Question

question 12
the electrochemical gradient across a membrane would generally be increased by which of the following membrane proteins?
o a calcium ion channel
a sucrose-proton cotransporter
a hydrogen ion pump
a sodium ion channel

Explanation:

• Calcium ion channel: Allows calcium ions to flow down their electrochemical gradient (either into or out of the cell depending on the gradient), which would decrease the gradient rather than increase it.
• Sucrose - proton cotransporter: Moves sucrose into the cell along with protons. Protons are moving down their electrochemical gradient (which is used to drive the uptake of sucrose). This does not build up the proton gradient.
• Hydrogen ion pump (proton pump): Actively transports hydrogen ions (protons) against their electrochemical gradient. This builds up the concentration of protons on one side of the membrane and also creates an electrical gradient (since protons are positively charged). So, it increases the electrochemical gradient.
• Sodium ion channel: Allows sodium ions to flow down their electrochemical gradient (either into or out of the cell depending on the gradient), which would decrease the gradient rather than increase it.

Answer:

C. a hydrogen ion pump