Crossing membranes - Active transport

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  • Created by: Steff06
  • Created on: 06-04-16 11:42
Define active transport
Movement of molecules or ions across membranes, which uses ATP to drive protein pumps within the membrane.
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How is active transport different to simple diffusion?
Active transport is against a concentration gradient via carrier proteins.
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Why may active transport be used instead of diffusion?
Sometimes cells may need to move material into or out of a cell more quickly than diffusion allows.
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How do these protein pumps differ from the proteins used in facilitated diffusion?
Carry molecules in opposite direction to conc gradient. Carry molecules at a faster rate than diffuse. Molecules accumulate inside or outside cells. Carry molecules 1 way across the membrane. Carry them using energy (ATP).
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How is 1 way flow ensured?
Energy used to pump molecules across membranes by active transport changes the shape of carrier protein so the specific molecule fits into the carrier protein on one side of the membrane only. Carrier uses ATP which changes shape of carrier protein.
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What does this changed shaped mean?
The molecule cannot enter the transport protein, because the protein is now a different shape so it will not fit.
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Give an example of active transport in muscles
Calcium ion movement in muscles
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Explain calcium ion active transport in muscles
Muscle fibres only fibres when calcium ions are present. When muscles are stimulated to contract, Ca+ ions released. When muscle needs to relax, Ca+ ions pumped back into stores.
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Decsribe endocytosis and exocytosis in bulk transport
Endocytosis = Bringing materials into the cell. Exocytosis = Moving materials out of the cell.
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What does bulk transport require and what is it required for?
Requires ATP to move membranes around to form vesicles needed and to move these around the cell.
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Give examples of bulk transport
Hormones e.g. insulin. Plant cells e.g. materials to build cell wall. White blood cells (engulf microorganisms by forming vesicles).
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Card 2

Front

How is active transport different to simple diffusion?

Back

Active transport is against a concentration gradient via carrier proteins.

Card 3

Front

Why may active transport be used instead of diffusion?

Back

Preview of the front of card 3

Card 4

Front

How do these protein pumps differ from the proteins used in facilitated diffusion?

Back

Preview of the front of card 4

Card 5

Front

How is 1 way flow ensured?

Back

Preview of the front of card 5
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