The movement of substances across membranes using energy from ATP
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What sort of concentrations do substances move from and to?
Low to high
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What in the membrane aids active transport?
Protein pumps
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What are the properties of protein pumps?
Only transport specific substances in a specific direction
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Give an example of where active transport is used in body?
To move sodium and potassium ions into axon membranes of neurons
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These protein pumps in axon membranes are antiporters. What does that mean?
The sodium and potassium ions move in different directions - potassium in, sodium out
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How is the energy acquired for active transport in the axon membranes?
Converting ATP to ADP and phosphate
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What does one ATP provide?
Enough energy to move two potassium ions and three sodium ions
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Why are the concentration gradients generated by active transport needed in the axons?
For the transmission of nerve impulses
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How many binding sites are there in a protein pump for potassium and sodium ions?
Two for potassium, three for sodium
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How does active transport in the axon membrane work?
The pump has two different states: One allows access to binding sites from the outside where there is a stronger attraction for potassium; the other is access to the binding sites from the inside where there is stronger attraction for sodium
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What does the ATP do in active transport of potassium and sodium in axon membranes?
Switch from one state to another and back
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What allows endocytosis and exocytosis to be possible?
The fluidity of the membrane
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State the process of endocytosis
A substance comes into contact with the plasma membrane; part of the membrane is pulled inwards and a droplet of fluid is enclosed when a vesicle is pinched off; Vesicles move through the cytoplasm carrying their contents
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State the process of exocytosis
Vesicles fuse with the plasma membrane; Their contents are expelled; The membrane flattens out again
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State the process of making the proteins to be carried in vesicles in exocytosis
Proteins are made by ribosomes and enter the rough endoplasmic reticulum; Vesicles bud off it and carry the proteins to the golgi apparatus which modifies the proteins; Vesicles bud off the GA and carry the modified proteins to the plasma membrane
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What are vesicles?
Small sacs of membranes used to transport materials from one part of a cell to another
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Does endocytosis use ATP?
Yes
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Give an example of what is taken into the vesicles in endocytosis
Water and solutes from outside the cell; Larger molecules too big to fit through the membrane e.g. antibodies from mother's blood to fetus in placenta; large undigested food particles; pathogens by white blood cells
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Fact card: Sometimes vesicles transport to get inside the vesicle to parts of the cell or proteins of the vesicle membrane
Fact card: Sometimes vesicles transport to get inside the vesicle to parts of the cell or proteins of the vesicle membrane
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How does the area of the plasma membrane get increased?
Phospholipids are made in the rER and are inserted in the rER membrane. Ribosomes off the rER make membrane proteins which insert in the rER membrane. Vesicles bud off the rER and move to the plasma membrane, fusing with it to add phospholipids
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Give examples of what is released by exocytosis
Digestive enzymes from gland cells; The removal of excess water from unicellular organisms
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How are the polypeptides made in digestive enzymes?
They are made in the rER and processed in the GA before being carried to the plasma membrane in vesicles
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What does secretion refer to?
The release of useful substances
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What is another word for vesicle?
Contractile vacuole
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What is another word for 'making'?
Synthesising
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What is the function of an axon?
To convey messages rapidly from one part of the body to another
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What causes the protein pump to change shape when transferring sodium ions?
When ATP transfers a phosphate group to the pump
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What causes the protein pump to change shape when transferring potassium ions?
The release of a phosphate group by the binding of potassium ions
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Other cards in this set
Card 2
Front
What sort of concentrations do substances move from and to?
Back
Low to high
Card 3
Front
What in the membrane aids active transport?
Back
Card 4
Front
What are the properties of protein pumps?
Back
Card 5
Front
Give an example of where active transport is used in body?
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