Structure of Cell

Cells vary in shape and size. They may be oval, spherical, rectangular, polygonal, spindle shaped, star shaped, rod-shaped or totally irregular like the nerve cell. The diversity in cells is in accordance with the role or function it has to perform as part of the tissue or organ system. In general, there is no typical shape for cells.

 

 

 

 

                

 

Nerve cell                                               Blood cells

 

               

 

Epithelial cells                                  Muscle fibres

The cell, when seen under a light microscope, reveals the following main components:

The cell wall is present only in plant cells. It is made up of a complex polysaccharide (carbohydrate) called cellulose. Its function is to give strength and rigidity to the cell. It is non-living.

Cell membrane is present in both plant and animal cells. It is living, elastic and made of proteins and lipids (fats). Its function is to provide a mechanical barrier for the protection of the inner cell contents and to regulate the movement of molecules in and out of the cell.

The part of the cell between the cell membrane and the nuclear membrane is called the cytoplasm. The cytoplasm consists of the matrix and the organelles. The matrix is a transparent semi fluid substance. When active, it is always in a state of movement. The organelles are found embedded in the cytoplasm. They have definite shape, structure and function. All the metabolic activities of the cell such as synthesis, secretion, digestion and energy generation, are performed by the different cell organelles. Cell organelles can be seen only with the help of an electron microscope.