Animal cells are the basic unit of life in animals. They are eukaryotic cells that lack a cell wall and contain a nucleus and other organelles that carry out specialized functions. Unlike plant cells, animal cells do not contain chloroplasts and must obtain nutrients from external sources. The organelles in animal cells include the mitochondria, which produce energy, and the endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, and other structures that help the cell carry out its functions. Animal cells are typically diploid and undergo meiosis to produce haploid gametes during sexual reproduction.

1. THE CELL
BASIC UNIT OF LIFE IN ORGANISMS
DR. HIMANI SINGH, M.Sc., Ph.D (BIOTECHNOLOGY)

3. DEFINITION:- “An animal cell is a type of eukaryotic cell that lacks a cell wall and has
a true, membrane-bound nucleus along with other cellular organelles.”
ANIMAL CELL OVERVIEW:-
• Animals, fungi, and protists all have eukaryotic cells, Eukaryotic cells are
distinguished by the presence of a nucleus and other membrane-bound
organelles.
• Animal cells, do not have a cell wall. Instead, multicellular animals have
a skeleton which provides support for their tissues and organs. Likewise,
animal cells also lack the chloroplasts.
• Animal cells are considered heterotrophic, this means animal cells must
obtain nutrients from other sources, by eating plant cells or other animal
cells.
• All eukaryotic cells, animal cells have mitochondria. These organelles are
used to create ATP from various sources of energy including carbohydrates,
fats, and proteins.
• Besides mitochondria, many other organelles are found within animal cells
which help them carry out the many functions required for life (Nucleus ,
ribosomes, Endoplasmic Reticulum, Golgi Apparatus, lysosomes,
peroxisomes)
• Most animal cells are diploid, meaning that their chromosomes exist in
homologous pairs. In sexual reproduction, the cellular process
of meiosis is first necessary so that haploid daughter cells, or gametes, can
be produced. Two haploid cells then fuse to form a diploid zygote, which
develops into a new organism as its cells divide and multiply.

4. PLANT CELL

5. • Plant cells are the basic unit of life in organisms of the kingdom Plantae.
They are eukaryotic cells, which have a true nucleus along with
specialized structures called organelles that carry out different functions.
Plant cells have special organelles called chloroplasts which create sugars
via photosynthesis.
• Plant cells are differentiated from the cells of other organisms by their cell
walls, chloroplasts, and central vacuole. The chloroplasts within plant cells
can undergo photosynthesis, to produce glucose. In doing so, the cells
use carbon dioxide and they release oxygen.
• Plants are considered autotrophic because they produce their own food
and do not have to consume any other organisms. Specifically, plant cells
are photoautotrophic because they use light energy from the sun to
produce glucose.
• The other components of a plant cell, the cell wall and central vacuole,
work together to give the cell rigidity. The plant cell will store water in the
central vacuole, which expands the vacuole into the sides of the cell. The
cell wall then pushes against the walls of other cells, creating a force
known as turgor pressure.
• Turgor pressure between cells allows plants to grow tall and reach more
sunlight.

6. NUCLEUS
• The nucleus contains a cell’s deoxyribonucleic
acid (DNA), its genetic material. DNA contains
instructions for making proteins, which controls all
of the body’s activities.
• In the nucleus, DNA is tightly winded around
histones, which are proteins, to form structures
called chromosomes. The nucleus regulates
which genes are expressed in the cell, which
controls the cell’s activity and functioning
and will be different depending on the type of
cell.
• DNA is located in the nucleolus region of the
nucleus, where ribosomes are made. The
nucleus is surrounded by a nuclear envelope
(also called nuclear membrane), which separates
it from the rest of the cell.
• The nucleus also regulates the growth and
division of the cell. When the cell is preparing to
divide during mitosis, the chromosomes in the
nucleus duplicate and separate, and
two daughter cells are formed.
• Organelles called centrosomes help organize
DNA during cell division. Cells usually have one
nucleus each.

