Transport Across the Plasma Membrane

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Define diffusion.
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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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

Card 3

Front

What is facilitated diffusion?

Back

Preview of the front of card 3

Card 4

Front

Why use carrier proteins?

Back

Preview of the front of card 4

Card 5

Front

How are the channels selective?

Back

Preview of the front of card 5
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