than one codon. For example, there
are six codons that code for the amino acid leucine: UUA, UUG, CUU, CUC,
CUA and CUG. This property of genetic code provides some redundancy
and protection against mutations.
Unambiguous: Each codon codes for only one amino acid or a stop signal,
which means that there is no ambiguity or confusion in the translation
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process. For example, the codon AUG always codes for methionine and
never for any other amino acid or a stop signal.
Ordered: The codons are arranged in a specific order that reflects the
chemical properties and evolutionary relationships of the amino acids. For
example, the codons that code for amino acids with similar characteristics
tend to have similar first and second bases. Also, the codons that code for
amino acids that are more ancient and common tend to have simpler and
more frequent bases.
Start and stop codons: There are special codons that signal the initiation
and termination of translation. The start codon is usually AUG, which
codes for methionine and marks the beginning of a protein. The stop
codons are UAA, UAG and UGA, which do not code for any amino acid and
mark the end of a protein.
Universal: The genetic code is almost identical among all living organisms,
from bacteria to humans, with some minor variations. This implies that all
living beings share a common ancestry and use a similar language to make
proteins. Some examples of exceptions to the universal genetic code are
mitochondrial DNA, some prokaryotes and some eukaryotes.
Q11. How can you say that DNA is a genetic material?
Ans. DNA is a genetic material because it carries the information for the
synthesis of proteins and the inheritance of traits in living organisms1.
There are several lines of evidence that support DNA as the genetic
material, such as:
Transformation experiments: In 1928, Frederick Griffith discovered that a
non-virulent strain of bacteria could be transformed into a virulent strain
by taking up DNA from a heat-killed virulent strain2. In 1944, Oswald
Avery and his colleagues showed that the transforming agent was DNA
and not protein or RNA3. They used enzymes to degrade different
components of the heat-killed bacteria and found that only DNA-
degrading enzyme prevented transformation.
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Bacteriophage experiments: In 1952, Alfred Hershey and Martha Chase
used radioactive isotopes to label DNA and protein of bacteriophages,
which are viruses that infect bacteria4. They infected bacterial cells with
the labeled phages and separated the phage coats from the bacterial cells
by centrifugation. They found that most of the radioactive DNA entered
the bacterial cells, while most of the radioactive protein remained in the
phage coats. This indicated that DNA was the genetic material that was
transferred from the phages to the bacteria.
Chemical analysis: In 1949, Erwin Chargaff analyzed the composition of
DNA from different sources and found that the amount of adenine (A)
was equal to the amount of thymine (T), and the amount of guanine (G)
was equal to the amount of cytosine © in any given DNA molecule. This
suggested that A paired with T and G paired with C in DNA. In 1953, James
Watson and Francis Crick proposed a double helix model of DNA structure
based on Chargaff’s rules and X-ray diffraction data obtained by Rosalind
Franklin and Maurice Wilkins. The double helix model explained how DNA
could store information in the sequence of bases and how it could
replicate by separating the two strands and using each strand as a
template for a new strand.
Q12. Differentiate between exothermic and endothermic reaction.
Ans. Exothermic and endothermic reactions are two types of chemical
reactions that involve the transfer of heat energy between the system
and the surroundings. The main difference between them is:
Exothermic reactions are chemical reactions that release heat energy to
the surroundings. The products of an exothermic reaction have lower
enthalpy (heat content) than the reactants, and the enthalpy change (ΔH)
is negative. Exothermic reactions usually feel hot because they increase
the temperature of the surroundings. Examples of exothermic reactions
include combustion, neutralization, and respiration.
Endothermic reactions are chemical reactions that absorb heat energy
from the surroundings. The products of an endothermic reaction have
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higher enthalpy than the reactants, and the enthalpy change is positive.
Endothermic reactions usually feel cold because they decrease the
temperature of the surroundings. Examples of endothermic reactions
include photosynthesis, evaporation, and melting.
A table summarizing the differences between exothermic and
endothermic reactions is given below:
Exothermic Reactions Endothermic Reactions
Release heat energy to the
surroundings.
Absorb heat energy from the
surroundings.
Products have lower enthalpy than
reactants.
Products have higher enthalpy
than reactants.
Enthalpy change is negative (ΔH < 0) Enthalpy change is positive (ΔH >
0)
Increase the temperature of the
surroundings.
Decrease the temperature of the
surroundings.
Feel hot Feel cold
Examples: combustion,
neutralization, respiration.
Examples: photosynthesis,
evaporation, melting.
Q13. Classify about types of proteins.
Ans. Proteins are complex organic molecules that are composed of amino
acids linked by peptide bonds. Proteins perform various functions in living
organisms, such as catalyzing biochemical reactions, transporting
molecules, regulating gene expression, providing structural support, and
responding to stimuli.
There are different ways to classify proteins based on their structure,
function, composition, or solubility. Some of the common types of
proteins are:
 Enzymes: These are proteins that act as biological catalysts, meaning
that they speed up the rate of chemical reactions without being
consumed or altered themselves. Enzymes lower the activation
energy required for a reaction to occur and increase the specificity

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and efficiency of the reaction. Enzymes are named according to the
type of reaction they catalyze or the substrate they act on. For
example, amylase is an enzyme that breaks down starch (amylose)
into glucose molecules.
 Structural proteins: These are proteins that provide mechanical
support and shape to cells, tissues, and organs. Structural proteins
are often fibrous, meaning that they have long and thin structures
that are insoluble in water. Some examples of structural proteins are
collagen, which is the main component of connective tissue; keratin,
which is found in hair, nails, and skin; and actin and myosin, which
are involved in muscle contraction and movement.
 Transport proteins: These are proteins that bind and carry molecules
across membranes or in the blood. Transport proteins are often
globular, meaning that they have compact and spherical structures
that are soluble in water. Some examples of transport proteins are
hemoglobin, which carries oxygen in red blood cells; transferrin,
which transports iron in the blood; and aquaporins, which facilitate
the movement of water across cell membranes.
 Regulatory proteins: These are proteins that control or regulate the
activity of other molecules, such as genes, enzymes, or hormones.
Regulatory proteins can act as activators or inhibitors of their target
molecules by binding to them or modifying them. Some examples of
regulatory proteins are transcription factors, which bind to DNA and
regulate gene expression; kinases and phosphatases, which add or
remove phosphate groups from other proteins; and receptors, which
bind to specific ligands (such as hormones or neurotransmitters) and
trigger a cellular response.
 Hormones: These are proteins that act as chemical messengers
between cells, tissues, or organs. Hormones are secreted by
endocrine glands into the bloodstream and travel to their target
cells, where they bind to specific receptors and elicit a physiological
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response. Some examples of protein hormones are insulin, which
regulates blood glucose levels; growth hormone, which stimulates
growth and development; and prolactin, which stimulates milk
production in mammals.
Q14. How can you say that proteins act as structural elements of a living
cell?
Ans. Proteins act as structural elements of a living cell because they
provide mechanical support and shape to the cell and its
components. Proteins are the main constituents of the cell membrane,
the cytoskeleton, the cell wall (in plants, fungi, and bacteria), and the
extracellular matrix. Proteins also form the basis of many cellular
organelles, such as ribosomes, mitochondria, chloroplasts, and cilia.
Structural proteins confer stiffness and rigidity to otherwise-fluid
biological components. Most structural proteins are fibrous protein; for
example, collagen and elastin are critical components of connective tissue
such as cartilage, and keratin is found in hard or filamentous structures
such as hair, nails, feathers, hooves, and some animal shells
Some globular proteins can also play structural functions, for
example, actinand tubulin are globular and soluble as monomers,
but polymerizeto form long, stiff fibers that make up the cytoskeleton,
which allows the cell to maintain its shape and size.
Other proteins that serve structural functions are motor proteins such
as myosin, kinesin, and dynein, which are capable of generating
mechanical forces. These proteins are crucial for cellular motility of single
celled organisms and the sperm of many multicellular organisms which
reproduce sexually. They also generate the forces exerted by
contracting muscles and play essential roles in intracellular transport.
Q15. How can you say that proteins are transporters and receptors of a
living cell?
