What allows sodium and potassium ions to flow down their electrochemical gradient across the cell membrane?

• A. Ion channels
• B. Enzymes
• C. Carrier proteins
• D. Receptor proteins

Answer: (A)

Verified step by step guidance

1. Understand the concept of an electrochemical gradient: It is the combination of the concentration gradient and the electrical gradient across a membrane, which influences the movement of ions.
2. Identify the role of ion channels: Ion channels are proteins that create specific pathways for charged ions to pass through the cell membrane.
3. Differentiate between ion channels and other proteins: Ion channels allow ions to flow down their electrochemical gradient without the need for energy, unlike carrier proteins which may require energy to transport substances.
4. Consider the specificity of ion channels: These channels are selective, meaning they allow only specific ions, such as sodium (Na⁺) and potassium (K⁺), to pass through based on size and charge.
5. Recognize the importance of ion channels in maintaining cellular function: The flow of sodium and potassium ions through these channels is crucial for processes such as nerve impulse transmission and muscle contraction.