What is cell

 ANIMAL CELL ;

Animal Cell

*All living bodies are composed of cells.
*But here we will discuss only Animal Cells.

Some main points to be noted are following;

*The body of Animals is composed of trillions of cells.

*The Cell is the basic functional and structural unit of life.

*The single cell contains all the characteristics of life.

*Group of cells are combined and formed TISSUE.

STRUCTURE OF CELL;

The structure of cell is discussed mainly as;

1)Cell Membrane

2)Cytoplasm

3)Nucleus

Now some main points of these parts of cell.

1)CELL MEMBRANE

*Outer protective coverings of cell body is called cell 
membrane.

*Cell membrane mainly membrane composed of mainly three substances

a)Proteins (about 55%) 

b)Lipids (about 40%) 

c)Carbohydrates (about 5%) 

Few models are proposed to describe the structure of cell membrane of the cell
.e.g.,1)Danielli-Davison model
        2)Unit membrane model
        3)Fluid mosaic model

Above the three model Fluid Mosaic Model is accepted till now.This model was proposed by SJ Singer and GL Nichlolson in 1972.

*FLUID MOSAIC MODEL;

According to this model, protein are found to be float in the lipid layer.

 FUNCTIONS OF CELL MEMBRANE;

Main Functions OF CELL Membrane Are Following;

1)Maintenance of size and shape of cells.
2) Cell membrane help to pass some substances and block some substance to pass through it.

3) Gases are exchanged here i.e., oxygen enters the cell from blood 
and carbon dioxide enters in blood from cell

4) Waste products and metabolites are excreted out through cell 
membrane.

5) Nutrients are pass through cell membrane.

6)Protect cytoplasm and Organelles in cytoplasm.

2)CYTOPLASM;

Jelly-like material about 80 is composed of water.
Cytoplasm contains following components;

*Carbohydrates,

*Proteins,

*Lipids,

*Electrolytes,

*Many Organelles.

ORGANELLES IN CYTOPLASM:

There are many organelles in the cytoplasm.

1)Endoplasmic Recticulum;

Network of tubular structure which are interconnected with one another.

*Endoplasmic Recticulum forms a link between nucleus and cell membrane.

*Endoplasmic Recticulum are of two types.

1)Rough endoplasmic recticulum (RER)

2)Smooth endoplasmic recticulum (SER)

*Both are continuous with one another.

*Smooth endoplasmic recticulum changes into rough endoplasmic recticulum and vice versa depending upon activities of cell.

i)Rough endoplasmic Recticulum / (RER)/ (Granular ER)

These are called rough endoplasmic because of their rough and bead like appearance, this rough appearance is due to attachment of granular ribosomes.

Functions;

*RER are mainly Synthesis of those protein which are secreted from the cell e.g., insulin from beta-cell of islets of Langerhans in pancreas.

*RER destroys the worn-out cytoplasmic recticulum.

ii)Smooth Endoplasmic Recticulum (SER)

It is called smooth endoplasmic recticulum because of its smooth surface.

Also called Agranular ER.

Functions;

*It functions is to produce non-protein substance such as cholesterol and steroid.

*Store calcium and release calcium muscle contraction.

*it involves in catabolism and detoxification of toxic substances.