Question

what is the mechanism behind secondary active transport, such as getting sucrose into a cell?
a proton pump is phosphorylated, pumps h+ ions up their concentration gradient, and those ions flow down their concentration gradient coupled with other molecules.
a proton pump pumps h+ ions down their concentration gradient and they then flow up their concentration gradient.
a proton pump pumps h+ ions down their concentration gradient and they flow up their concentration gradient with other molecules.
a proton pump is phosphorylated, pumps h+ ions down their concentration gradient, and those ions flow up their concentration gradient coupled with other molecules.

Explanation:

In secondary active transport, a proton - pump first uses energy (usually from ATP hydrolysis, which phosphorylates the pump) to pump H+ ions against their concentration gradient, creating an electrochemical gradient. Then, the flow of H+ ions down their concentration gradient is coupled with the transport of other molecules (like sucrose) against their concentration gradient.

Answer:

A. A proton pump is phosphorylated, pumps H+ ions up their concentration gradient, and those ions flow down their concentration gradient coupled with other molecules.