Ans. Proteins are transporters and receptors of a living cell because they
facilitate the movement and recognition of molecules across the cell
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membrane and within the cell. Proteins are involved in both passive and
active transport mechanisms that allow molecules to cross the membrane
along or against their concentration gradients. Proteins also act as
receptors that bind to specific ligands (such as hormones,
neurotransmitters, or growth factors) and trigger a cellular response.
Some examples of proteins that act as transporters and receptors of a
living cell are:
 Glucose transporter: This is a transmembrane protein that transports
glucose across the cell membrane by facilitated diffusion, a passive
transport mechanism that does not require energy. Glucose
transporter allows glucose to enter the cell when its concentration is
higher outside than inside, and to exit the cell when its concentration
is higher inside than outside.
 Sodium-potassium pump: This is a transmembrane protein that
transports sodium and potassium ions across the cell membrane by
active transport, a transport mechanism that requires energy in the
form of ATP. Sodium-potassium pump pumps three sodium ions out
of the cell and two potassium ions into the cell for each ATP
molecule consumed, creating an electrochemical gradient that is
essential for nerve impulses, muscle contraction, and osmotic
balance.
 Insulin receptor: This is a transmembrane protein that binds to
insulin, a hormone that regulates blood glucose levels. Insulin
receptor activates a signaling pathway that stimulates the uptake of
glucose by cells and the synthesis of glycogen, a storage form of
glucose.
 G protein-coupled receptor: This is a transmembrane protein that
binds to various ligands, such as hormones, neurotransmitters, or
sensory stimuli. G protein-coupled receptor activates a G protein,
which in turn activates an enzyme or an ion channel that produces a
second messenger, such as cyclic AMP or calcium. The second
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messenger then modulates the activity of other proteins, such as
kinases or transcription factors, leading to various cellular responses.
Q16. Differentiate between autotroph and heterotroph organisms.
Ans. Autotroph and heterotroph organisms are two types of organisms
that differ in their mode of nutrition. The main difference between them
is:
 Autotroph organisms are organisms that can produce their own food
using light or chemical energy from substances available in their
surroundings. They obtain carbon from inorganic sources like carbon
dioxide. Autotrophs are also called “self feeders” or “primary
producers” and are usually plants. Autotrophs are the primary
producers and are placed first in the food chain.
 Heterotroph organisms are organisms that cannot synthesize their
own food and rely on other organisms for nutrition. They include
herbivores, carnivores, omnivores, and decomposers. Heterotrophs
cannot use carbon dioxide as a source of carbon and must obtain
organic molecules from autotrophs or other
heterotrophs. Heterotrophs are also called “other feeders” or
“consumers” and are usually animals. Heterotrophs are the
consumers and are placed at a secondary or tertiary level in the food
chain.
A table summarizing the differences between autotroph and heterotroph
organisms is given below:
Autotroph Organisms Heterotroph Organisms
Can produce their
own food using light
or chemical energy
Cannot produce their own food and depend on
other sources for their food
Obtain carbon from
inorganic sources like
Obtain carbon from organic sources like
carbohydrates, lipids, and proteins
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Autotroph Organisms Heterotroph Organisms
carbon dioxide
Are also called “self
feeders” or “primary
producers” Are also called “other feeders” or “consumers”
Are usually plants Are usually animals
Are placed first in the
food chain
Are placed at a secondary or tertiary level in the
food chain
Q17. What are dominant traits in living organism?
Ans. Dominant traits in living organisms are inherited characteristics that
appear in an offspring if they are contributed from a parent through a
dominant allele. An allele is a version of a gene that codes for a specific
trait. A dominant allele is an allele that masks the effect of another allele
(called a recessive allele) when both are present in an individual. For
example, if a gene has two alleles, A and a, and A is dominant over a, then
an individual with AA or Aa genotype will have the same phenotype
(observable feature) as determined by the A allele. Only an individual with
aa genotype will have the phenotype determined by the a allele.
Some examples of dominant traits in living organisms are:
 Dark hair: Dark hair is dominant over blonde or red hair in humans.
This means that a person with at least one dominant allele for dark
hair (DD or Dd) will have dark hair, while only a person with two
recessive alleles for light hair (dd) will have blonde or red hair.
 Curly hair: Curly hair is dominant over straight hair in humans. This
means that a person with at least one dominant allele for curly hair
(CC or Cc) will have curly hair, while only a person with two recessive
alleles for straight hair (cc) will have straight hair.
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 Baldness: Baldness is a dominant trait in humans, but it is also
influenced by sex chromosomes. This means that a male with at least
one dominant allele for baldness (BB or Bb) will be bald, while only a
male with two recessive alleles for non-baldness (bb) will have hair.
However, a female with one dominant allele for baldness (Bb) will
not be bald, but will be a carrier of the trait. Only a female with two
dominant alleles for baldness (BB) will be bald.
 Widow’s peak: A widow’s peak is a V-shaped hairline that is
dominant over a straight hairline in humans. This means that a
person with at least one dominant allele for widow’s peak (WW or
Ww) will have a widow’s peak, while only a person with two
recessive alleles for straight hairline (ww) will have a straight
hairline.
 Purple flowers: Purple flower color is dominant over white flower
color in pea plants. This means that a pea plant with at least one
dominant allele for purple flowers (PP or Pp) will have purple
flowers, while only a pea plant with two recessive alleles for white
flowers (pp) will have white flowers.
Q18. Write the examples of single-cell organisms and multicellular
organism.
Ans. Single-cell organisms and multicellular organisms are two types of
organisms that differ in the number and organization of their cells. The
main difference between them is:
 Single-cell organisms are organisms that are made up of only one
cell. They are the simplest form of life and can perform all the
necessary functions for their survival within a single cell. Single-cell
organisms include bacteria, protists, and yeast. They are mostly
microscopic and invisible to the naked eye. They can be either
prokaryotes (lacking a nucleus and membrane-bound organelles) or
eukaryotes (having a nucleus and membrane-bound organelles).

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 Multicellular organisms are organisms that are made up of more
than one cell. They have a complex body organization and different
types of cells that are specialized to carry out specific
functions. Multicellular organisms include animals, plants, and
fungi. They are mostly macroscopic and visible to the naked
eye. They are all eukaryotes and have a nucleus and membrane-
bound organelles in each cell.
Some examples of single-cell organisms are:
 Amoeba: This is a protist that lives in freshwater habitats and feeds
on bacteria and other microorganisms. It has an irregular shape and
moves by extending pseudopods (false feet) from its cytoplasm.
 Euglena: This is a protist that lives in freshwater habitats and can be
either autotrophic (making its own food by photosynthesis) or
heterotrophic (obtaining food from the environment). It has a
flagellum (a whip-like structure) that helps it swim and an eyespot (a
light-sensitive organelle) that helps it detect light.
 Paramecium: This is a protist that lives in freshwater habitats and
feeds on bacteria and other microorganisms by sweeping them into
its oral groove with cilia (tiny hair-like structures). It has a slipper-like
shape and two nuclei: a large macronucleus that controls most of the
cell functions and a small micronucleus that is involved in sexual
reproduction.
 Plasmodium: This is a protist that causes malaria, a disease that
affects millions of people worldwide. It has a complex life cycle that
involves two hosts: a mosquito vector and a human host. It infects
the red blood cells of the human host and causes fever, chills,
headache, and other symptoms.
 Nostoc: This is a cyanobacterium that forms filamentous colonies in
freshwater or moist habitats. It can fix nitrogen from the air and
convert it into usable forms for other organisms. It also produces
oxygen as a by-product of photosynthesis.
20
 Salmonella: This is a bacterium that causes food poisoning, typhoid
fever, and other diseases in humans and animals. It is rod-shaped
and has flagella for motility. It invades the intestinal cells of the host
and triggers an inflammatory response that leads to diarrhea,
vomiting, fever, and abdominal pain.
Some examples of multicellular organisms are:
 Humans: These are animals that belong to the class Mammalia and
the order Primates. They have a highly developed brain, bipedal
locomotion, opposable thumbs, and complex language skills. They
have various types of cells, such as nerve cells, skin cells, muscle
cells, blood cells, etc., that form tissues, organs, and organ systems.
