The cell is the basic structural and functional unit of all living organisms and is the smallest unit of life.
A typical cell consists of a cell wall, cell membrane, cytoplasm and nucleus.
A plant cell is surrounded by a cell wall which is made of non-living substances such as cellulose and pectin. The cell wall provides strength and shape to a cell.
Cell membrane, also known as Plasma membrane is made up of Lipids and Proteins and controls the entry and exit of substances.
All the biological activities of a cell are performed by the cytoplasm, a dense liquid inside the cell. The various cell organelles found in the cytoplasm include endoplasmic reticulum, ribosomes, golgi bodies, chloroplasts, mitochondria, lysosomes and vacuoles.
Endoplasmic reticulum in the cytoplasm has ribosomes on its surface which help in protein synthesis. Golgi apparatus helps the cell absorb iron and copper, store fats and secrete hormones in an animal cell. In a plant cell it is known as dictyosome. Chloroplasts known as “the kitchen of the cell”, contain chlorophyll, which help in photosynthesis. Mitochondria are known as the “powerhouse of the cell” as they generate energy for the cell through oxidation of food. Centrioles found in animal or primitive plant cells help in cell division. Lysosomes found in animal cells, contain enzymes and are involved in the digestion of the cell.
The main organelle, that is the Nucleus, generally lies in the centre of the cell and controls all the activities of the cell. It is surrounded by a nuclear membrane. It contains nucleoli and chromosomes. The chromosomes carry DNA which are responsible for transmission of hereditary characteristics. Each living cell has a definite number of chromosomes, with 23 pairs present in each human cell. A cell which has a well developed nucleus is known as a eukaryotic cell. Whereas, a cell with a primitive nucleus is known as a prokaryotic cell.