cell-note 1

Cell
1. All living things consist of cell.
2. Our body also is made up of millions of cells.
3. Cells are very small in size. They can only be seen using a microscope.
4. Cells have different shapes and sizes.
5. Cells may be round, oblong, square or of other shapes.
6. Cell is the basic unit of life; its function is to carry out life processes.
7. Generally, every cell is made up of nucleus, cytoplasm and cell membrane.
Structure of cells
Cell membrane – is a thin layer around a cell. It separated a cell from other cells. It controls materials entering and leaving the cells.
Cytoplasm – is a jelly-like fluid in a cell. It is enclosed by the cell membrane. About 70% of cytoplasm consists of water. 30% are protein, starch, mineral salts and vitamins. Many chemical reactions take place in cytoplasm, such as broken down of food to produce energy.
Nucleus – big spherical structure controls all the activities of the cell. It contains genetic materials.
Nucleus and cytoplasm make up protoplasm.
Other cell structures include vacuole, cell wall and chloroplast.
Vacuole – containing cell sap. The cell sap contains dissolved sugar and mineral salts.
Cell wall – surrounding the cell membrane. Made of cellulose and found only in plant cells. Its strong and gives support and protection, also maintains the shape of the cells.
Chloroplasts – containing the green pigment chlorophyll. Its traps sunlight to carry out photosynthesis.
Comparison between plant and animal cell
Animal cell Plant cell
Size Usually small Usually big
Shape Not fixed because no cell wall Fixed shaped because of the cell wall
Cell wall Does not have cell wall Has a cell wall which is made of cellulose
Chloroplasts Does not have chloroplast Has chloroplasts, which contains chlorophyll pigment
Vacuole Does not have or very small Has large vacuole especially in mature cell
Food storage In form of glycogen In form of starch granules
plant cell and animal cell