Biology (B3): Osmosis, diffusion and active transport

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What is diffusion?
The process by which particles of a substance spread out from each other, moving from a region where they are in a high concentration to a region of low concentration
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What does diffusion allow for?
Diffusion allows substances to pass into or out of cells across a partially permeable cell membrane.
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In what form must substances be to pass into or out of cells by diffusion?
Dissolved.
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What else must there be present for diffusion to take place?
A concentration gradient must be present between the solutions either side of the cell membrane.
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What is active transport?
Active transport is a transport process which is used to move dissolved molecules from low concentration to high concentration, against a concentration gradient.
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What is the opposite of active transport?
Diffusion.
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What does active transport require to take place?
Energy.
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Where does the energy required for active transport come from primarily?
Respiration.
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How does active transport take place? PART I
Active transport is carried out by a series of protein carriers within the cell membrane. These have a binding site, allowing a specific dissolved substance to bind to the side of the membrane where it is at a lower concentration.
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How does active transport take place? PART II
Energy from respiration then changes the shape of the protein so that it releases the substance onto the other side of the membrane.
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What is an advantage of active transport?
Active transport has the advantage of allowing cells to absorb dissolved substances from very dilute solutions, which is otherwise an impossible process.
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What is a a disadvantage of active transport?
Requires energy (from respiration).
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Give two examples of where active transport takes place.
Root hair cells (plants)- to absorb mineral ions such as nitrates + Small intestine villi cells ( humans) use active transport alongside diffusion to maximise the absorption of glucose and other substances e.g minerals.
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Define osmosis.
The diffusion of water molecules across a partially permeable cell membrane.
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Other cards in this set

Card 2

Front

Diffusion allows substances to pass into or out of cells across a partially permeable cell membrane.

Back

What does diffusion allow for?

Card 3

Front

Dissolved.

Back

Preview of the back of card 3

Card 4

Front

A concentration gradient must be present between the solutions either side of the cell membrane.

Back

Preview of the back of card 4

Card 5

Front

Active transport is a transport process which is used to move dissolved molecules from low concentration to high concentration, against a concentration gradient.

Back

Preview of the back of card 5
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