7. PLASMA MEMBRANE
• All living cells have a plasma membrane that encloses their contents. In prokaryotes, the membrane
is the inner layer of protection surrounded by a rigid cell wall. Eukaryotic animal cells have only the
membrane to contain and protect their contents. These membranes also regulate the passage of
molecules in and out of the cells.
• The plasma membrane separates the interior of the cell from the extracellular environment. Its
predominant components are proteins and lipids, the fundamental structure of the membrane is
the phospholipid bilayer, plasma membranes consist of approximately 50% lipid and 50% protein by
weight, with the carbohydrate portions of glycolipids and glycoproteins constituting 5 to 10% of the
membrane mass.
• The plasma membrane, also called the cell membrane, In bacterial and plant cells, a cell wall is
attached to the plasma membrane on its outside surface.

8. GOLGI APPARATUS
• The Golgi apparatus, also called the Golgi complex or Golgi body, is also made up of
cisternae, but the cisternae are not interconnected like those of the ER. The Golgi
apparatus receives proteins from the ER and folds, sorts, and packages these proteins
into vesicles.
• It resides at the intersection of the secretory, lysosomal, and endocytic pathways. It is of
particular importance in processing proteins for secretion, containing a set
of glycosylation enzymes that attach various sugar monomers to proteins as the proteins
move through the apparatus.
• It was identified in 1897 by the Italian scientist Camillo Golgi and was named after him in
1898
Synthesis of golgi bodies

9. MITOCHONDRIA
• The process of cellular respiration occurs in
the mitochondria. During this process, sugars
and fats are broken down and energy is released
in the form of adenosine triphosphate (ATP). ATP
powers all cellular processes, and mitochondria
produce a cell’s ATP, so mitochondria
are commonly known as “the powerhouse of
the cell”.
• It has a double membrane, the inner part being
folded inwards to form layers (cristae).
• Mitochondria are commonly between 0.75 and
3 μm² in area but vary considerably in size and
structure
• In addition to supplying cellular energy,
mitochondria are involved in other tasks, such
as signaling, cellular differentiation, and cell
death, as well as maintaining control of the cell
cycle and cell growth.
• The first observations of intracellular structures
that probably represented mitochondria were
published in the 1840s. Richard Altmann, in
1890, established them as cell organelles and
called them "bioblasts".The term "mitochondria"
was coined by Carl Benda in 1898.

10. ENDOPLASMIC RETICULUM
• The endoplasmic reticulum (ER) is a network of membranous sacs called cisternae that
branches off from the outer nuclear membrane. It modifies and transports proteins that are
made by ribosomes. There are two kinds of endoplasmic reticulum, smooth and
rough. Rough ER has ribosomes attached. Smooth ER does not have ribosomes attached
and has functions in making lipids and steroid hormones and removing toxic substances.

11. RIBOSOMES
• Ribosomes are where proteins are synthesized. They are found within all cells, including
animal cells. In the nucleus, a sequence of DNA that codes for a specific protein is copied
onto a complementary messenger RNA (mRNA) chain. The mRNA chain travels to
the ribosome via transfer RNA (tRNA), and its sequence is used to determine the
correct placement of amino acids in a chain that makes up the protein. In animal cells,
ribosomes can be found freely in a cell’s cytoplasm, or attached to membranes of
the endoplasmic reticulum.
• FUNCTION: Ribosomes are a cell structure that makes protein. Protein is needed for
many cell functions such as repairing damage or directing chemical processes. Ribosomes
can be found floating within the cytoplasm or attached to the endoplasmic reticulum

12. PEROXISOMES
• Peroxisome is a membrane-
bound organelle (formerly known as
a microbody), found in the cytoplasm of
virtually all eukaryotic cells. Peroxisomes are
oxidative organelles. Frequently, molecular
oxygen serves as a co-substrate, from
which hydrogen peroxide (H2O2) is then
formed. Peroxisomes owe their name to
hydrogen peroxide generating and
scavenging activities. They perform key roles
in lipid metabolism and the conversion
of reactive oxygen species.
LYSOSOMES
The main function of these microbodies is
digestion. Lysosomes break down cellular
waste products and debris from outside the
cell into simple compounds, which are
transferred to the cytoplasm as new cell-
building materials.

