The net movement of molecules in a fluid from an area where they are highly concentrated to an area where they are less concentrated.
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What are the factors affecting the rate of diffusion?
Concentration gradient, temperature, surface area of exchange surface, thickness of exchange surface, type of molecule, composition of plasma membrane
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What is facilitated diffusion?
diffusion involving carrier molecules to passively transport molecules across the membrane
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Why use carrier proteins?
Because the diffusion of some molecules across the membrane would be very slow, eg oxygen and gluocse which are needed constantly
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How are the channels selective?
They only open if their specific molecule is present/binds to them, controlling entry and exit to the cell
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Define osmosis.
the movement of water from an area where its water potential is higher to an area where its water potential is more negative across a partially permeable membrane
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What is meant by a high or less negative water potential?
Closer to pure water, high concentration of water and lower concentration of solute
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What is meant by a more negative water potential?
A low concentration of water and a higher concentration of solute
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What happens when a cell has a less negative water potential than the solution its in?
water moves out of the cell and it shrivels
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What happens when the external solution has a less negative water potential than the cell?
Water moves into the cell making it become turgid
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What is meant by plasmolysis?
the shrinkage of the cytoplasm away from the cell wall when a plant cell loses water due to osmosis
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What is meant by an isotonic solution?
A solution that has the same water potential as the cell in it
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What is meant by a hypertonic solution?
A solution that has a more negative water potential than the cell inside it so water moves out of the cell into the solution
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What is meant by a hypotonic solution?
A solution with a less negative water potential than te cell inside it so water moves into the cell
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What is meant by active transport?
The movement of molecules against the concentration gradient that requires energy and carrier proteins
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Explain how active transport works.
Moleucle and ATP both bind to receptor on protein. Phosphorelation occurs, breaking down ATP into ADP and a phosphate molecule. Causes protein to change shape and open channel. Phosphate recombines with ADP to form ATP ready to start again.
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Define co-transport.
The process by which two molecules of different types are simaultaneously transported across a plasma mebrane using carrier proteins
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Other cards in this set
Card 2
Front
What are the factors affecting the rate of diffusion?
Back
Concentration gradient, temperature, surface area of exchange surface, thickness of exchange surface, type of molecule, composition of plasma membrane
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