movement of substances across cell surface membrane
- Created by: gbannon334
- Created on: 24-05-18 10:07
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- Movement of Substances across cell surface membrane
- Diffusion across membrane depends on:
- the concentration gradient
- the size of the molecule
- the temperature
- the thickness of the exchange surface
- the SA of the membrane
- Simple Diffusion
- non-polar molecules
- eg. O2 and CO2
- very small
- lipid soluble
- Facilitated diffusion
- when the diffusion process is supported or 'facilitated' by proteins
- two types of protein involved:
- carrier protein- take in the diffusing molecule (eg. glucose), change shape and release the molecule on the other side of the membrane
- (ion) channel proteins- formed by proteins with a central pore that enables charged particles(ions) to pass through. Some are permanently open and some are gated
- Active Transport
- if mols or ions need to be moved across the membrane against the concentration gradient(low to high conc)
- energy in the form of ATP is required
- involves protein carriers (pumps) the substance to be transported binds to the carrier protein
- as with facilitated diffusion, the carrier changes shape and releases transported substance on the other side of the membrane
- two key differences to facilitated diffusion:
- 1) substances are moved against the conc gradient
- 2) metabolic energy in the form of ATP is required
- Diffusion across membrane depends on:
- Active Transport
- if mols or ions need to be moved across the membrane against the concentration gradient(low to high conc)
- energy in the form of ATP is required
- involves protein carriers (pumps) the substance to be transported binds to the carrier protein
- as with facilitated diffusion, the carrier changes shape and releases transported substance on the other side of the membrane
- two key differences to facilitated diffusion:
- 1) substances are moved against the conc gradient
- 2) metabolic energy in the form of ATP is required
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