Exchange Across Cell Membranes
- Created by: Narey7Emily97
- Created on: 09-12-13 14:15
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- Exchange Across Cell Membranes
- Diffusion
- Diffusion is the net movement of particles (molecules or ions) from an area of higher concentration to an area of lower concentration
- Molecules will diffuse both ways but the net movement will be to the area of lower concentration. This continues until particles are evenly distributed thorough the liquid of gas
- The concentration gradient is the path from an areas of high concentration to an area of lower concentration. Particles diffuse down a concentration gradient
- Diffusion is a passive process - no energy is needed for it to happen
- Particles can diffuse across cell membranes as long as they can move freely through the membrane
- The rate of diffusion depends on several factors
- The concentration gradient - the higher it is the faster the rate of diffusion
- The thickness of the exchange surface - the thinner the exchange surface the faster the rate of diffusion
- The surface area - the larger the surface area the faster the rate of diffusion
- Facilitated Diffusion
- Carrier proteins move large molecules into or out of the cell, down their concentration gradient. Different carrier proteins facilitate diffusion of different molecules
- First, a large molecule attaches to a carrier protein in the membrane
- Then the protein changes shape
- This releases the molecyle on the opposite side of the membrane
- Then the protein changes shape
- First, a large molecule attaches to a carrier protein in the membrane
- Channel proteins from pores in the membrane for charged particles to diffuse through. Different channel proteins facilitate the diffusion of different charged particles
- Carrier proteins move large molecules into or out of the cell, down their concentration gradient. Different carrier proteins facilitate diffusion of different molecules
- Diffusion is the net movement of particles (molecules or ions) from an area of higher concentration to an area of lower concentration
- Osmosis
- Osmosis is Diffusion of water molecules
- Osmosis is the diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential
- Water potential is the potential of water molecules to diffuse out of or into a solution
- Pure water has the highest water potential of zero. All solutions have a lower water potential than pure water
- Water potential is the potential of water molecules to diffuse out of or into a solution
- Active transport
- Active transport uses energy to move molecules and ions across plasma membranes, against a concentration gradient
- Carrier proteins are involved in active transport
- A molecule attaches to the carrier protein, the protein changes shape and this moves the molecule across the membrane, releasing it on the other side
- Co-transporter are a type of carrier protein
- They bind two molecules at a time
- The concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient
- They bind two molecules at a time
- Diffusion
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