13. MICROFILAMENTS
•Microfilaments are solid rods made
of globular proteins called actin.
•Microfilaments, also called actin
filaments, are protein filaments in
the cytoplasm of eukaryotic cells
that form part of the cytoskeleton.
• Microfilaments are usually about
7 nm in diameter and made up of
two strands of actin.
•Microfilament functions include
cytokinesis, amoeboid movement,
cell motility, changes in cell shape,
endocytosis and exocytosis, cell
contractility, and mechanical
stability
MICROTUBULES
•Microtubules are major
components of the cytoskeleton.
They are found in all eukaryotic
cells, and they are involved in
mitosis, cell motility, intracellular
transport, and maintenance of cell
shape.
•Microtubules are composed of
alpha- and beta-tubulin subunits
assembled into linear protofilaments.
•Microtubules can grow as long as 50
micrometres and are highly dynamic.
The outer diameter of a microtubule
is between 23 and 27 nm while the
inner diameter is between 11 and 15
nm

14. CILIA AND FLAGELLA:- For single-celled eukaryotes, cilia and flagella are essential
for the locomotion of individual organisms. In multicellular organisms, cilia function
to move fluid or materials past an immobile cell as well as moving a cell or group of
cells.
ENDOSOMES AND ENDOCYTOSIS:- Endosomes are membrane-bound vesicles,
formed via a complex family of processes collectively known as endocytosis, and
found in the cytoplasm of virtually every animal cell. The basic mechanism of
endocytosis is the reverse of what occurs during exocytosis or cellular secretion. It
involves the invagination (folding inward) of a cell's plasma membrane to surround
macromolecules or other matter diffusing through the extracellular fluid.

15. CENTRIOLES
•Centrioles are cylindrical, self-replicating organelles composed mainly of a protein called
tubulin made up of microtubules and Centrioles are found in most eukaryotic cells. They
appear to help in organizing cell division.
•A bound pair of centrioles, surrounded by a shapeless mass of dense material, called the
pericentriolar material, makes up a structure called a centrosome

16. INTERMEDIATE FILAMENTS
•Intermediate filaments are one of three types of cytoskeletal elements. The other
two are thin filaments (actin) and microtubules. Frequently the three components
work together to enhance both structural integrity, cell shape, and cell and
organelle motility. Intermediate filaments are stable, durable.
•Ranging in size from 8 to 12 nanometers

17. VESICLES
Vesicles are small spheres of a lipid bilayer,
which also makes up the cell’s outer
membrane. They are used for transporting
molecules throughout the cell from one
organelle to another and are also involved
in metabolism. Specialized vesicles called
lysosomes contain enzymes that digest large
molecules like carbohydrates, lipids, and
proteins into smaller ones so that they can be
used by the cell.
CYTOSOL
The cytosol is the liquid contained within cells. Cytosol and all the organelles within
it, except for the nucleus, are collectively referred to as a cell’s
cytoplasm. This solution is mostly made of water, but also contains ions like
potassium, proteins, and small molecules. The pH is generally neutral, around 7.
CYTOSKELETON
The cytoskeleton is a network of filaments and tubules found throughout the
cytoplasm of the cell. It has many functions: it gives the cell shape, provides
strength, stabilizes tissues, anchors organelles within the cell, and has a role in cell
signaling. There are three types of cytoskeletal filaments: microfilaments,
microtubules, and intermediate filaments. Microfilaments are the smallest, while
microtubules are the biggest.

18. ANIMAL CELLS FUNCTION
• Cells carry out all the processes of the body including producing and storing energy,
making proteins, replicating the DNA, and transportation of molecules through the
body. Cells are highly specialized to carry out specific tasks. For example,
the heart has cardiac muscle cells that beat in unison. Digestive tract cells have
cilia, which are finger-like projections that increase surface area for the absorption
of nutrients during digestion. Each cell type has the organelles suited to its
particular task.
• There are over 200 different types of cells in the human body. Red blood cells
contain hemoglobin, the molecule that carries oxygen, and they have no nuclei; this
is a specialization that allows each red blood cell to carry as much oxygen within it
as possible.
• Multiple cells form tissues. These groups of cells carry out a specific function. In
turn, groups of similar tissues form the body’s organs, such as the brain,
lungs, and heart. Organs work together in organ systems, like the nervous
system, digestive system, and circulatory system. Organ systems vary depending
on the species.
• For example, insects have open circulatory systems, where blood is pumped
directly into body cavities and surrounds their tissues. Vertebrates such as fish,
mammals, and birds, on the other hand, have closed circulatory systems. Their
blood is enclosed within blood vessels where it travels to target tissues. In this way,

