A patient is experiencing muscle weakness due to a malfunction in their voltage-gated ion channels. Which of the following best describes the role of these channels in normal cellular function?

• A. Voltage-gated ion channels are always open, allowing ions to freely diffuse across the membrane.
• B. Voltage-gated ion channels use conformational changes to transport ions against their concentration gradient.
• C. Voltage-gated ion channels open and close in response to changes in transmembrane potential, allowing ions to move down their concentration gradient.
• D. Voltage-gated ion channels facilitate active transport by using ATP to move ions against their gradient.

Answer: (C)