Question

Which of the following statements about Ca2+ pumps is FALSE?

A) It is a form of primary active transport.

B) Calcium is actively transported from the cytosol into the extracellular fluid.

C) Calcium is actively transported from an organelle into the cytosol.

D) The pump is also an ATPase.

E) It maintains low cytosolic calcium levels.

Answer 1

Statement C) is FALSE because Ca2+ pumps actually transport calcium ions into the sarcoplasmic reticulum to lower cytosolic calcium levels, not out of it. This falls under primary active transport where ATP is used, and the Ca2+ pump serves as an ATPase.

Step-by-step explanation:

The student has asked which statement about Ca2+ pumps is FALSE. To address this, let's consider what Ca2+ pumps do. These pumps are involved in primary active transport, where they use ATP to move calcium ions from areas of lower concentration to areas of higher concentration against the electrochemical gradient. Specifically, calcium ions are actively transported into the sarcoplasmic reticulum (an organelle within muscle cells), which helps maintain low cytosolic calcium levels.

Statement C) that calcium is actively transported from an organelle into the cytosol is the FALSE statement, as this is actually the reverse of what happens during muscle relaxation, where calcium ions are actively transported into the sarcoplasmic reticulum, not out of it.