passive net movement of molecules from an area of high to low concentration, down the concentration gradient
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How can the rate of diffusion be maximised?
large SA, large difference in concentration, short diffusion pathway
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What is Osmosis?
passive net movement of water molecules(or water soluble molecules) from an area of high water potential to low water water potential
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What does 'water potential' mean?
the ability for water to leave a solution
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What is the water potential of pure water?
0
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What is Osmolarity measured in?
Osmoles of a solute per litre of solution
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What is a Hypertonic solution?
Higher solute concentration (less water) than other solution
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What is a hypotonic solution?
Lower solute concentration (more water) than other solution
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What is an isotonic solution?
The same salt concentration as the cell/blood
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What is facilitated diffusion?
proteins in the phospholipid bilayer help to transport molecules that are charged/can't fit through alone
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How do Channel proteins perform facilitated diffusion?
they are ion gated channels filled with water, to transport charged
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How do Carrier proteins perform facilitated diffusion?
the molecule binds to the protein, causing a conformational shape change which releases the molecule on the other side
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How does co-transport work?
The carrier proteins transports 2 molecules at the same time, one goes against the concentration gradient (and is dragged by the other one, going in the 'right' direction)
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What is Active transport?
Protein pumps use energy/ATP to transport substances against the concentration gradient
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What is Kidney dialysis?
Mimics function of the human kidneys using various concentration gradients. 'dirty' blood runs along side dialysis fluid, and is returned when it is 'clean' (with correct ion/water, glucose levels and no urea)
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What is dialysis fluid?
Contains no urea, contains water/ion and glucose level found in normal blood (so urea diffuses out)
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Why does Kidney dialysis use countercurrent flow?
to maximise the difference in concentration gradient, for quicker diffusion
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What is Exocytosis?
molecules to be expelled are contained in membrane vesicles, which travels towards the membrane, then fuse with it to expel the molecules
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What is Endocytosis?
molecules are closed by a fold in the membrane which pinches off (invagination), materials are then ingested and absorbed
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Why does the fluidity of the membrane allow endo/exocytosis?
The hydrophobic and hydrophilic parts of the phospholipid tails are weakly associated, so can be pinched off, allowing molecules to pass through
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What type of protein is an Na/k pump?
Integral protein pump
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What happens first (with Na) in Na/K pump?
3 sodium ions bind to it, then a phosphate group (via ATP) is transferred to it, causing a conformational shape change (releasing na
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What happens next (with K) in the Na/K pump?
The conformational shape change exposes 2 K binding sites, the Phosphate group is released, causing conformational shape change which returns the pump back to its original shape
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Other cards in this set
Card 2
Front
How can the rate of diffusion be maximised?
Back
large SA, large difference in concentration, short diffusion pathway
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