Question

comparing the calcium and sodium-potassium pumps
which statement describes a similarity between the calcium pump and the sodium-potassium pump?
○ both pumps move substances from high concentration to low concentration.
○ both pumps only move substances into cells.
○ both pumps require no energy to function.
○ both pumps use proteins to transport substances across the cell membrane.

Explanation:

1. Analyze Option 1: Both calcium and sodium - potassium pumps are active transport mechanisms, which move substances from low to high concentration, not high to low. So this option is incorrect.
2. Analyze Option 2: The sodium - potassium pump moves sodium out of the cell and potassium into the cell, and the calcium pump can move calcium out of the cell (e.g., in muscle cells). So they don't only move substances into cells. This option is incorrect.
3. Analyze Option 3: Active transport pumps like these require energy (usually from ATP) to function. So this option is incorrect.
4. Analyze Option 4: Both the calcium pump and the sodium - potassium pump are types of membrane transport proteins. They use these proteins to transport substances across the cell membrane. This statement is correct.

Answer:

D. Both pumps use proteins to transport substances across the cell membrane.