All organisms are composed of structural and functional units of life called ‘cells’.

The body of some organisms like bacteria, protozoans and some algae is made up

of a single cell whereas the body of higher fungi, plants and animals are composed

of many cells. Human body is built of about one trillion cells.

Cells vary in size and structure as they are specialized to perform different functions.

But the basic components of the cell are common to all biological cells. This lesson

deal...