 Animals: These are multicellular eukaryotes that belong to the
kingdom Animalia. They are heterotrophic, meaning they obtain food
from other sources rather than making their own food by
photosynthesis. They have various types of cells, such as epithelial
cells, muscle cells, nerve cells, etc., that form tissues, organs, and
organ systems.
 Plants: These are multicellular eukaryotes that belong to the
kingdom Plantae. They are autotrophic, meaning they make their
own food by photosynthesis using light energy from the sun. They
have various types of cells, such as parenchyma cells, collenchyma
cells, sclerenchyma cells, etc., that form tissues, organs, and organ
systems.
 Birds: These are animals that belong to the class Aves and have
feathers, wings, beaks, and hollow bones. They are endothermic,
meaning they maintain a constant body temperature by generating
heat internally. They have various types of cells, such as red blood
cells, white blood cells, epithelial cells, etc., that form tissues, organs,
and organ systems.
 Insects: These are animals that belong to the class Insecta and have
three pairs of legs, three body segments (head, thorax, abdomen),
21
compound eyes, antennae, and usually wings. They are ectothermic,
meaning they rely on external sources of heat to regulate their body
temperature. They have various types of cells, such as nerve cells,
muscle cells, glandular cells, etc., that form tissues, organs, and
organ systems.
Q19. Discuss about how biological discovery in 20th
century led to major
investigation in environmental science.
Ans. Biological discovery in the 20th century led to major investigation in
environmental science because it revealed the diversity, complexity, and
interdependence of life on Earth and the impact of human activities on
the natural environment. Some of the biological discoveries that
influenced environmental science are:
 The discovery of DNA and its role in heredity and evolution: In 1953,
James Watson and Francis Crick proposed the double helix model of
DNA structure based on X-ray diffraction data obtained by Rosalind
Franklin and Maurice Wilkins. They showed that DNA is the molecule
that carries genetic information from one generation to the next and
that it can undergo mutations that result in variation and evolution.
The discovery of DNA opened new fields of study such as molecular
biology, genetics, genomics, and biotechnology. It also enabled
scientists to explore the diversity of life at the molecular level, to
trace the evolutionary relationships among different organisms, and
to manipulate genes for various purposes. The discovery of DNA also
raised ethical and social issues regarding the use and misuse of
genetic information and technology.
 The development of ecology and the concept of ecosystems: Ecology
is the branch of biology that studies the interactions of organisms
with each other and with their physical environment. Ecology
emerged as a distinct discipline in the early 20th century, influenced
by the work of scientists such as Ernst Haeckel, who coined the term
ecology in 1866; Arthur Tansley, who introduced the concept of
22
ecosystem in 1935; and Eugene Odum, who popularized the study of
ecosystems in the 1950s. Ecology provided a holistic perspective on
the complex and dynamic relationships among living and nonliving
components of nature. It also helped to identify and address
environmental problems such as pollution, habitat loss, biodiversity
loss, climate change, and invasive species.
 The discovery of antibiotics and their role in medicine and
agriculture: Antibiotics are substances that can kill or inhibit the
growth of bacteria and other microorganisms. The discovery of
antibiotics revolutionized medicine and agriculture in the 20th
century by providing effective treatments for many infectious
diseases and enhancing crop and animal production. The first
antibiotic to be discovered was penicillin, which was isolated from a
mold by Alexander Fleming in 1928. Other antibiotics were later
discovered from natural sources or synthesized in laboratories.
However, the widespread use of antibiotics also led to the
emergence of antibiotic-resistant bacteria, which pose a serious
threat to human health and food security. The discovery of
antibiotics also stimulated research on microbiology, immunology,
pharmacology, and biotechnology.
 The exploration of biodiversity and its importance for ecosystem
functioning and human well-being: Biodiversity is the variety of life
on Earth at all levels of organization, from genes to species to
ecosystems. Biodiversity is essential for maintaining ecosystem
functioning and providing ecosystem services that support human
well-being. The exploration of biodiversity in the 20th century was
facilitated by advances in taxonomy, biogeography, phylogenetics,
molecular biology, ecology, conservation biology, and biotechnology.
Scientists discovered new species and new aspects of known species
in various habitats across the globe. They also documented the
patterns and processes of biodiversity distribution, evolution,
23
adaptation, and extinction. They also assessed the threats and
challenges facing biodiversity conservation and sustainable use.
Q20. Define the term of primary structure of protein.
Ans. The primary structure of protein is the sequence of amino acids that
are linked together by peptide bonds to form a polypeptide chain. The
primary structure of protein determines its identity and function, as any
change in the amino acid sequence can alter the shape and properties of
the protein. The primary structure of protein is written from the N-
terminus (the end with a free amino group) to the C-terminus (the end
with a free carboxyl group) using either the three-letter or one-letter
symbols of amino acids. For example, the primary structure of insulin A
chain is:
Gly-Ile-Val-Glu-Gln-Cys-Cys-Thr-Ser-Ile-Cys-Ser-Leu-Tyr-Gln-Leu-Glu-Asn-
Tyr-Cys-Asn
or
GIVEQCCTSICSLYQLENYCN
The primary structure of protein can be visualized as a linear string of
beads, where each bead represents an amino acid. The following picture
shows an example of the primary structure of a protein:
Q21. Differentiate between photosynthesis and respiration in plant.
24
Ans. Photosynthesis and respiration in plants are two processes that
involve the exchange of gases and the production and consumption of
energy. The main difference between them is:
 Photosynthesis is the process in which green plants use light energy
from the sun to convert carbon dioxide and water into glucose and
oxygen. Photosynthesis occurs in the chloroplasts of plant cells,
which contain the green pigment chlorophyll that absorbs light.
Photosynthesis can be summarized by the following equation:
6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Photosynthesis produces glucose, which is used as food by the plant and
stored as starch or cellulose. Photosynthesis also produces oxygen, which
is released into the atmosphere and used by other organisms for
respiration.
 Respiration is the process in which all living organisms, including
plants, break down glucose and oxygen to produce carbon dioxide,
water, and energy. Respiration occurs in the mitochondria of cells,
which are the sites of cellular energy production. Respiration can be
summarized by the following equation:
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Respiration consumes glucose and oxygen, which are obtained from
photosynthesis or from other sources. Respiration produces carbon
dioxide and water, which are released as waste products or used for other
purposes. Respiration also produces energy in the form of ATP (adenosine
triphosphate), which is used to power various cellular activities1
.
A table summarizing the differences between photosynthesis and
respiration in plants is given below:
Photosynthesis Respiration
Occurs in chloroplasts Occurs in mitochondria
Uses light energy Uses chemical energy

5. 25
Photosynthesis Respiration
Converts carbon dioxide
and water into glucose
and oxygen
Converts glucose and
oxygen into carbon
dioxide and water
Produces food and oxygen
Produces energy and
waste
Q22. Differentiate between photosynthesis and transpiration in plant.
Ans. Photosynthesis and transpiration in plants are two processes that
involve the movement of water and gases in and out of the plant. The
main difference between them is:
 Photosynthesis is the process in which green plants use light energy
from the sun to convert carbon dioxide and water into glucose and
oxygen. Photosynthesis occurs in the chloroplasts of plant cells,
which contain the green pigment chlorophyll that absorbs light.
Photosynthesis can be summarized by the following equation:
6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Photosynthesis produces glucose, which is used as food by the plant and
stored as starch or cellulose. Photosynthesis also produces oxygen, which
is released into the atmosphere and used by other organisms for
respiration.
 Transpiration is the process in which water is lost from the plant as
water vapor through the stomata (small pores) on the surface of the
leaves. Transpiration occurs as a result of evaporation of water from
the mesophyll cells (cells that contain chloroplasts) and diffusion of
water vapor into the air spaces within the leaf and then out of the
stomata. Transpiration can be summarized by the following
equation:
H2O → H2O (vapor)
26
Transpiration consumes water, which is absorbed by the roots from the
soil and transported through the xylem (water-conducting tissue) to the
leaves. Transpiration has several functions, such as cooling the plant,
creating a negative pressure that pulls water up the xylem, and facilitating
the uptake of mineral ions from the soil.
