Which of the following is likely to be a response by a receptor protein to an approaching signal molecule?

• A. The receptor protein binds to the signal if it has a complementary shape.
• B. If the signal is able to bind to the receptor it induces a change in the receptor protein's shape.
• C. The change in the receptor protein's shape results in cellular action.
• D. All of the above are correct.

Answer: (D)

Verified step by step guidance

1. Understand that receptor proteins are specific to signal molecules, meaning they have a complementary shape that allows them to bind specifically to certain signals.
2. Recognize that when a signal molecule approaches a receptor protein, the first step is the binding of the signal to the receptor due to their complementary shapes.
3. Once the signal molecule binds to the receptor protein, this binding induces a conformational change in the receptor protein's structure.
4. This change in shape of the receptor protein is crucial as it often triggers a cascade of events inside the cell, leading to a specific cellular response.
5. Conclude that all the statements provided are correct as they describe the sequential process of signal reception and response in cellular communication.