Question

Which of the following proteins in a plant cell transports substances or conducts signals across the plasma membrane?
Select all that apply.

ribosome
aquaporin
proton pump
calcium channel
ATP synthase

Answer 1

In a plant cell, the following proteins transport substances or conduct signals across the plasma membrane:

1. **Aquaporin** - This protein facilitates the transport of water across the plasma membrane.

2. **Proton pump** - This actively transports protons (H+ ions) across the membrane, creating a gradient that can be used for various cellular processes, including nutrient uptake.

3. **Calcium channel** - This protein allows the passage of calcium ions (Ca²+) across the plasma membrane, which is important for signaling processes.

**ATP synthase** is primarily located in the thylakoid membrane of chloroplasts and the inner mitochondrial membrane (not directly in the plasma membrane), so it does not fit the description of transporting substances across the plasma membrane.

**Ribosome** is not involved in transporting substances; instead, it is a molecular machine that synthesizes proteins.

Thus, the proteins that transport substances or conduct signals across the plasma membrane are:

- Aquaporin
- Proton pump
- Calcium channel