A table summarizing the differences between photosynthesis and
transpiration in plants is given below:
Photosynthesis Transpiration
Occurs in chloroplasts Occurs in stomata
Uses light energy Uses heat energy
Converts carbon dioxide and
water into glucose and
oxygen
Converts water into
water vapor
Produces food and oxygen
Consumes water and
cools the plant
Q23. Differentiate between prokaryote and eukaryote organisms.
Ans. Prokaryote and eukaryote organisms are two groups of living
organisms that differ in the structure and complexity of their cells. The
main difference between them is:
 Prokaryote organisms are organisms that are made up of cells that
lack a nucleus or any membrane-bound organelles. This means that
their genetic material (DNA) is not enclosed in a nuclear envelope,
but is free-floating in the cytoplasm. Prokaryote cells are also simpler
and smaller than eukaryote cells, and have a circular DNA molecule
called a plasmid that can replicate independently of the main
chromosome. Prokaryote organisms include bacteria and archaea,
27
which are mostly unicellular and can live in diverse and extreme
environments1
.
 Eukaryote organisms are organisms that are made up of cells that
have a nucleus and membrane-bound organelles. This means that
their genetic material (DNA) is organized into linear chromosomes
and is separated from the cytoplasm by a nuclear envelope.
Eukaryote cells are also more complex and larger than prokaryote
cells, and have various organelles such as mitochondria, chloroplasts,
endoplasmic reticulum, Golgi apparatus, lysosomes, etc. that
perform specialized functions. Eukaryote organisms include plants,
animals, fungi, and protists, which can be either unicellular or
multicellular and have diverse forms and functions.
A table summarizing the differences between prokaryote and eukaryote
organisms is given below:
Prokaryote Organisms Eukaryote Organisms
Made up of cells without a
nucleus or membrane-bound
organelles
Made up of cells with a nucleus
and membrane-bound organelles
Have free-floating circular DNA
and plasmids
Have linear chromosomes
enclosed in a nuclear envelope
Simpler and smaller cells More complex and larger cells
Include bacteria and archaea
Include plants, animals, fungi,
and protists
Mostly unicellular and
extremophilic
Can be either unicellular or
multicellular and diverse
28
Q24. Briefly describe the mechanism of protein synthesis in eukaryotic
cell.
Ans. Protein synthesis in eukaryotic cell is the process of translating the
sequence of a messenger RNA (mRNA) molecule to a sequence of amino
acids during protein synthesis. It involves two main steps: transcription
and translation.
Transcription is the transfer of genetic information from DNA to mRNA in
the nucleus. During transcription, a strand of mRNA is made that is
complementary to a strand of DNA called a gene. A gene contains a
promoter, a coding sequence, and a terminator. The promoter is where
RNA polymerase attaches and starts transcription. The coding sequence is
the part of the gene that encodes the protein. The terminator is where
transcription ends. After transcription, the mRNA undergoes processing,
such as splicing, capping, and polyadenylation.
Translation is the synthesis of protein from mRNA at the ribosome in the
cytoplasm or on the endoplasmic reticulum. During translation, the
ribosome reads the nucleotide sequence of the mRNA from 5’ to 3’
direction and synthesizes the corresponding protein from amino acids in
an N-terminal to C-terminal direction. Translation requires several factors,
such as initiation factors, elongation factors, and termination factors. The
initiating amino acid in eukaryotes is methionine. Translation ends when a
stop codon is reached on the mRNA.
Q25. If you could not have a microscope, how would you determine
whether a cell is prokaryotic or eukaryotic? Suppose that the organisms
can be easily found in the laboratory.
Ans. If I could not have a microscope, I would try to determine whether a
cell is prokaryotic or eukaryotic based on some of the following criteria:
 Size: Prokaryotic cells are much smaller than eukaryotic cells, usually
ranging from 0.1 to 5 micrometers in diameter, while eukaryotic cells
are typically 10 to 100 micrometers in diameter. Therefore, I could
try to measure the size of the cell using a ruler or a magnifying glass
29
and compare it with the average size of prokaryotic and eukaryotic
cells.
 Shape: Prokaryotic cells have three basic shapes: cocci (spherical),
bacilli (rod-shaped), and spirilla (spiral-shaped). Eukaryotic cells have
more diverse and complex shapes, such as star-shaped, oval-shaped,
or branched2
. Therefore, I could try to observe the shape of the cell
and see if it matches any of the common prokaryotic shapes or not.
 Organization: Prokaryotic cells are always unicellular, meaning they
exist as single cells. Eukaryotic cells can be either unicellular or
multicellular, meaning they can form colonies, tissues, organs, or
organisms. Therefore, I could try to see if the cell is isolated or part
of a larger structure and infer its cellular organization.
 Organelles: Prokaryotic cells lack membrane-bound organelles, such
as a nucleus, mitochondria, chloroplasts, or endoplasmic
reticulum. Eukaryotic cells have these organelles and more, which
perform various functions within the cell. Therefore, I could try to
stain the cell with different dyes and see if any organelles are visible
under a magnifying glass or a simple lens.
These are some of the possible ways to determine whether a cell is
prokaryotic or eukaryotic without a microscope. However, these methods
are not very accurate or reliable and may not work for all types of cells.
Therefore, using a microscope is the best way to identify the type of cell
based on its structure and features.
Q26. Explain the laws of thermodynamics especially with relation to
biological systems.
Ans. The laws of thermodynamics are physical principles that describe
how energy is transferred and transformed in natural systems. They apply
to biological systems as well as physical systems, such as engines or
chemical reactions. There are four laws of thermodynamics, but the first
two are the most relevant for biology.
30
The first law of thermodynamics states that energy can neither be created
nor destroyed, but only converted from one form to another. This means
that the total amount of energy in a closed system (such as the universe)
remains constant. However, in an open system (such as a living organism),
energy can be exchanged with the surroundings. For example, plants
absorb light energy from the sun and convert it into chemical energy
stored in glucose molecules. Animals consume plants or other animals
and use the chemical energy to perform work, such as movement,
growth, or reproduction. Some of the energy is also lost as heat to the
environment.
The second law of thermodynamics states that the entropy (disorder) of a
closed system always increases over time. This means that energy tends
to become more dispersed and less useful for doing work. For example,
when a hot object cools down, it transfers heat energy to its
surroundings, increasing their entropy. Similarly, when a chemical
reaction occurs, it releases some energy as heat, increasing the entropy of
the system and the surroundings. In biological systems, entropy also
increases as molecules break down into simpler forms or as cells die and
decompose.
However, biological systems can also maintain or decrease their entropy
by using energy from their surroundings. For example, plants use light
energy to synthesize complex organic molecules from simple inorganic
molecules, decreasing their entropy. Animals use chemical energy to build
and maintain their structures and functions, decreasing their entropy.
These processes require constant input of energy and matter from the
environment, which increases its entropy. Therefore, biological systems
can only temporarily decrease their entropy at the expense of increasing
the entropy of their surroundings.
These are the main laws of thermodynamics and how they relate to
biological systems. They explain how energy flows and changes in living
organisms and their interactions with the environment.

6. 31
Q27. Draw the flow chart of Krebs cycle.
Q28. Draw a flowchart of photosynthesis cycle in reference to synthesis
of glucose in plant.
32
Q29. What are the characteristics features of prokaryotic cells?
Ans. Prokaryotic cells are the cells that do not have a true nucleus and
membrane-bound organelles. They are usually single-celled organisms
belonging to the domains Bacteria and Archaea. Some of the
characteristic features of prokaryotic cells are:
 They have a nucleoid region where the genetic material (DNA and
RNA) is located.
 They have ribosomes that synthesize proteins.
 They have a cell membrane that surrounds the cytoplasm and
regulates the entry and exit of substances.
 They have a cell wall that provides shape and protection to the
cell. The cell wall is made of peptidoglycan in most bacteria and of
other materials in archaea.
33
 Some of them have a capsule or a slime layer that covers the cell wall
and helps in moisture retention, attachment, and protection.
