CELL

It is structural and functional unit of all living organisms. It is composed of cytoplasm and nuleus enclosed by cell membrane.cell are of different shapes and sizes. It consist of cytoplasm and nucleus.

Structure of an Animal cell:

 Cell membrane:

This is outermost boundary of an animal cell. It is also called plasma membrane.It is composed of lipids and proteins (lipoproteins).A cell membrane is  semi-permeable.

Cell membrane surrounds the cytoplasm and nuleus in all type of cells. In plants and becteria, cell membrane itself is surrounded by a cell wall.

FUNCTION:

It  regulates selective movement of molecules into and out of the cell. It allows certain molecules to pass through it while others can  not pass thought it.

Cell membrane takes in material by infolding in the form of vacuoles. It is called endocytosis.

2: CYTOPLASM:

The protoplasm outside nucleus is called cytoplasm. The cytoplasm exhibits active streaming movements around the inner surface of the cell. This movement is known as cyclosis. It is composed of organic compound such as proteins, carbohydrates, lipids (Fats), enzymes and some inorganic compound e.g water and salts.

Some important cytoplasmic organelles found in eukaryotic cells are as under.

1: Endoplasmic reticulum 2: Golgi complex

3: Mitochondria 4: Plastids (in case of plant cells).

5: Centrioles 6: Ribosomes. 7: Vacuoles.

Function:

It serves as a storehouse of vital chemicals.It is a site of metabolic reactions like protein synthesis, glycolysis etc.Many  reaction can occur at the same time in different regions of the cytoplasm.

3: MITOCHONDRIA: ( Double membrane bounded organells)

They are an important organelle of a eukaryotic cell because they provide energy to the cell and are called the power house of the cell.

Function:

 Mitochondria play an important role in respiration.

They contain enzymes which break down the food for the production of energy.

4: ENDOPLASMIC RETICULUM:

It is a network of channels extending throughout cytoplasm from plasma membrane  to nuclear membrane. They are tube like. They are of two types.

SMOOTH ENDOPLASMIC RETICULUM:

It is nongranular because ribosomes are not attached to it.

ROUGH ENDOPLASMIC RETICULUM:

It is granular as ribosomes in the form of small granules are attached to it.

FUNCTION:

Endoplasmic reticulum plays an important role in the transport of material from one part of the cell to an other.

It is involved in the synthesis of proteins.

It provides mechanical supports to the cell so that its shapes is maintained.

It detoxifies the harmful drugs.

5: NUCLEUS ():

It was discovered by Robert Brown in 1831. It may be spherical or irregular in shape.In animal cell it is usually present in the centre but in plant cell due to the presence of a large vacuole, it is pushed towards the cell membrane.Nucleus is surrounded by a double membrane called the nuclear membrane. Nucleus is filled with a gel like substance called nucleoplasm.

It was discovered by Robert Brown in 1831.It may be spherical or irregular in shape.In animal cell it is usually present in the centre but in plant cell due to the presence of a large vacuole,it is pushed towards the cell membrane. Nucleus is surrounded by a double membrane called the nuclear membrane. Nucleus is filled with a gel like substance called nucleoplasm.