Cells are the building blocks of all living things, either

unicellular or multicellular. All metabolic activities are

performed within cells. Metabolism, excretion,

reproduction, respiration, irritability and growth are the

basic functions that cells must perform.

Cells have vital roles in the survival of an organism

despite their differences in structure and function. All are

involved in different functions such as movement, support,

energy etc. Thus, the unity of an organism is maintained by

differentiated cells. Although cells differ in function and

shape, they all possess an almost identical structure.

All are composed of a plasma membrane (or cell

membrane), cytoplasm and nucleus. The plasma

membrane is involved in the protection of the cell, providing

shape, transport of materials and communication.

In plant cells, the plasma membrane is surrounded by a

rigid cell wall. It is nonliving and is composed of cellulose

molecules. Gates in the cell wall allow the passage of

The cell wall provides shape for the plant cell and protects it

against hazards.

The cytoplasm is the liquid portion of the cell located between

the plasma membrane and the nucleus. It is composed of

organelles, organic and inorganic molecules. The organic

molecules of the cytoplasm are carbohydrates, proteins, fats and

nucleic acids. The inorganic molecules are minerals, water, etc.

The organelles of the cytoplasm are endoplasmic reticulum, Golgi

apparatus, ribosomes etc.

The nucleus is the most vital component of the cell. It contains

coded genetic information within its chromosomes. The cell can

not survive if it is removed.