Advanced Placement (AP) Biology Practice Exam

Which of the following best defines the process of reception in cell signaling?

1. The release of chemicals into the bloodstream

2. The binding of a signal molecule to a receptor protein

3. The alteration of a protein's function

4. The synthesis of new proteins

The correct answer is: The binding of a signal molecule to a receptor protein

The process of reception in cell signaling is best defined as the binding of a signal molecule to a receptor protein. This crucial first step involves the interaction between a ligand (the signaling molecule) and a specific receptor, which can be located on the cell surface or within the cell. When the signal molecule binds to the receptor, it causes a conformational change in the receptor, initiating a cascade of cellular responses that lead to a physiological effect. This binding is highly specific, meaning that only certain molecules can interact with particular receptors, ensuring that the correct signals are relayed within the cell. The other options describe different aspects of cell signaling but do not specifically define the reception process. The release of chemicals into the bloodstream refers to the broader concept of signal transmission rather than the act of receiving signals. Similarly, the alteration of a protein's function and the synthesis of new proteins describe downstream effects that follow reception but do not encompass the initial binding event that characterizes reception in cell signaling.