Please describe overview of cells? (Can write same in exam)

Cells are the basic structural and functional unit of life. They are also known as building blocks of life. There can be various types of cells depending on the criteria selected for classification. On the basis of the presence of a nucleus, it can be classified as prokaryotic and eukaryotic cell. It can also be classified into a plant cell or animal cell. Depending on the function that it performs it can be classified as nerve cell, blood cell, epithelial cell etc.

Different components of cell are as follows:

• Nucleus - responsible for controlling the activity of the cell, as well as cell division
• Endoplasmic reticulum - provides a transport channel within the cell 
• Ribosomes - help in protein synthesis 
• Golgi bodies - help in cell secretion 
• Mitochondria - powerhouse of the cell; liberates energy in the form of ATP
• Vacuoles - store cell sap (mainly found in plant cells)
• Plastids - occur in plant cells; responsible for storing pigments 
• Centrioles - present only in animal cells; help in spindle formation during cell division
• Cell membrane - a semi-permeable membrane that control, cellulose ls the inflow and outflow of substances
• Cell wall - present only in plant cells; non -living, cellulose structure 

Hope this helps.
Regards.