The cell is the basic unit of life. All organisms are made up of cells (or in some cases, a single cell). Most cells are very small; most are invisible without using a microscope. Cells are covered by a cell membrane and come in many different shapes. The contents of a cell are called the protoplasm.

1. *

2. Anatomy of animal cell

3. *The cell
The cell is the smallest structural, functional, and
biological unit of all living organisms which can
capable of biosynthesis, replication and energy
transformation.
They are often called the ‘building blocks of life’.

4. *Cytology is the scientific study of cellular structure and
function. Organisms can be classified as unicellular
(consisting of a single cell; including bacteria) or
multicellular (including plants and animals).
*While the number of cells in plants and animals varies
from species to species, humans contain about 100 trillion
(1014) cells.
*All cells arise from existing cells by the process of cell
division, in which one cell divides into two identical cells.
*Different types of cells fulfil unique roles that support
homeostasis and contribute to the many functional
capabilities of the human organism.

5. *Most plant and animal cells are visible only
under the microscope, with dimensions between
1 and 100 µm.
*Animal cell contains membrane bound nucleus,
it also contains other membrane bound cellular
organelles. These cellular organelles carry out
specific functions that are necessary for the
normal functioning of the cell.

6. *

7. *The cell membrane (also called the plasma membrane) is
a biological membrane that surrounds the cytoplasm of a
cell which covers the cell.
*In short, it is the outer boundary of the cell. It is a thin,
elastic structure about 7.5 to 10 nm in thickness.
*It separates the internal environment (inside the cell)
from the external environment (outside the cell).

8. *The plasma membrane is made up of lipid bilayer, which
contains lipid molecules—phospholipids, cholesterol, and
glycolipids.
*The bilayer arrangement found because the lipids are
amphipathic molecules, which means that they have both
polar and nonpolar parts.
*The polar part is made up of phosphate containing “head,”
which is hydrophilic (hydro means water; philic means
loving). The nonpolar part is made up of two long fatty acid
“tails,” which are hydrophobic (-phobic means fearing).

9. * FUNCTIONS
*The membrane allow the passage of different
nutrients and electrolyte ions into and out of a cell.
*The plasma membrane also plays a vital role in
communication between cells to cells.
*Plasma membranes also contain proteins that allow
cells to detect external signalling molecules such as
hormones.

10. *
*The intracellular substance in which all cell
organelles are suspended is known as cytoplasm.
*Cytoplasm is a viscous, transparent, gel like
semisolid fluid containing 75-90% water,
proteins, carbohydrates, lipids, organic
substances including amino acids, sugars
polysaccharides and inorganic substances such
as mineral ions.

11. *
The nuclear membrane is composed of two membranes i.e. inner
and outer nuclear membranes.
The inner membrane surrounds and contains the nucleoplasm and
its materials.
The outer membrane is continuous with the endoplasmic reticulum
(ER). Both are made up of phospholipid bilayers and nuclear pores.
These pores allow the passage of materials from the nucleoplasm
into the cytoplasm. For example, messenger RNA (mRNA) and
various proteins.

12. NUCLEOPLASM
The fluid medium of the nucleus is called the nucleoplasm.
It consists of proteins, the nucleic acids DNA, RNA,
enzymes, and other chemicals of the nucleus.
CHROMATIN
The cells of the human body contain 46 chromosomes
(22 pairs of autosomes and one pair of sex chromosomes:
one member of each pair comes from the father and one
member from the mother).

13. The egg cell (ovum) and
the sperm cell contain one
half that number or 23
chromosomes.
Chromosomes are
supercoiled structures of
chromatins and act as
genetic material of the cell.
Each chromatin consists of
million numbers of DNA
molecules. Each DNA
molecule is made up of
sequence of amino acids.

14. *
*It is a complex system composed of membrane bound
cavities. The cavities are channel-like structures called
as cisternae which are used to store and transport
materials made by the cell. The ER is attached to the
outer membrane of the nuclear membrane.
*The endoplasmic reticulum ER is divided in to two types.
1] Rough (granular) ER composed of ribosomes;
2] Smooth (agranular) ER has no ribosomes.

