cell membrane and transport
- Created by: elen roberts
- Created on: 28-04-13 16:21
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- Cell membrane and transport
- Cell membrane
- Phospholipids
- Arranged in a bilayer, different phospholipids have different fatty acids changing the strength and flexibility
- cholesterol links the fatty acids, giving stability and strength
- Proteins
- One side to the other - integral proteins. Sit on the surface - peripheral proteines
- hydrophilic molecules prevent them flipping
- Transport proteins
- Transport of small molecules mostly takes place in integral proteins
- Includes facilitated and active transport
- Receptor proteins
- Outside surface and have a specific binding site
- Binding triggers the event inside the cell
- Recognition proteines
- Cell recognition
- Structural proteines
- Inside surface, attached to cytoskeleton
- Maintain or change cells shape
- Carbohydrates
- Outer surface attached to membrane proteins or phospholipids
- Phospholipids
- Osmosis
- Each solute molecule in a solution attracts a hydrogen shell
- Water potential
- Concentration of free water, pure water is 0, so everything is 0 or <0
- Cells
- Isotonic - equal water potential
- Hypertonic - lower water potential than cell
- Plant cell - cytoplasm shrinks from cell wall (plasmolyses)
- Animal - shrinks (cenerates)
- Hypotonic - lower water potential than cell
- Animal - swells and bursts (lysis)
- Swells and becomes turgid
- Facilitated diffusion
- Channel proteins
- Co-transport. two molecules at one, both must be present
- Substance binds at high concentration and is released at low.
- Carrier proteins
- Water filled pore/channel
- Allows charged substances through
- Gated
- Channel proteins
- Active transport
- Pumping substances through a protein pump up a concentration gradient
- ATP
- Hydrolyse ATP back to ADP + Pand uses the energy to change its shape, allowing substances to pass through
- Synthesised from ADP + phosphate
- Cell membrane
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