What can the needs of cells not always be met by and why?
Diffusion, because sometimes it may need more of a substance in the cytoplasm than is present on the outside or it may need to move materials in or out more quickly.
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Where are magnesium ions found for plants to intake?
The soil.
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What do plants use magnesium ions for?
To make cholophyll.
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How much of the soil is made up of magnesium ions?
A small amount.
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What must plants do to intake magnesium ions from the soil?
Move them into root hair cells against a concentraion gradient.
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What does active transport do in human bodies?
Absorb glucose from our nutrients.
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What act as pumps for active transport?
Carrier proteins.
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What are carrier proteins similar to?
Carriers used for facilitated diffusion.
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How are carrier proteins shaped?
So the molecules they need to carry fit into them.
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What type of molecules and ions do carrier proteins carry? (2)
Large or charged molecules and ions that can't pass through the lipid bilayer by diffuision. They carry specific molecules 1 way across the membrane.
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What kind of energy do carrier proteins use?
Metabolic energy in the form ATP.
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What direction do carrier proteins carry molecules in terms of concentration gradient?
They carry molecules in the opposite direction to the concentration gradient.
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How quickly do carrier proteins carry molecules across the membrane?
At a faster rate than diffusion.
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Where do molecules accumulate after active transport?
Either inside cells or organelles, or outside cells.
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What does the energy used in pumping molecules across membranes by active transport do to carrier proteins, and what does this do?
It changes the shape of the carrier protein, which means the molecule only fits on 1 side of the membrane.
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What happens as the molecules is carried through the membrane?
It uses energy from ATP which changes its shape so the molecule leaves the carrier protein.
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Why can't molecules go back into the carrier protein after they've been transported?
Because the carrier protein is now a different shape so the molecule won't fit into it.
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What is it called when cells need to move large amounts of molecules in or out?
Endocytosis and exocytosis.
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How is it possible to move large amounts of molecules in or our of cells?
Because membranes can easily fuse, separate and 'pinch off'.
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What does endocytosis and exocytosis require energy wise and why?
Energy in the form of ATP to move the membranes around to form the vesicles that are needed and to move the vesicles around the cell.
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What are the 4 terms used to describe the movements of materials in bulk, and what do they mean?
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