How does Active Transport work?

Question

I know that it's when protein transporters use energy to transport large or lipid-soluble molecules across a membrane against the concentration gradient, but is it 1), 2), or 3)?

1. More ATP leads to longer service of protein transporters leads to more transport in the end.

2. More protein transporters lead to increased rate of transport.

3. Both 1) and 2).

This is not me cheating. I just don't understand this concept. Please explain it to me in any way you can. Thanks.

Answer 1

3. ATP is used to induce a conformational change in the channel protein's structure. More ATP allows the channel to transport more. 1 channel can only work so fast, even if it is given plenty of stuff to transport. This is called saturation. As long as there is more stuff to transport than the transport can handle, any additional transport proteins will increase the rate at which the stuff crosses the membrane.