Materials enter or leave the cells in the following ways:
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Diffusion: It is the movement of substances from the region of the higher concentration to the region of their lower concentration.
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Osmosis: Movement of water molecules from their higher concentration to lower concentration through a semi-permeable membrane.
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Active transport:
(a) Movement of ions and molecules across a membrane against the concentration gradient, i.e. from lower to higher concentration.
(b) It requires energy (ATP).
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Bulk transport:
(a) Transport of large quantities of micro-molecules, macro-molecules and food particles through the membrane.
(b) They are of two types:
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Pinocytosis: Bulk intake of fluid, ions and molecules across the cell membrane by forming small endocytic vesicles of 100-200 nm in diameter. Also called ‘Cell drinking’.
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Phagocytosis: Ingestion of large particles by living cells. Also called ‘Cell eating’.