 Some of them have flagella, pili, or fimbriae that are used for
locomotion, genetic exchange, or attachment respectively.
Q30. What is cell theory?
Ans. Cell theory is a scientific theory that states that all living organisms
are composed of cells, that they are the basic structural/organizational
unit of all organisms, and that all cells come from pre-existing cells. Cell
theory was first formulated in the mid-nineteenth century by German
scientists Theodor Schwann, Matthias Schleiden, and Rudolf Virchow. Cell
theory marked a great conceptual advance in biology and resulted in
renewed attention to the living processes that go on in cells.
Cell theory has many implications and applications for biology and
medicine. For example, it explains how organisms grow, develop, and
reproduce by cell division. It also provides a basis for understanding how
diseases are caused by abnormal or dysfunctional cells. It also allows for
the development of biotechnology and genetic engineering by
manipulating cells and their components.
Q31. Who has given the five kingdom classification?
Ans. The five kingdom classification is a system of categorizing living
organisms into five major groups based on certain characteristics. The five
kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. The five
kingdom classification was given by American biologist Robert Whittaker
in 1969.
The five kingdom classification is based on the following criteria:
 The structure of the cell: whether it is prokaryotic (lacking a true
nucleus and membrane-bound organelles) or eukaryotic (having a
true nucleus and membrane-bound organelles).
 The mode of nutrition: whether it is autotrophic (making its own
food by photosynthesis or chemosynthesis) or heterotrophic
34
(obtaining food from other sources by ingestion, absorption, or
parasitism).
 The source of nutrition: whether it is organic (carbon-containing) or
inorganic (non-carbon-containing).
 The interrelationship: whether it is free-living (independent) or
symbiotic (dependent on another organism).
 The body organization: whether it is unicellular (single-celled) or
multicellular (many-celled).
 The reproduction: whether it is asexual (without fusion of gametes)
or sexual (with fusion of gametes).
The main features and examples of each kingdom are:
 Kingdom Monera: These are prokaryotic, unicellular, and mostly
heterotrophic organisms. They have a cell wall and can be motile or
non-motile. They can be found in various habitats and show a great
diversity of metabolism. Examples are bacteria, cyanobacteria, and
mycoplasma.
 Kingdom Protista: These are eukaryotic, mostly unicellular, and
mostly autotrophic organisms. They have a cell membrane and can
be motile or non-motile. They are mostly aquatic and show a great
diversity of forms and functions. Examples are protozoa, algae, slime
molds, and water molds.
 Kingdom Fungi: These are eukaryotic, mostly multicellular, and
heterotrophic organisms. They have a cell wall made of chitin and
are non-motile. They obtain their nutrition by absorption of organic
matter from dead or living sources. They reproduce by spores and
show a filamentous body structure called mycelium. Examples are
mushrooms, molds, yeasts, and lichens.
 Kingdom Plantae: These are eukaryotic, multicellular, and
autotrophic organisms. They have a cell wall made of cellulose and
are non-motile. They obtain their nutrition by photosynthesis using
chlorophyll. They reproduce by spores or seeds and show a
35
differentiated body structure with roots, stems, leaves, and flowers.
Examples are mosses, ferns, gymnosperms, and angiosperms.
 Kingdom Animalia: These are eukaryotic, multicellular, and
heterotrophic organisms. They have a cell membrane and are motile.
They obtain their nutrition by ingestion of organic matter from other
sources. They reproduce by sexual means and show a high degree of
body organization with tissues, organs, and systems. Examples are
sponges, cnidarians, worms, mollusks, arthropods, echinoderms, and
vertebrates.
Q32. What is the difference between gene and allele?
Ans. The difference between gene and allele can be presented in a
tabular form as follows:
Gene Allele
A gene is a portion of DNA that
codes for a specific protein or
function.
An allele is a variant form of a gene that
may have a different sequence of
nucleotides or a different expression
level.
A gene is responsible for the
expression of a trait.
An allele is responsible for the variation
in which a trait can be expressed.
A gene can have many different
alleles.
An individual has two alleles for each
gene, one inherited from each parent.
A gene does not occur in pairs.
Alleles occur in pairs and can be
homozygous (same) or heterozygous
(different).
Examples of genes are eye color,
hair color, blood type.
Examples of alleles are blue eyes, brown
hair, A blood type.
36
Q33. Explain the concept of linkage?
Ans. The concept of linkage is the tendency of genes or other DNA
sequences that are close together on the same chromosome to be
inherited together during the meiosis phase of sexual
reproduction. Linkage affects the proportions of gametes and the
association of traits that are produced by meiosis, which is the cell
division that produces sperm or egg cells. Linkage can be measured by the
amount of recombination or crossing over between genes, which is the
exchange of genes between chromosomes that occurs during meiosis.
Linkage groups are all the genes on a single chromosome that act and
move as a unit. Sex linkage is a type of linkage that involves genes on the
sex chromosomes.
Linkage is an exception to Mendel’s law of independent assortment,
which states that genes on different chromosomes are inherited
independently. When genes are linked, they do not assort independently
and their alleles tend to be inherited together more often than not. This
results in deviations from the expected ratios of phenotypes and
genotypes in genetic crosses involving linked genes. For example, if two
genes A and B are linked on the same chromosome, and an individual
with genotype AB/ab (where AB and ab are two homologous
chromosomes) produces gametes, most of the gametes will have either
AB or ab combinations, rather than Ab or aB recombinants. The frequency
of recombinants depends on how far apart the genes are on the
chromosome and how often crossing over occurs between them. The
farther apart the genes are, the more likely they are to recombine and
appear to assort independently. The closer they are, the more likely they
are to stay together and appear to be linked.
Linkage can be used to construct genetic maps that show the order and
relative distances of genes on a chromosome. By finding the
recombination frequencies for many pairs of genes, one can estimate how
far apart they are in terms of map units or centimorgans (cM). One map

7. 37
unit or centimorgan is equivalent to a 1% chance of recombination
between two genes. For example, if two genes have a recombination
frequency of 0.05 or 5%, they are 5 cM apart on the chromosome. By
comparing the recombination frequencies of different gene pairs, one can
determine which genes are closer or farther from each other and arrange
them in a linear order. Genetic maps can help identify genes that are
responsible for certain traits or diseases by finding markers that are linked
to them.
Q34. Discuss the different phases of cell cycle?
Ans. The cell cycle is a series of events that take place in a cell, resulting in
the duplication of DNA and division of cytoplasm and organelles to
produce two daughter cells. The cell cycle can be divided into two main
phases: interphase and mitotic phase.
Interphase is the phase in which the cell grows and prepares for division.
It consists of three subphases: G1, S, and G2.
 G1 phase: The cell increases in size and synthesizes proteins and
other molecules needed for cell division.
 S phase: The cell replicates its DNA, resulting in two identical copies
of each chromosome.
 G2 phase: The cell continues to grow and produce proteins and
organelles required for mitosis and cytokinesis.
Mitotic phase is the phase in which the cell divides into two genetically
identical daughter cells. It consists of two processes: mitosis and
cytokinesis.
 Mitosis: The process of nuclear division in which the duplicated
chromosomes are separated and distributed to two daughter nuclei.
Mitosis can be further divided into four stages: prophase,
metaphase, anaphase, and telophase.
o Prophase: The chromosomes condense and become visible. The
nuclear envelope breaks down. The spindle fibers form and
attach to the centromeres of the chromosomes.
38
o Metaphase: The chromosomes align at the equator of the
cell. The spindle fibers exert tension on the chromosomes.
o Anaphase: The sister chromatids separate and move to opposite
poles of the cell. The cell elongates as the spindle fibers pull
apart.
o Telophase: The chromosomes reach the poles and decondense.
The nuclear envelope reforms around each set of
chromosomes. The spindle fibers disassemble.
 Cytokinesis: The process of cytoplasmic division in which the cell
membrane pinches inward and splits the cell into two daughter cells.
In animal cells, a cleavage furrow forms at the equator of the cell. In
plant cells, a cell plate forms at the equator of the cell.
Q35. What is the cell? Differentiate between plant cell and animal cell?
