A cell is the smallest unit that is capable of performing life functions. Major objective of this lecture is to present on Cell Structure. Cell wall, cell membrane, nucleus etc. are part of Cell Structure. Cell wall protects the cell, gives shape and is made of cellulose. Cell membrane are outer covering, protective layer around ALL cells. For cells with cell walls,the cell membrane is inside the cell wall. It allows food, oxygen, & water into the cell & waste products out of the cell. nucleus directs all cell activities and Contains instructions for everything the cell does.