How does food from the gut lumen reach the capillaries in the gut wall?
Food molecules cross the plasma membrane of the epithelial cells of the small intestine. This is folded into mircovilli. Then crosses another plasma membrane closer to the capillaries.
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Components of a plasma membrane?
Lipids (mainly phospholipids) proteins and carbohydrates (attached to the proteins or lipids)
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Why is the plasma membrane seen as the fluid mosaic model?
Because in the model phospholipid molecules for a continuous double layer (bilayer). These phospholipds are constantly moving making it a fluid. The scattered protein molecules throughout the layer are like tiles in a mosaic.
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Triglycerides
A type of lipid. One molecule of glycerol and 3 fatty acids attached to it. Fatty acid molecules have long chains of hydrocarbons making lipids insoluble in water. Fatty acids are joined to the glycerol by condensation reaction.
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Two kinds of fatty acids?
Saturated and unsaturate. The difference is their hydrocarbon tails. Saturated fatty acids have no double bonds between carbon atoms, where as unsaturated fatty acids do have double bonds casuing the chain to 'kink'
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Phospholipids
Very similar to triglycerides but one molecule of faty acid is replaced by a phosphate group. This is hydrophilic where as the fatty acidsare hydrophobic.
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How to test for lipids?
EMULSION TEST. Shake the substance with ethanol then pout into water, if lipids are present they will show up as a milky emulsion.
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Diffusion
Net movement of particles from an area of high conc to area of low conc. It is a passive process so no energy is required. Some particles can simply diffuse across plasma membranes.
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Factors of Rate of Diffusion
-Concentration gradient -Thickness of exchange surface -Surface area
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Osmosis
Diffusion of water molecules across a partially permeable membrane from high water potential to a low water potential. Plasma membranes are partial permeable so large molecules cant easily pass through but water can.
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Isotonic
When two solutions have the same water potential
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Carrier Proteins
One type of faciliated diffusion. They move large molecules into or out of the cell down the conc gradient. Different proteins faciliate the diffusion of diff molecules. When a molecule is attached the protein changes shape and releases other side.
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Channel ProteinsDiff
Different way of faciliated diffusion. Have a hole or a pore running through the centre. Diffuse charged particles (ions) into or out of the plasma membrane. Different proteins diffuse different ions. Some channels can be opened and closed by stimuli
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Active Transport
Substances are moved against a concentration gradient. Sodium potassium pump is used to actively transport sodium ions into a cell. Works by taking three ions out while only two go in. Uses energy in the form of ATP.
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Other cards in this set
Card 2
Front
Components of a plasma membrane?
Back
Lipids (mainly phospholipids) proteins and carbohydrates (attached to the proteins or lipids)
Card 3
Front
Why is the plasma membrane seen as the fluid mosaic model?
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