Cells are the basis of life—the basic structural unit of living things. Molecules such as water and amino acids are not alive but cells are! All life is comprised of cells of one type or another. One of the hallmarks of living systems is the ability to maintain homeostasis, or a relatively constant internal state. The cell is the first level of complexity able to maintain homeostasis, and it is the unique structure of the cell that enables this critical function. In this section of the course, you will learn about the cell and all the parts that make it functional. You will also focus on the cell membrane, which is the structure that surrounds the cell and separates its internal environment from the external environment. It is a critical component because it controls what can enter and exit the cell. This section will also describe how cells reproduce to maintain homeostasis.Cells are the basis of life—the basic structural unit of living things. Molecules such as water and amino acids are not alive but cells are! All life is comprised of cells of one type or another. One of the hallmarks of living systems is the ability to maintain homeostasis, or a relatively constant internal state. The cell is the first level of complexity able to maintain homeostasis, and it is the unique structure of the cell that enables this critical function. In this section of the course, you will learn about the cell and all the parts that make it functional. You will also focus on the cell membrane, which is the structure that surrounds the cell and separates its internal environment from the external environment. It is a critical component because it controls what can enter and exit the cell. This section will also describe how cells reproduce to maintain homeostasis.

1. THE CELL
Represented by- Radiate

2. Introduction
 The cell is the functional and structural unit of living
body.
Cell
Tissue
Organ
Organ
system
Living
body

3. 3D model of a typical animal cell

4. Introduction
 Many cells are group together to form tissue.
 Many tissue group together to form organ.
 Many organ group together to form organ system.
 Many organ system group together and co-ordinate to
form of living body.
 Cell of different tissue perform different function.
 A cell is of microscopic jelly like structure which is
known as ‘Protoplasm’ (nucleus, mitochondria etc.).
 Protoplasm are held together by a cell membrane are
plasma membrane.
 Cell possess the quality of all living matter, include in
those of cell preservation and reproduction.

5. Labeled diagram of a typical animal cell

6. Plasma membrane or Cell membrane
 Plasma (cell) membrane is the outer surface of the cell.
 It is covering of the cell which is 0.1  in thickness.
 It can be seen only under electron microscope.
 It is formed of 40% lipids and 60% protein.
 It is selectively formidable for certain substance.
 It has osmotic properties (low concentrations to high
concentrations).
 The cell membrane is a double layer of phospholipids
molecules.
 Proteins in the cell membrane provide structural support,
form channels for passage of materials, act as receptor
sites, function as carrier molecules, and provide
identification markers.

8. 1. Nucleus
 It is the largest structure of the cell which almost
present of centre of cell.
 It is more or less spherical in shape, it is bounded
by nuclear membrane which protect the nucleus.
 The nucleus contains:-
(a)
Nucleolus
(b)
Chromatin

9. (a) Nucleolus
 It is highly coiled filamentous structure present in the
nucleus.
 It has no membrane surrounding it.
 It contains numerous granules.
 Nucleus is responsible for ribosomal RNA synthesis.
 It contains one or more nucleoli, which is essential for
growth, metabolism, reproduction and transmission.
 It store ribosomal RNA and control the synthesis of
ribose and protein.

11. (b) Chromatin
 These are fibrous thread like structure which are
presented in nucleus.
 They are composed of DNA and protein.
 The protein carried genetic information at the time of
cell division, chromatin change into chromosome.
 The number of chromosomes is constant for particular
species of organism.
 In man there are 23 pair of chromosome present.
 It control nuclear metabolism and cell membrane and
it stored heredity information.

13. 2. Mitochondria
 Mitochondria is a Greek word, it means;
Mito- Thread
Chondria- Granules
 Mitochondria are granules or filamentous of
cytoplasm.
 These are regarded as biochemical machine, which
convert the potential energy of food stuff into kinetic
energy.
 So, they are known as power house of the cell.
 They occur in cytoplasm as variable number. For e.g.
few hundred to few thousand.

