Which of the following best describes the role of a ligand in cell signaling?

• A. A ligand binds to a receptor to initiate a cellular response.
• B. A ligand is a type of enzyme that catalyzes signal transduction.
• C. A ligand is a structural protein that maintains cell shape.
• D. A ligand acts as a membrane channel for ions.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of cell signaling. Cell signaling is the process by which cells communicate with each other to coordinate various functions. It typically involves a signaling molecule (ligand), a receptor, and a cellular response.
2. Step 2: Define what a ligand is. A ligand is a molecule that binds specifically to a receptor on the surface or inside a cell. This binding triggers a series of events leading to a cellular response.
3. Step 3: Analyze the options provided. Evaluate each statement to determine which one accurately describes the role of a ligand in cell signaling. For example, a ligand is not an enzyme, structural protein, or membrane channel.
4. Step 4: Focus on the correct description. The correct role of a ligand is to bind to a receptor, which initiates a signal transduction pathway resulting in a cellular response.
5. Step 5: Conclude that the correct answer is: 'A ligand binds to a receptor to initiate a cellular response,' as this aligns with the biological function of ligands in cell signaling.