Cell Processes Definitions

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Plasma Membrane

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A phospholipid bi-layer membrane that separates and protects the interior of all cells from the outside environment.

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Active transport

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The movement of molecules across a semi-permeable membrane from a region of lower concentration to a region of higher concentration, requiring energy.

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Diffusion

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The passive movement of particles from a region of higher concentration to a region of lower concentration.

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Facilitated diffusion

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The movement of larger particles from an area of high concentration to an area of low concentration, through protein channels/transport proteins.

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Hypotonic

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A solution with a lower concentration of solutes (or high water potential) compared to another solution, causing cells to swell.

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Isotonic

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A solution with the same concentration of solutes as another solution, resulting in no net movement of water across a cell membrane.

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Osmosis

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The movement of water molecules through a semi-permeable membrane from a region of lower solute concentration (high water potential) to a region of higher solute concentration (low water potential), without the requirement of energy.

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Passive transport

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The movement of substances/molecules across a semi-permeable membrane without the need for energy input.

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Cytosis

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The transport mechanism for the movement of large quantities of molecules into or out of cells.

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Active site

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The region on an enzyme where substrate molecules bind and undergo a chemical reaction.