Receptor proteins function by which mechanism?

• A. Bind oxygen
• B. Receive and respond to molecular signals
• C. Catalyze reactions
• D. Provide structure

Answer: (B)

Receptor proteins are about sensing signals and turning them into actions inside the cell. They recognize specific chemical messengers—like hormones or neurotransmitters—and binding causes a change in shape or activity. That change starts a signaling cascade inside the cell, often involving second messengers or enzymatic steps, which then alters cellular processes such as gene expression, metabolism, or ion flow. This is why receptor proteins function by receiving signals and initiating a cellular response.

They’re not primarily about binding oxygen—that’s the job of oxygen-carrying proteins like hemoglobin or myoglobin. They’re not mainly enzymes that catalyze chemical reactions, though some receptors can have catalytic roles as part of the signaling pathway. They also don’t provide structural support—that’s the role of structural proteins like collagen or actin.