Question

You have generated antibodies that recognize the extracellular domain of the Ca²⁺-pump. Adding these antibodies to animal cells blocks the active transport of Ca²⁺ from the cytosol into the extracellular environment. What do you expect to observe with respect to intracellular Ca²⁺?

a. Ca²⁺-pumps in vesicle membranes keep cytosolic calcium levels low.
b. Ca²⁺-pumps in the endoplasmic reticulum membrane keep cytosolic calcium levels low.
c. Ca²⁺-pumps in the Golgi apparatus keep cytosolic calcium levels low.
d. Ca²⁺ concentrations in the cytosol increase at a steady rate.

Answer 1

When the antibodies that recognize the extracellular domain of the Ca²⁺-pump are added to animal cells, the active transport of Ca²⁺ from the cytosol into the extracellular environment is blocked, resulting in an increase of intracellular Ca²⁺ concentrations at a steady rate.

Step-by-step explanation:

When the antibodies that recognize the extracellular domain of the Ca²⁺-pump are added to animal cells, the active transport of Ca²⁺ from the cytosol into the extracellular environment is blocked. As a result, the intracellular Ca²⁺ concentrations are expected to increase at a steady rate (choice d). This is because the Ca²⁺ is unable to be actively transported out of the cytosol due to the blocking of the Ca²⁺-pump by the antibodies.