Draw and label the plasma membrane of a cell that is placed in a solution with concentrations of calcium ions and lactose that are greater than those on the inside of the cell. Use arrows to show the relevant gradients and the activity of the following membrane proteins: (1) a pump that exports protons; (2) a calcium channel; and (3) a lactose carrier.

Verified step by step guidance

1. Draw the phospholipid bilayer of the plasma membrane, showing the hydrophilic heads facing outward and the hydrophobic tails facing inward.
2. Label the extracellular space and the intracellular space (cytoplasm).
3. Draw and label the proton pump, showing it actively exporting protons (H+) from the intracellular space to the extracellular space using ATP.
4. Draw and label the calcium channel, showing calcium ions (Ca2+) moving passively from the extracellular space to the intracellular space down their concentration gradient.
5. Draw and label the lactose carrier, showing lactose molecules moving from the extracellular space to the intracellular space, possibly through facilitated diffusion.