Which of the following statements is true of both membrane potential responses shown in the graphs?

• A. Both responses are initiated by the passive diffusion of glucose across the membrane.
• B. Both responses involve a rapid depolarization followed by a repolarization phase.
• C. Both responses result in the membrane potential remaining above 0 mV for an extended period.
• D. Both responses require the direct input of ATP to open voltage-gated sodium channels.

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by understanding the concept of membrane potential. Membrane potential refers to the difference in electrical charge across a cell's membrane, which is primarily influenced by the movement of ions such as sodium (Na⁺), potassium (K⁺), and chloride (Cl⁻). This movement is regulated by ion channels and pumps.
2. Step 2: Analyze the options provided in the problem. Each statement describes a potential characteristic of the membrane potential responses shown in the graphs. Carefully evaluate each statement based on biological principles and mechanisms.
3. Step 3: Consider the role of passive diffusion of glucose. Glucose transport across the membrane typically occurs via facilitated diffusion or active transport, not passive diffusion. Additionally, glucose transport does not directly initiate changes in membrane potential, as membrane potential is primarily influenced by ion movement.
4. Step 4: Examine the concept of depolarization and repolarization. Depolarization refers to the rapid increase in membrane potential (becoming less negative), often due to the influx of Na⁺ ions. Repolarization is the process of returning the membrane potential to its resting state, often involving the efflux of K⁺ ions. This pattern is common in action potentials.
5. Step 5: Evaluate the role of ATP in opening voltage-gated sodium channels. Voltage-gated sodium channels open in response to changes in membrane potential, not directly due to ATP input. ATP is typically used by ion pumps, such as the sodium-potassium pump, to maintain ion gradients across the membrane.