14. 2. Mitochondria
 Mitochondria is composed of two layer of membrane
they are;
1. An outer layer which are smooth.
2. An inner layer folded into sheets of tubules called as
‘cristae’.
 Both these layer enclosed a central cavity is known as
‘matrix’.
 Mitochondria is made of phospholipids, protein and
some ribonucleic acid, they also contain some
important enzyme system.
 The energy molecule adenosine tri phosphate (ATP) is
produce in mitochondria.

16. Chemical composition
 Mitochondria consist of protein 73% and lipids 25-
30% of the total lipids, 90% phospholipids and
rest 10% are cholesterol, Vitamin-E and other
inorganic material are present.
 A small of DNA & RNA is also present in
mitochondria.
 These are known as mitochondrial DNA and
mitochondrial RNA.
 50 mitochondria are able to synthesize their own
protein and enzyme.

17. Function of mitochondria
1. Oxidation of food stuff:
 Mitochondria are generally known as power house of the
cell because these brings about oxidation of food stuff.
 They act as power house of cell release energy by the
oxidation of food at the site of cellular respiration.
2. Metabolism of fat:
 The mitochondria said to possess reverse stock of fat
which is needed during germination of seed.
3. Energy conservation:
 During the process of cell division, the ATP play on
important role to convert the potential energy into kinetic
energy.

18. 3. Endoplasmic reticulum
 It is the most extensive cell organelle present in the
cytoplasm.
 Endoplasmic reticulum is a two types they are;
1. Granular endoplasmic reticulum:
 It is also known as rough surfaced endoplasmic reticulum.
 This type of reticulum contains ribosome which are
responsible for protein synthesis.
2. Agranular endoplasmic reticulum:
 It is also known as smooth surface endoplasmic reticulum.
 They do not contain ribosome.
 This type of endoplasmic reticulum is responsible for fatty
acids and steroid synthesis.
 They also stored and release calcium.

20. 4. Golgi apparatus
 It is cup shaped structure which are present in
cytoplasm.
 It is situated between the nucleus and apex of cell.
 Golgi body are double membrane cell organelles,
they are three types;
1. Vesicles
2. Vacuoles
3. Cistern

22. 5. Lysosome
 Lysosome are small spherical or oval shape which
are surrounded by a single membrane.
 They are spherical vesicles that contain hydrolytic
enzymes that can break down many kinds of
biomolecules.
 The damage intracellular organelles are also
broken down and digested by lyposome,
therefore the lyposome are also called as suicide
bag of cell.

24. 6. Centrosomes
 It is a small, rod shaped body found near the
nucleus.
 It play a important role during cell division.
 Centrosomes are made of from arrangement of
two barrel-shaped clusters of microtubules, called
centrioles, and a complex of proteins that help
additional microtubules to form.

26. 7. Microsomes
 They are extremely small membrane, bound
bodies present in cytoplasm.
 Microsome originate from endoplasmic reticulum.
 Microsome contains ribosome and granular matrix,
so they are also responsible for protein synthesize.
 Granular matrix contains enzymes that is;
A. Oxidases- Generate H2O2
B. Catalases- Convert H2O2 into H2O

27. Function of cell
A. Ingestion and assimilation:
 The cell ingests chemical substance like amino acids
from intracellular fluid.
 These substance are used to build up complicated
substance like proteins.
B. Growth and repair:
 The ingested and assimilate materials are use to
synthesize new protoplasm.
 This leads to increase in size and growth of cell.
 Worn out parts of the cell are also replaced by this
process.

28. Function of cell
C. Metabolism:
i. Anabolism:-
 In this process, the ingested and assimilate food
material is used for growth and repair.
ii. Catabolism:-
 In this process, the food material is broken down to
release energy for various function of cell.
D. Respiration:
 It involves transport of oxygen from lungs through
blood to the tissues and removal of waste product
like CO2.

29. Function of cell
E. Excretion:
 The cell eliminates waste products.
 These waste products are carried by blood for
elimination through lungs and kidneys.
F. Irritability and contractility:
 The cell is active by mean of these two function.
 The cell responds to any stimulus (like; physical,
chemical, thermal, electrical and mechanical) by
contracting or the impulse is conducted as that occurs
in nerve cell.

30. Function of cell
G. Selective gate-keeper:
 Cell membrane act as a selective gate-keeper by
functioning as a semi permeable membrane.