Cytoplasm
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5th October 2000
Cytoplasm is the region of the cell between the nucleus and the plasma membrane (outer cell membrane). Its main job is to carry out many metabolic (chemical) processes that sustain the life of the cell and contribute to the larger whole of which the cell is part. Cytoplasm consists mainly of water, electrolytes, carbohydrates, proteins, and lipids (fats), all beautifully arranged and organised. Organelles (‘tiny organs’) are suspended in the cytoplasm. These include ribosomes, endoplasmic reticulum, Golgi apparatus, mitochondria, lysosomes, centrioles, and the cytoskeleton. There are other structures (inclusions) such as melanin granules, fat stores and glycogen stores in specific cell types.
Materials continuously enter and leave the cytoplasm via the plasma and nuclear membranes. Water, electrolytes, energy-rich molecules, amino acids and vitamins enter the cell. Metabolic processes within the cytoplasm result in the formation of materials for export and waste products which are released from the cell. This dynamic balance between inputs and outputs constitutes cellular homeostasis.