Transport across the Membrane
- Created by: penny.ee
- Created on: 26-04-17 13:49
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- Membrane Transport
- Phospholipid Bilayer
- Fluid Mosaic - as phospholipids are able to move laterally to one another/swap places. Mosaic refers to the arrangement of phospholipids and proteins
- consists of a bilayer of hydrophobic fatty acid tail and hydrophyllic phosphate head
- includes; intrinsic/ extrinsic proteins, peripheral protein etc.
- Simple Diffusion
- The passive, net movement of molecules/ ions from an area of high con. to low con. until they are evenly distributed
- Factors Affecting
- Temperature: as temp. increases, so does the amount of kinetic energy = faster diffusion rate
- Conc. Gradient: The greater the difference on either side of the diffusion pathway, the greater the rate
- Surface Area: larger surface area = faster rate
- Diffusion pathway: short = faster rate
- Facilitated Diffusion
- Carrier Proteins
- 1) Molecules bind to binding sites within the protein from the area of high conc.
- 2) Molecules are then released across the membrane from the binding sites
- Channel Proteins
- Transport small, polar molecules e.g. ions
- The channel pore is charged to guide the ions (each channel is specific to the ion)
- Carrier Proteins
- Active Transport
- The active, net movement of molecules/ ions into/out of a cell against a concentration gradient
- The process requires ATP and is used in: protein synthesis, muscle contraction, neurotrans-missions and mineral absorption
- It uses carrier proteins with specific binding sites and only take complement-ary molecules
- CO TRANSPORT - an indirect form of active transport e.g. Sodium/ Potassium pump
- Actively transports Na+ out of the blood and K+ into the cell
- The carrier protein transports glucose down the conc. gradient
- The co-transport protein transports Na+ down the conc. gradient and glucose against the conc. gradient
- CO TRANSPORT - an indirect form of active transport e.g. Sodium/ Potassium pump
- Osmosis
- Passage of water from a solution of high water potential to a solution of low water potential through a partially permeable membrane
- HYPERtonic
- Water potential is lower on the outside
- Water leaves the cell and becomes flaccid
- Pressure falls
- HYPOtonic
- Water potential is higher outside
- Water enters the cell and becomes turgid
- Pressure rises
- Low WP = more negative (less free water molecules = conc. solution)
- Isotonic Solution - if solution has the same water potential both in and out of the cell
- Water Potential - the pressure created by the water molecules trying to diffuse out of a solution down a gradient
- Phospholipid Bilayer
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