16. *
*All cells have a rough endoplasmic
reticulum. It is also called as granular
endoplasmic reticulum because it contains
ribosomes.
*The rough ER is the site of protein
biosynthesis. The cavities of the rough ER
work in the separation and transport of
these proteins.

17. *
*Smooth (or agranular) endoplasmic reticulum does not
have attached ribosomes. It also differs in function.
*Only certain cells have the smooth ER including adrenal
gland, sex glands (ovary and testes), adipose tissues,
liver, small intestine, pancreas etc.
*Smooth ER performs biosynthesis of steroidal hormones,
sex hormones digestive enzymes, fatty acid,
phospholipids, triglycerides and cholesterol.
*Enzymes within the smooth ER can detoxify a variety of
chemicals including alcohol and certain drugs.

18. *
*There are many, many ribosomes in the cell because they are
so essential to cell function.
*Free ribosomes are small tiny granules distributed throughout
the cytoplasm and some are attached to the rough-granular
endoplasmic reticulum.
*They are the actual sites of protein synthesis. Free ribosomes
synthesise proteins which are utilized for the metabolism of the
cell and growth.
*The attached ribosomes are the sites for the protein synthesis
to be secreted by the cell. Ribosomes are composed of
ribosomal RNA (rRNA) and several ribosomal proteins.
*Messenger RNA (mRNA) attaches to ribosomes during proteins
synthesis.

19. *
*The Golgi apparatus is also called as Golgi body. The shape of
Golgi apparatus is like a tea cup. It may be attached to the
endoplasmic reticulum.
*They are covered by two membranes: Inner membrane and
outer membrane. The inner membrane is composed of number
of folds/cavities called as cisterns. The Golgi apparatus also
consists of secretory vesicles.

20. * Carbohydrates synthesis like glucose takes place in the Golgi
apparatus.
*Proteins formed by ribosomes are stored in the secretory
vesicles of Golgi apparatus.
*In the pancreas, the digestive enzymes are stored in Golgi
apparatus and then are secreted.
*The secretory vesicles of Golgi bodies which are composed of
digestive enzymes further develop in to Lysosomes.
*The Golgi bodies also perform processing, sorting, packaging
and transport of lipids and proteins to cell membrane,
lysosomes, and secretory vesicles.
Functions

21. All the proteins exported from the cell follow the similar route
Ribosomes (site of protein synthesis) Rough ER Transport vesicles
Golgi apparatus Secretory vesicles
Proteins release to outside of the cell by exocytosis

23. *
Mitochondrion is a bean-
shaped organelle that acts
as a “energy transformer” of
the cell.
They are the site of cellular
respiration and energy
metabolism. They act by
generating ATP, an energy
rich molecule.

24. *They are usually 3-4 µm in size. The number of
mitochondria varies in different types of cells.
*Cells with high metabolic activity have high number of
mitochondria, while those with low metabolic activity
have a lower number.
*There are about 1600-2000 mitochondria present in liver
cells, muscle cells, kidney, while sperm cells contain
only 20-24.
*Mitochondria are composed of two membranes. The
outer membrane is smooth gives its capsule shape to
mitochondrion;
*while the inner membrane is arranged in a series of folds
called as cristae. The central cavity of a mitochondrion
is called as the matrix.

25. *The matrix contains DNA, some proteins, ribosomes and
several enzymes required for metabolism of carbohydrates,
lipids and amino acids (citric acid cycle, β-oxidation, oxidative
phosphorylation).
*These reactions convert nutrient molecules (such as glucose)
into ATP, which provides cellular energy to the cell. Oxygen
molecules are required during cellular respiration, which is
why you must constantly breathe it in.
The cellular respiration can be stated as follows:
Food (like glucose) + oxygen Energy + waste+ water
C6H12O6 + 6O2 ATP + 6CO2 + 6H2O
Most of the energy-producing reactions, which occur in
the mitochondria, take place on the surface of the
cristae. For this reason, the mitochondria are known as
the powerhouses of the cell.