Question

Briefly describe the types of cell on basis of shape & size

Answer 1

(1) Surface-volume Ratio:

The cell mem­brane separates the inner content from the outer environment. But this separation does not mean isolation. A number of substances pass in and out through the membrane. These substances are essential for the activities of the cell.

The total surface area of a cell is just sufficient for its inner content. Any increase in the surface area produces manifold increase of the cell volume which upsets the balance. Thus the particular shape and size which a cell attains are determined by the ratio of surface area and inner volume.

(2) Nucleo-cytoplasmic Ratio:

The cell functions by the co-ordinated activities of its different parts. Most important is the co-or­dination between nucleus and cytoplasm. Nucleus produces certain substances which come into the cytoplasm and control its ac­tivities. The cytoplasmic area of a cell is just enough which a nucleus can control.

If the cytoplasmic area is much extended, it will not be possible for the nucleus to control its activity. For this reason a cell never attains size where nucleo-cytoplasmic ratio is more than one-seventh to one-twelfth. In certain cases, this difficulty is overcome by the pres­ence of more than one nucleus in a large cell.

(3) Rate of Cellular Activity:

Though all the cells of a living body are equally impor­tant, yet some cells are metabolically more active than the others. The more active cells are usually smaller and in them, the surface- volume ratio and nucleo-cytoplasmic ratio are in such a level that these cells can work more actively than the larger cells.

(4) Cell Association:

The cell-to-cell at­tachment is important in multicellular forms which render some amount of rigidity. The degree of attachment plays an important role in determining the shape of the cell and their functional property.

It is evident that all the four factors stated above are interrelated and of these the surface-volume ratio and nucleo-cytoplasmic relations play the most important role in de­termining the size, shape and also character­istics of the cell.

But everything depends upon the functions which are to be carried out. In many cells the surface area is increased by various sorts of folding. Such increase has reduced the chance of the alteration of inner volume.

Answer 2

Explanation:

The different types of cell on the basis of their shapes and size are as follows:-

• A 100 cm long nerve cell transmits impulses in the body.
• The sperm cell has a long flagellum that helps it to make it's way to the egg cell.
• The biconcave shape of red blood cell allows them to travel through very narrow blood vessels.
• The spindle shape of muscle cells allows them to contract and relax ,making the muscles move.
• The flat shape of the outer layer of skin cells help them to cover large area.
• White blood cells(WBC) can change their shape.This helps them to engulf germ and digest them.