39
Ans. A cell is the basic structural and functional unit of any living
organism. It is the smallest entity that can carry out the processes of life,
such as metabolism, growth, reproduction, and response to stimuli. Cells
can be classified into two types: prokaryotic and eukaryotic. Prokaryotic
cells are simple and lack a nucleus and membrane-bound organelles.
Eukaryotic cells are complex and have a nucleus and membrane-bound
organelles.
Plant cells and animal cells are both examples of eukaryotic cells. They
share some common features, such as a plasma membrane, cytoplasm,
nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus,
mitochondria, and lysosomes. However, they also have some differences
that reflect their different functions and adaptations. The main
differences between plant cells and animal cells are:
Plant cell Animal cell
Plant cells have a cell wall that surrounds
the plasma membrane and provides shape
and rigidity to the cell.
Animal cells do not have a
cell wall.
Plant cells have chloroplasts that contain
chlorophyll and help in photosynthesis,
which is the process of converting light
energy into chemical energy.
Animal cells do not have
chloroplasts.
Plant cells have a large central vacuole that
occupies most of the cell volume and stores
water, ions, sugars, and other substances.
animal cells have smaller
and more numerous
vacuoles that store various
materials.
Plant cells are mostly regular in shape and
rectangular in size.
Animal cells are irregular in
shape and vary in size.
40
Plant cell Animal cell
Animal cells have centrioles that are
involved in organizing the spindle fibers
during cell division.
plant cells do not have
centrioles.
Q36. Explain all the stages of meiosis with well labeled diagram?
Ans. Meiosis is a type of cell division that produces four haploid daughter
cells from a single diploid parent cell. Meiosis is essential for sexual
reproduction, as it ensures the transmission of genetic variation and the
maintenance of the chromosome number in each generation.
Meiosis involves two successive stages or phases of cell division, meiosis I
and meiosis II. Each stage includes a period of nuclear division or
karyokinesis and a cytoplasmic division or cytokinesis. Although not a part
of meiosis, the cells before entering meiosis I undergo a compulsory
growth period called interphase, during which they replicate their DNA
and prepare for cell division.
The stages of meiosis with well labeled diagrams are as follows:
 Meiosis I: This is the reductional division, in which the chromosome
number is halved from diploid (2n) to haploid (n). Meiosis I consists
of four sub-stages: prophase I, metaphase I, anaphase I, and
telophase I.
o Prophase I: This is the longest and most complex stage of
meiosis, which can be further divided into five phases:
leptotene, zygotene, pachytene, diplotene, and diakinesis.
 Leptotene: The chromosomes start to condense and
become visible as thin threads. The nuclear envelope and
nucleolus are still intact.
 Zygotene: The homologous chromosomes (one from each
parent) pair up along their length and form bivalents or
41
tetrads. This process is called synapsis. The points of
contact between the homologous chromosomes are called
chiasmata.
 Pachytene: The paired chromosomes become shorter and
thicker. The exchange of genetic material between the
non-sister chromatids of the homologous chromosomes
occurs at the chiasmata. This process is called crossing over
or recombination.
 Diplotene: The homologous chromosomes start to
separate but remain attached at the chiasmata. The
nuclear envelope and nucleolus begin to break down.
 Diakinesis: The homologous chromosomes move further
apart and become more condensed. The chiasmata move
to the ends of the chromosomes. The nuclear envelope
and nucleolus disappear completely. The spindle fibers
start to form.
o Metaphase I: The bivalents align on the equatorial plane of the
cell. The spindle fibers attach to the kinetochores of each
chromosome. The orientation of each bivalent is random, which
leads to independent assortment of maternal and paternal
chromosomes.
o Anaphase I: The homologous chromosomes separate and move
to opposite poles of the cell. The sister chromatids remain
attached at their centromeres. The movement of the
chromosomes is facilitated by the shortening of the spindle
fibers.
o Telophase I: The chromosomes reach the poles and decondense
slightly. A nuclear envelope may or may not reform around each
set of chromosomes. The cytoplasm divides by cytokinesis,
resulting in two haploid daughter cells.
42
 Meiosis II: This is the equational division, in which the sister
chromatids separate and produce four haploid daughter
cells. Meiosis II consists of four sub-stages: prophase II, metaphase II,
anaphase II, and telophase II.
o Prophase II: The chromosomes condense again and become
visible. The nuclear envelope and nucleolus break down if they
were reformed in telophase I. The spindle fibers start to form
again [^2
o Metaphase II: The chromosomes align on the equatorial plane
of each cell. The spindle fibers attach to the kinetochores of
each chromatid[^1
o Anaphase II: The sister chromatids separate and move to
opposite poles of each cell. The movement of the chromosomes
is facilitated by the shortening of the spindle fibers[^1
o Telophase II: The chromosomes reach the poles and
decondense. A nuclear envelope reforms around each set of
chromosomes. The cytoplasm divides by cytokinesis, resulting in
four haploid daughter cells[^1

8. 43
Q37. Explain macromolecules with examples?
Ans. Macromolecules are very large molecules that are formed by the
polymerization of smaller molecules called monomers. Macromolecules
have high molecular weights, usually above 10,000 daltons, and low
solubility in water. Macromolecules are also known as polymers, which
means “many units” in Greek.
There are four main types of macromolecules in biology: carbohydrates,
lipids, proteins, and nucleic acids. Each type has a different structure,
function, and role in living organisms. Some examples of macromolecules
are:
 Carbohydrates: These are polymers of simple sugars, such as glucose
and fructose. Carbohydrates provide energy and structural support
to cells. They can be classified as monosaccharides (one sugar unit),
44
disaccharides (two sugar units), or polysaccharides (many sugar
units). Examples of carbohydrates are starch, glycogen, cellulose, and
sucrose.
 Lipids: These are hydrophobic (water-fearing) molecules that consist
of fatty acids and glycerol. Lipids store energy and form the main
component of cell membranes. They can be classified as fats (solid at
room temperature), oils (liquid at room temperature), phospholipids
(have a polar head and a nonpolar tail), steroids (have four fused
carbon rings), or waxes (have long fatty acid chains). Examples of
lipids are butter, olive oil, cholesterol, and beeswax.
 Proteins: These are polymers of amino acids, which are organic
molecules that have an amino group (-NH 2 ) and a carboxyl group (-
COOH). Proteins perform a wide range of functions in cells, such as
catalyzing chemical reactions, transporting substances, signaling
messages, defending against pathogens, and providing structural
support. They can be classified based on their shape, function, or
composition. Examples of proteins are enzymes, hemoglobin,
antibodies, and collagen.
 Nucleic acids: These are polymers of nucleotides, which are organic
molecules that have a nitrogenous base (adenine, thymine, cytosine,
guanine, or uracil), a pentose sugar (ribose or deoxyribose), and a
phosphate group. Nucleic acids store and transmit genetic
information in cells. They can be classified as DNA (deoxyribonucleic
acid) or RNA (ribonucleic acid). Examples of nucleic acids are
chromosomes, genes, mRNA, tRNA, and rRNA.
Macromolecules are important for life because they perform essential
functions in cells and organisms. They provide energy and materials for
growth and repair. They regulate cellular processes and interactions. They
encode and express genetic information. They enable adaptation and
evolution.
Q38. Draw the basic structure of the cell?
45
Ans. The basic structure of the cell consists of three main components:
the plasma membrane, the cytoplasm, and the nucleus. The plasma
membrane is a thin layer of phospholipids and proteins that surrounds
the cell and regulates the movement of substances in and out of the cell.
The cytoplasm is the fluid-filled space inside the cell that contains various
organelles and molecules that perform different functions. The nucleus is
a membrane-bound organelle that contains the genetic material (DNA) of
the cell and controls its activities.
Q39. What is the binomial system of nomenclature explain with an
examples?
Ans. Binomial nomenclature is the system of scientifically naming
organisms developed by Carl Linnaeus. Linnaeus published a large work,
Systema Naturae (The System of Nature), in which he attempted to
identify every known plant and animal. This work was published in various
46
sections between 1735 and 1758, and established the conventions of
binomial nomenclature, which are still used today1
.
