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Transport (Factors affecting diffusion (Tempterature (More kinetic energy…
Transport
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Keywords
Osmosis: Passage of water molecules down the water potential gradient across a partially permeable membrane
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Active transport: Movement of substances from an area of low concentration to an area of high concentration (against the concentration gradient) across a cell membrane using ATP and protein carriers
Endocytosis: Bulk transport of molecules, too large to pass through the cell membrane even via channel or carrier proteins, into the cell
Segment of plasma membrane surrounds and encloses the particle and brings it into the cell, enclosed in a vesicle
Exocytosis: Bulk transport of molecules too large to pass through the cell membrane even via carrier or channel proteins out of the cell
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Osmosis
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Turgid: Plant cell swells and the cell contents presses up against the cell wall due to an increase in water but the cell wall prevents bursting
Plasmolysed: Cytoplasm of plant cell shrinks and the membrane pulls away from the cell wall due to a lack of water
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Facilitated diffusion
Passive movement of molecules from an area of high concentration to an area of low concentration across a partially permeable membrane via protein channels or carriers
Polar molecules cannot interact with the hydrophobic tails of the lipid bilayer so diffuse through water-filled protein channels around 0.8nm in diameter
Cholesterol within the membrane reduces the permeability of large molecules through the membrane so these also diffuse through a water-filled protein channel. They can also bind to transmembrane carrier proteins, allowing the molecules to diffuse to the other side
Carrier proteins
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The energy helps the carrier protein change its conformation and carries the molecule/ion from one side of the cell membrane to the other
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Simple diffusion
Movement of molecules from an area of high concentration to an area of low concentration, not requiring ATP energy
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