• Cells are the structural and functional units of living organisms. They exhibit all the characteristics of life. They exist as independent unicellular organisms, singly in colonies, and as parts of multicellular organisms. In multicellular organisms, cells become specialized to carry out specific functions. Specialized cells usually cannot live independently.
• A typical cell is made up of protoplasm enclosed within a plasma membrane. A plant cell also has a cellulose cell wall. Protoplasm consists of cytoplasm and a nucleus. The nucleus contains chromatin which are extended chromosomes, structures carrying hereditary information. Cytoplasm contains the following important organelles: mitochondria, chloroplasts, ribosomes, endoplasmic reticulum, Golgi apparatus and Centrioles. each organelle has a specific function.
• Living cells are surrounded by a watery medium. Materials flow between the cell and its environment by diffusion. Osmosis, active transport, and endocytosis or exocytosis.
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