Binomial nomenclature was established as a way to bring clarity and
consistency to the naming and classification of organisms, especially in
the context of scientific communication and research. Without a
formalized system for naming organisms, there would be confusion and
ambiguity among different languages, regions, and cultures. The common
names for a single species can vary widely and may not reflect the true
relationships among organisms12
.
Binomial nomenclature consists of two names, also called descriptors or
epithets. The first name is the generic name (or genus name) and
describes the genus that an organism belongs to. The second name is the
specific name (or specific epithet) and refers to the species of the
organism. The generic name is always capitalized, while the specific name
is written in lower-case. Both names are usually italicized or underlined to
indicate that they are scientific names written in binomial
nomenclature12
.
The generic name and the specific name together form the binomial
name (or simply binomial or binomen) of the organism. The binomial
name is unique for each species and follows certain rules of
nomenclature. The names are often based on Latin or Greek words that
describe some characteristics or features of the organism. Sometimes, the
names may also honor a person, a place, or a historical event related to
the organism12
.
The generic name of binomial nomenclature refers to the taxonomic rank
of genus, which is a group of closely related species that share some
common traits. The genus is part of a larger hierarchy of classification that
includes family, order, class, phylum, kingdom, and domain. The generic
name indicates the evolutionary and phylogenetic relationships among
organisms within a genus and across different genera12
.
47
The specific name of binomial nomenclature refers to the taxonomic rank
of species, which is the basic unit of biological diversity. A species is a
group of interbreeding or potentially interbreeding individuals that are
reproductively isolated from other such groups. The specific name
distinguishes one species from another within the same genus and
reflects the morphological, physiological, behavioral, or genetic
differences among them12
.
In some cases, a species may be further divided into subspecies, which
are populations that have some distinct features but can still interbreed
with other populations of the same species. The subspecies name is
written after the species name as a third epithet. For example, Panthera
leo persica is the Asiatic lion, a subspecies of Panthera leo (lion)12
.
In scientific literature, the author(s) who first described and named a
species may be cited after the binomial name. This practice gives credit to
the original source and authority of the name and helps resolve any
conflicts or disputes over naming conventions12
.
Some examples of binomial names are:
 Homo sapiens (human), named by Linnaeus in 1758
 Canis lupus (gray wolf), named by Linnaeus in 1758
 Escherichia coli (a bacterium), named by Theodor Escherich in 1885
 Rosa canina (dog rose), named by Linnaeus in 1753
 Musa paradisiaca (banana), named by Linnaeus in 1753
Q40. What are basic chemical constituents of living body?
Ans. The basic chemical constituents of living body are the molecules and
atoms that make up the cells and tissues of living organisms. These
include water, proteins, lipids, carbohydrates, nucleic acids, minerals, and
trace elements12
.
Water is the most abundant chemical constituent of living body,
accounting for about 65% of the body mass. Water is essential for life
because it acts as a solvent, a medium for chemical reactions, a transport
48
agent, a lubricant, a temperature regulator, and a participant in many
metabolic processes12
.
Proteins are polymers of amino acids that perform various functions in
living body, such as catalyzing biochemical reactions, transporting
substances, signaling messages, defending against pathogens, and
providing structural support. Proteins account for about 18.5% of the
body mass12
.
Lipids are hydrophobic molecules that consist of fatty acids and glycerol.
Lipids store energy and form the main component of cell membranes.
They also serve as hormones, vitamins, and signaling molecules. Lipids
account for about 10% of the body mass12
.
Carbohydrates are polymers of simple sugars that provide energy and
structural support to living body. They can be classified as
monosaccharides (one sugar unit), disaccharides (two sugar units), or
polysaccharides (many sugar units). Examples of carbohydrates are
glucose, glycogen, starch, cellulose, and sucrose. Carbohydrates account
for about 3% of the body mass12
.
Nucleic acids are polymers of nucleotides that store and transmit genetic
information in living body. They can be classified as DNA
(deoxyribonucleic acid) or RNA (ribonucleic acid). DNA contains the
instructions for protein synthesis and inheritance. RNA helps in the
expression and regulation of genes. Nucleic acids account for about 1% of
the body mass12
.
Minerals are inorganic elements that are essential for living body. They
play important roles in maintaining fluid balance, nerve transmission,
muscle contraction, enzyme activity, bone formation, blood clotting, and
oxygen transport. Examples of minerals are calcium, phosphorus,
potassium, sodium, chlorine, magnesium, iron, zinc, copper, iodine, and
selenium. Minerals account for about 4% of the body mass12
.
Trace elements are inorganic elements that are required by living body in
very small amounts. They act as cofactors for enzymes or components of

9. 49
hormones. Examples of trace elements are chromium, cobalt, fluorine,
manganese, molybdenum, nickel, silicon, tin, and vanadium. Trace
elements account for less than 0.1% of the body mass.
Q41. Explain the different types of cell organelles with suitable diagram?
Ans. The types and functions of cell organelles vary depending on the
type of cell. For example, prokaryotic cells, such as bacteria and archaea,
have fewer and simpler organelles than eukaryotic cells, such as animals,
plants, fungi, and protists. Prokaryotic cells lack a nucleus and other
membrane-bound organelles, except for ribosomes and sometimes
plasmids, flagella, pili, and capsules.
The following table summarizes some of the common types of cell
organelles found in eukaryotic cells, their structures, and their
functions123
:
Organelle Structure Function
Nucleus
A spherical or oval-shaped
organelle enclosed by a
double membrane called
the nuclear envelope. The
nucleus contains the
genetic material (DNA) of
the cell organized into
chromosomes. The
nucleus also contains a
dense structure called the
nucleolus where
ribosomal RNA (rRNA) is
synthesized.
The nucleus controls the
activities of the cell by
regulating gene expression.
The nucleus also stores and
protects the genetic
information of the cell. The
nucleus is the site of DNA
replication and transcription
(the synthesis of messenger
RNA or mRNA from DNA).
The nucleolus is the site of
rRNA synthesis and ribosome
assembly.
Mitochondrion
A rod-shaped or oval-
shaped organelle enclosed
The mitochondrion is the site
of cellular respiration, a
50
Organelle Structure Function
by a double membrane.
The inner membrane is
folded into numerous
projections called cristae
that increase the surface
area for chemical
reactions. The space
between the two
membranes is called the
intermembrane space. The
space inside the inner
membrane is called the
matrix. The matrix
contains mitochondrial
DNA (mtDNA), ribosomes,
enzymes, and other
molecules.
process that converts
glucose and oxygen into
carbon dioxide, water, and
energy (in the form of
adenosine triphosphate or
ATP). The mitochondrion also
plays a role in apoptosis
(programmed cell death),
calcium signaling, heat
production, and steroid
synthesis.
Endoplasmic
reticulum (ER)
A network of membranous
tubules and sacs that
extends from the nuclear
envelope throughout the
cytoplasm. The ER can be
divided into two types:
smooth ER and rough ER.
Smooth ER lacks
ribosomes on its surface
and appears smooth
under a microscope.
The smooth ER is involved in
lipid synthesis, carbohydrate
metabolism, detoxification of
drugs and toxins, calcium
storage and release, and
steroid hormone production.
The rough ER is involved in
protein synthesis, especially
for proteins that are destined
for secretion or insertion into
membranes. The rough ER
51
Organelle Structure Function
Rough ER has ribosomes
attached to its surface and
appears rough under a
microscope.
also modifies proteins by
adding sugar groups
(glycosylation) or folding
them into their correct
shapes with the help of
chaperone proteins.
Golgi
apparatus
A stack of flattened
membranous sacs called
cisternae that are located
near the nucleus. The
Golgi apparatus has two
faces: the cis face that
faces the ER and receives
vesicles containing newly
synthesized proteins or
lipids from the ER; and the
trans face that faces away
from the ER and
dispatches vesicles
containing modified
proteins or lipids to
various destinations in or
outside the cell.
The Golgi apparatus is
involved in modifying,
sorting, packaging, and
transporting proteins or
lipids received from the ER.
