Transport across the cell membrane
- Created by: N1ntendo-Sw1tch
- Created on: 25-02-23 19:03
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- Movement Across The Cell Membrane
- Diffusion
- movement of particles/ molecules from an area of high concentration to low
- Passive so no ATP required
- small molecules like oxygen and carbon dioxide and non polar molecules like fatty acids, glycerol and vitamins diffuse directly through
- what affects diffusion rate?
- temp - increases/ decreases particles KE
- concentration gradient - higher gradient the faster
- size- smaller the molecule the faster it diffuses
- thickness - the thicker the membrane the longer it takes
- surface area- large SA = faster diffusion
- graph to show diffusion is a straight increasing line
- Facilitated Diffusion
- The diffusion of substances from a high concentration to low using channel proteins and carrier proteins.
- Passive no ATP required
- Relies on protein channels and carrier proteins
- used by specific molecules e.g. glucose, water (aquaporins), ions ect..
- graph increases then levels off
- levels off because not enough proteins and become saturated
- Methods of facilitated diffusion
- Channel Proteins
- Forms a water filled pore or channel in the membrane
- allows charged substances to diffuse across the membrane e.g. ions
- Carrier Proteins
- have a binding site for a specific solute and constantly flip between two states so that the site is alternately open to opposite ends of the membrane
- e.g. large sugars, amino acids
- co transport (example in epithelial cells)
- molecules move across the membrane with ions
- in epithelial cells glucose moves across the membrane with the Na+ ions through a carrier protein. a protein transports the ions out the cell so theres a concentration gradient so this can happen. the third protein moves the glucose through into the capillary
- Channel Proteins
- Movement of bulk materials
- Exocytosis
- releases large molecules out of the cell. occurs by fusion of the vesicle with the plasma membrane releasing them to the outside
- Endocytosis
- takes large molecules into the cell by creating a vesicle to ingest the molecules and transport them into the cell
- Exocytosis
- Diffusion
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