All organisms are composed of one or more cells. The cell is the basic unit of organisation of organisms. All cells come from pre-existing cells. Both animal cells and plant cells have a cell membrane surrounding the cytoplasm. Both animal cells and plants cells have a nucleus. Both animal cells and plant cells contain mitochondria. In animal cells, it is relatively smaller in size and irregularly shaped. The vacuole in animal cell is small or absent and its nucleus is at the centre. Animal cells use glycogen granules as food storage and is without chloroplast. Plant cells are relatively larger in size and regular shaped. Plant cells have large central vacuole and its nucleus is near the cell wall.

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Cell membrane is thin and elastic and his tiny pores. The cell membrane is selectively permeable and controls the movement of substances into and out of a cell. Cytoplasm is jelly-like and contains mainly water and small structures called organelles. Cytoplasm is where most chemical reactions take place. Nucleus is the largest organelle in the cell and controls the activities of the cell. The mitochondrion is involved in the release of energy in respiration. The cell wall is found outside the cell membrane. The cell wall is thick and tough and made of cellulose. The cell wall contains large holes and is freely permeable. The cell wall keeps the shape of the cell and protects inner structures. The vacuole is a large, central space filled with cell sap and is a storage of various substances. Chloroplast contains green pigment called chlorophyll and absorbs light energy in photosynthesis for making food. Ribosome are tiny structures in the cytoplasm and site of protein synthesis.