The Golgi apparatus can add
sugar groups (glycosylation),
phosphate groups
(phosphorylation), sulfate
groups (sulfation), or other
modifications to proteins or
lipids to alter their functions
or destinations. The Golgi
apparatus can also produce
lysosomes (membrane-
bound vesicles containing
digestive enzymes) or
secretory vesicles
(membrane-bound vesicles
containing substances to be
released from the cell).
52
Organelle Structure Function
Lysosome
A spherical or irregular-
shaped membrane-bound
vesicle that contains
hydrolytic enzymes that
can break down various
biomolecules such as
proteins, nucleic acids
Q42. Distinguish mitosis and meiosis?
Ans. Mitosis and meiosis are two types of cell division that occur in
eukaryotic cells. Both processes involve the duplication of the genetic
material (DNA) and the separation of the chromosomes into two daughter
cells. However, there are some key differences between mitosis and
meiosis that affect the number, type, and genetic composition of the
daughter cells123
.
Some of the main differences between mitosis and meiosis are:
53
 Mitosis produces two genetically identical daughter cells from a
single parent cell, whereas meiosis produces four genetically unique
daughter cells from a single parent cell.
 Mitosis involves one round of DNA replication and one round of cell
division, whereas meiosis involves one round of DNA replication and
two rounds of cell division.
 Mitosis maintains the same number of chromosomes (2n) in the
daughter cells as in the parent cell, whereas meiosis reduces the
number of chromosomes by half (n) in the daughter cells as
compared to the parent cell.
 Mitosis occurs in somatic cells (body cells) for growth, repair, and
asexual reproduction, whereas meiosis occurs in germ cells (sex cells)
for sexual reproduction and genetic variation.
 Mitosis does not involve crossing-over or recombination of
homologous chromosomes, whereas meiosis involves crossing-over
or recombination of homologous chromosomes during prophase I,
which creates new combinations of alleles in the daughter cells.
 Mitosis does not involve independent assortment or random
alignment of homologous chromosomes at the metaphase plate,
whereas meiosis involves independent assortment or random
alignment of homologous chromosomes at the metaphase plate
during metaphase I, which increases the genetic diversity of the
daughter cells.
 Mitosis results in diploid (2n) daughter cells that are identical to each
other and to the parent cell, whereas meiosis results in haploid (n)
daughter cells that are different from each other and from the
parent cell.
Q43. What is complete dominance and incomplete dominance?
Ans. Complete dominance and incomplete dominance are two types of
dominance relationships between alleles of a gene. In complete
dominance, one allele is dominant over the other allele in the pair, and
54
the dominant allele determines the phenotype of the heterozygote. For
example, in pea plants, the allele for purple flowers (P) is dominant over
the allele for white flowers (p), so a plant with the genotype Pp will have
purple flowers12. In incomplete dominance, neither allele in the pair is
dominant or recessive, and the phenotype of the heterozygote is a blend
of the phenotypes of the homozygotes. For example, in snapdragons, the
allele for red flowers ® and the allele for white flowers (W) show
incomplete dominance, so a plant with the genotype RW will have pink
flowers.
Q44. What is the Role of micro and macronutrients in plants?
Ans. Micro and macronutrients are essential elements that plants need to
grow and develop properly1
Macronutrients are required in large
amounts and include carbon, hydrogen, oxygen, nitrogen, phosphorus,
sulfur, calcium, and potassium12
. These elements are involved in the
formation of carbohydrates, proteins, nucleic acids, and other
biomolecules, as well as the regulation of metabolic activities and osmotic
potential23
Micronutrients are required in smaller amounts and include
iron, zinc, boron, manganese, copper, molybdenum, nickel, chlorine, and
silicon12
. These elements are involved in the activation or inhibition of
enzymes, the synthesis of DNA and RNA, the maintenance of cell
structure and function, and the protection against stress23
. Inadequate
supplies of these nutrients can lead to stunted growth, slow growth,
chlorosis, or cell death.
Q45. Differentiate between cell wall and cell membrane?
Ans. Cell wall and cell membrane are two types of outermost boundaries
found in cells. Cell wall is the outermost boundary of bacteria, fungi and
plant cells. Cell membrane is the outermost boundary of animal cells. Cell
membrane can be identified on the inner side of the cell wall, in cells
which possess the cell wall1
. Some of the differences between cell wall
and cell membrane are:

10. 55
Cell Wall Cell Membrane
Present only in plants, fungi and some
bacteria and archaea234
.
Present in all living
organisms234
.
Composed mainly of cellulose (in plants),
chitin (in fungi), peptidoglycan (in bacteria)
or other polysaccharides234
.
Composed mainly of lipids
and proteins234
.
Thick and rigid and has a fixed shape234
.
Thin and flexible and can
change its shape according
to the cell234
.
Protects the cell from physical damage and
invading pathogens234
.
Regulates the entry and exit
of substances into and out of
the cell234
.
Allows free passage of molecules through
it234
.
Selectively permeable and
controls the movement of
molecules across it.
Q46. Differentiate between structural and functional features of
prokaryotic and eukaryotic cells?
Ans. Prokaryotic and eukaryotic cells are the two main categories of cells
present in living beings. Prokaryotes are always unicellular, whereas
eukaryotic cells can be multicellular or unicellular1
. Some of the
differences between prokaryotic and eukaryotic cells are:
Prokaryotic Cells Eukaryotic Cells
They do not have a nucleus. Their
genetic material (DNA or RNA) is
free-floating in the cytoplasm234
.
They have a nucleus surrounded by a
nuclear membrane. Their genetic
material (DNA) is enclosed within the
56
Prokaryotic Cells Eukaryotic Cells
nucleus234
.
They do not have membrane-
bound organelles such as
mitochondria, chloroplasts,
endoplasmic reticulum, Golgi
apparatus, etc234
.
They have membrane-bound
organelles such as mitochondria,
chloroplasts, endoplasmic reticulum,
Golgi apparatus, etc234
.
They have a simple cell
structure with a cell wall, cell
membrane, cytoplasm,
ribosomes and plasmids234
.
They have a complex cell
structure with a cell wall (in plants and
fungi), cell membrane, cytoplasm,
ribosomes and various other
organelles234
.
They are generally smaller in
size (0.1-5 micrometers) and
have a circular or rod-shaped
morphology234
.
They are generally larger in size (10-
100 micrometers) and have a variety of
shapes and forms234
.
They reproduce by binary fission,
a simple process of cell
division234
.
They reproduce by mitosis or meiosis,
complex processes of cell division that
involve chromosomal segregation and
recombination
Q47. Write the functions of Mitochondria.
Ans. Mitochondria are membrane-bound organelles present in the
cytoplasm of all eukaryotic cells, that produce adenosine triphosphate
(ATP), the main energy molecule used by the cell1
. Some of the functions
of mitochondria are:
57
 They produce energy through the process of oxidative
phosphorylation, which involves the breakdown of nutrients and the
generation of ATP molecules234
.
 They regulate the metabolic activity of the cell by sensing and
responding to changes in nutrient availability, oxygen levels, and
cellular stress4
.
 They promote the growth of new cells and cell multiplication by
providing energy and biosynthetic intermediates4
.
 They help in detoxifying ammonia in the liver cells by converting it
into urea, which can be excreted by the kidneys4
.
 They play an important role in apoptosis or programmed cell death
by releasing cytochrome c and other pro-apoptotic factors that
activate a cascade of enzymes called caspases.
Q48. Write the functions of Nucleus.
Ans. Nucleus is a double-membraned organelle that contains the genetic
material (DNA) and other instructions required for cellular processes1
.
Some of the functions of nucleus are:
 It stores the cell’s hereditary information and controls the cell’s
growth and reproduction by regulating gene expression and initiating
cellular division123
.
 It produces different types of RNA from DNA by the process of
transcription. RNA molecules are involved in protein synthesis, gene
regulation, and other cellular functions123
.
 It contains a structure called nucleolus, which is responsible for the
synthesis and assembly of ribosomes. Ribosomes are the sites of
protein translation in the cytoplasm123
.
 It maintains the integrity and stability of the genome by repairing
DNA damage, preventing mutations, and organizing chromatin23
.
 It participates in cellular signaling by responding to external stimuli
and regulating the activity of nuclear receptors.