Active Transport - Biology B3 AQA Watch

AGill07
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Hi,
I'm struggling with active transport in unit 3 biology. What does against the concentration gradient mean? I understand diffusion and osmosis, but I don't really understand what active transport is? It would really help if someone could explain! Thank you
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gapyear2018
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(Original post by AGill07)
Hi,
I'm struggling with active transport in unit 3 biology. What does against the concentration gradient mean? I understand diffusion and osmosis, but I don't really understand what active transport is? It would really help if someone could explain! Thank you

Active transport is the process by which dissolved molecules move across a cell membrane from a lower to a higher concentration. In active transport, particles move against the concentration gradient - and therefore require an input of energy from the cell.

Movement from a lower concentration to a high concentration is moving against the gradient.

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06shawm
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(Original post by AGill07)
Hi,
I'm struggling with active transport in unit 3 biology. What does against the concentration gradient mean? I understand diffusion and osmosis, but I don't really understand what active transport is? It would really help if someone could explain! Thank you
Diffusion is the concept of where you move from a high concentration to a low concentration. This is following a concentration gradient.

Active transport is the opposite. You are moving from a low concentration to a high concentration. Since this process isn't passive it requires energy in the form of ATP which is produced via mitochondria.

Here's an example:

You have a cell membrane. On one side you have abundant sodium ions whereas on the other side of the cell membrane is very little sodium ions. In the case of diffusion, sodium ions are going to passively (i.e doesn't require energy) move via sodium channels across the cell membrane i.e high to low

If you applied the concept of active transport, you would use a transporter to transfer sodium ions from the low concentration side to the high concentration side of the cell membrane. This requires energy i.e ATP produced via mitochondria. This is going against the concentration gradient since you are going from low to high.
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AGill07
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Thank you so much! I understand it now
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AGill07
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But just one quick question; by transporter do you mean the transport proteins?
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06shawm
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(Original post by AGill07)
But just one quick question; by transporter do you mean the transport proteins?
Yes i.e Na+/K+ pump
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AGill07
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Ahhh thank you!
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