19. PLANT CELL
CHLOROPLASTS
• Chloroplasts are found only in plant
and algae cells. These organelles carry out the
process of photosynthesis, where the
photosynthetic pigment chlorophyll captures
the energy from sunlight, converts it, and stores it in
the energy-storage molecules ATP and NADP while
freeing oxygen from water in plant and algal cells.
They then use the ATP and NADPH to make
organic molecules from carbon dioxide in a process
known as the Calvin cycle.
• Chloroplasts carry out a number of other functions,
including fatty acid synthesis, much amino
acid synthesis, and the immune response in plants.
• They are oval-shaped and have two membranes:
an outer membrane, which forms the external
surface of the chloroplast, and an inner membrane
that lies just beneath. Between the outer and inner
membrane is a thin intermembrane space about 10-
20 nanometers wide. Within the other membrane,
there is another space called the stroma, which is
where chloroplasts are contained.
• Chloroplasts themselves contain many flattened
disks called thylakoids, and these have a high
concentration of chlorophyll and carotenoids, which
capture light energy. The molecule chlorophyll also
gives plants their green color. Thylakoids are
stacked on top of one another in vascular plants in

20. CELL WALL
The cell wall is a tough layer found on the outside of the plant cell that gives it strength and also
maintains high turgidity. In plants, the cell wall contains mainly cellulose, along with other
molecules like hemicellulose, pectin, and lignins. The composition of the plant cell wall
differentiates it from the cell walls of other organisms.
For example, fungi cell walls contain chitin, and bacterial cell walls contain peptidoglycan, and
these substances are not found in plants. The main difference between plant and animal
cells is that plant cells have a cell wall while animal cells do not. Plant cells have a primary
cell wall, which is a flexible layer formed on the outside of a growing plant cell, and a secondary
cell wall, a tough, thick layer formed inside the primary plant cell wall when the cell is mature.

21. VACUOLES
• Plant cells are unique in that they have a large central vacuole. A vacuole is a small sphere
of plasma membrane within the cell that can contain fluid, ions, and other
molecules. Vacuoles are basically large vesicles. They can be found in the cells of many
different organisms, but plant cells characteristically have a large vacuole that can take up
anywhere from 30-80 percent of the cell.
• The central vacuole of a plant cell helps maintain its turgor pressure, which is the pressure of
the contents of the cell pushing against the cell wall. A plant thrives best when its cells have
high turgidity, and this occurs when the central vacuole is full of water. If turgor pressure in
the plants decreases, the plants begin to wilt. Plant cells fare best in hypotonic solutions,
where there is more water in the environment than in the cell; under these conditions, water
rushes into the cell by osmosis , and turgidity is high.
• Animal cells, on the other hand, can lyse if too much water rushes in; they fare better
in isotonic solutions, where the concentration of solutes in the cell and in the environment is
equal and net movement of water in and out of the cell is the same.

22. PLANT CELL TYPES
There are five types of plant cells, each with
different functions:
Parenchyma cells are the majority of cells in a
plant. They are found in leaves and carry out
photosynthesis and cellular respiration, along with
other metabolic processes. They also store
substances like starches and proteins and have a
role in plant wound repair.
Collenchyma cells provide support to growing
parts of a plant. They are elongated, have thick
cell walls, and can grow and change shape as a
plant grows.
Sclerenchyma cells are hard cells that are the
main supporting cells in the areas of a plant that
have ceased growing. Sclerenchyma cells are
dead and have very thick cell walls.
Xylem cells transport mostly water and a few
nutrients throughout a plant, from the roots to the
stem and leaves.
Phloem cells transport nutrients made during
photosynthesis to all parts of a plant. They
transport sap, which is a watery solution high in
sugars.

23. PLANT CELL FUNCTIONS
Plant cells are the basic building block of plant life, and they carry out all of the functions
necessary for survival. Photosynthesis, the making of food from light energy, carbon dioxide,
and water, occurs in the chloroplasts of the cell. The energy molecule adenosine triphosphate
(ATP) is produced through cellular respiration in the mitochondria.

24. EMAIL ID : himanisinghbt@gmail.com
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