Exchange Across Plasma Membranes
- Created by: amydowneyjr
- Created on: 23-03-13 14:08
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- Exchange Across Plasma Membranes
- Diffusion
- Passive movement of particles
- Passive means no energy is needed
- From a high to a low concerntration
- Molecules will diffuse both ways but the net movement will always be a low concerntration
- The rate of diffusion depends on many things.
- Concentration gradient - the higher it is, the faster the rate
- Thickness of exchange surface - thinner the exchange surface, shorter the distance there is to travel, faster the rate
- Surface area - larger the surface area (of the membrane) faster the rate
- Passive movement of particles
- Osmosis
- Diffusion of water molecules
- Across a partially permeable membrane
- From a high water potential to a low water potential
- Water potential is basically the same thing as concentration of particles
- Pure water has the highest water potential
- Diffusion of water molecules
- Facilitated Diffusion
- Some larger molecules and charged atoms cant directly diffuse the membrane
- Uses carrier proteins for large molecules
- Large molecule attaches itself to the carrier protein
- Protein changes shape
- This releases the molecule on the opposite side of the membrane
- Protein changes shape
- Large molecule attaches itself to the carrier protein
- Uses Protein channels in the membrane for charged particles
- Protein channels form pores in the membrane for charged particles to diffuse through
- Uses carrier proteins for large molecules
- High to low concerntration
- Passive process
- Some larger molecules and charged atoms cant directly diffuse the membrane
- Active Transport
- Moves against the concentration gradient
- Uses carrier proteins
- Same process as facilitated diffusion
- Except it uses energy from ATP to move the substance against its concentration gradient
- Same process as facilitated diffusion
- Also uses co-transporters
- Type of carrier protein
- Attach two molecules at a time
- The concentration of one of the molecules is used to move the other against its own concentration gradient
- So one molecule is going down its gradient and the other is going against its concentration gradient
- The concentration of one of the molecules is used to move the other against its own concentration gradient
- Diffusion
- The rate of diffusion depends on many things.
- Concentration gradient - the higher it is, the faster the rate
- Thickness of exchange surface - thinner the exchange surface, shorter the distance there is to travel, faster the rate
- Surface area - larger the surface area (of the membrane) faster the rate
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