Final answer:
The function of membrane proteins includes transporting molecules across the membrane, cell signaling through receptors, and providing structural support to cells, which means that the correct answer is 4) All of the above.
Step-by-step explanation:
Membrane proteins serve a variety of functions essential to the survival and function of the cell. The function of membrane proteins includes:
- Transporting molecules across the membrane, which could be through means of passive or active transport.
- Acting as receptors for cell signaling, such as receptors for hormones or neurotransmitters.
- Providing structural support to maintain the shape and integrity of the cell.
Therefore, the correct answer to the question would be 4) All of the above.