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8m Biology.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:
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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.
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.
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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.
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
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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.
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
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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.
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.
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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
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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.
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
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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 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
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secreted by endocrine glands into the bloodstream and travel
to their target cells, where they bind to specific receptors and
elicit a physiological 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
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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 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
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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 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.
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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 carbon dioxide
Obtain carbon from organic sources like
carbohydrates, lipids, and proteins
Are also called “self
feeders” or
“primary
producers”
Are also called “other feeders” or
“consumers”
Are usually plants Are usually animals
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Autotroph
Organisms Heterotroph Organisms
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
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with two recessive alleles for straight hair (cc) will have
straight hair.
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
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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).
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
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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.
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
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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), 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
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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 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
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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
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various habitats across the globe. They also documented the
patterns and processes of biodiversity distribution, evolution,
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:
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Q21. Differentiate between photosynthesis and respiration in
plant.
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
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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
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.
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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)
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.
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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
5. 33
archaea, 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
34
Prokaryote Organisms Eukaryote Organisms
Mostly unicellular and
extremophilic
Can be either unicellular or
multicellular and diverse
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
35
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 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
36
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.
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
37
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.
Q27. Draw the flow chart of Krebs cycle.
38
Q28. Draw a flowchart of photosynthesis cycle in reference to
synthesis of glucose in plant.
39
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.
40
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.
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,
6. 41
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 (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
42
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 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
43
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.
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
44
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 unit or centimorgan is equivalent to
45
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.
46
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.
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.
47
Q35. What is the cell? Differentiate between plant cell and
animal cell?
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,
48
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.
Animal cells have centrioles that are
involved in organizing the spindle fibers
during cell division.
plant cells do not have
centrioles.
7. 49
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 tetrads. This process is called
50
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
51
reform around each set of chromosomes. The cytoplasm
divides by cytokinesis, resulting in two haploid daughter
cells.
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
52
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
53
structural support to cells. They can be classified as
monosaccharides (one sugar unit), 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
54
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?
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.
55
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 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.
56
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
.
8. 57
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?
58
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 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
59
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 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
60
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 by a double
membrane. The inner
membrane is folded
into numerous
projections called
cristae that increase
the surface area for
chemical reactions.
The mitochondrion is the
site of cellular
respiration, a process
that converts glucose and
oxygen into carbon
dioxide, water, and
energy (in the form of
adenosine triphosphate
or ATP). The
mitochondrion also plays
61
Organelle Structure Function
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.
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. Rough ER
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
62
Organelle Structure Function
has ribosomes
attached to its surface
and appears rough
under a microscope.
insertion into
membranes. The rough
ER 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
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
63
Organelle Structure Function
various destinations in
or outside the cell.
(membrane-bound
vesicles containing
digestive enzymes) or
secretory vesicles
(membrane-bound
vesicles containing
substances to be released
from the cell).
Lysosome
A spherical or
irregular-shaped
membrane-bound
vesicle that contains
hydrolytic enzymes
that can break down
various biomolecules
such as proteins,
nucleic acids
64
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:
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
9. 65
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 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
66
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:
67
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
68
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 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
69
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:
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
.
70
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.
