Which statement best describes cell membrane receptors?

Which statement best describes cell membrane receptors?

• A. Extracellular fluid
• B. Nucleus
• C. Cell membrane receptors
• D. Tissues

Answer: (C)

Cell membrane receptors are specialized proteins embedded in the cell’s outer membrane that detect chemical signals outside the cell. When a specific signaling molecule, or ligand, binds to its receptor, the receptor changes shape and triggers internal signaling pathways, often involving second messengers or kinase cascades, to bring about a cellular response. This makes the option describing receptors themselves the best fit because it directly refers to what these signaling proteins are. The other choices point to entities that play different roles: extracellular fluid is the environment outside the cell, the nucleus is the cell’s genetic control center inside, and tissues are groups of cells forming structures. Receptors are the mechanism by which cells perceive and respond to external signals.

Cell membrane receptors are specialized proteins embedded in the cell’s outer membrane that detect chemical signals outside the cell. When a specific signaling molecule, or ligand, binds to its receptor, the receptor changes shape and triggers internal signaling pathways, often involving second messengers or kinase cascades, to bring about a cellular response.

This makes the option describing receptors themselves the best fit because it directly refers to what these signaling proteins are. The other choices point to entities that play different roles: extracellular fluid is the environment outside the cell, the nucleus is the cell’s genetic control center inside, and tissues are groups of cells forming structures. Receptors are the mechanism by which cells perceive and respond to external signals.