Table of contents

1. Overview of Cell Biology2h 49m
2. Chemical Components of Cells1h 14m
3. Energy1h 33m
4. DNA, Chromosomes, and Genomes2h 31m
5. DNA to RNA to Protein2h 31m
6. Proteins1h 36m
7. Gene Expression1h 42m
8. Membrane Structure1h 4m
- The Lipid Bilayer
  38m
- Membrane Proteins
  25m
9. Transport Across Membranes1h 52m
10. Anerobic Respiration1h 5m
11. Aerobic Respiration1h 11m
12. Photosynthesis52m
13. Intracellular Protein Transport2h 18m
14. Cell Signaling1h 28m
15. Cytoskeleton and Cell Movement1h 39m
16. Cell Division3h 5m
17. Meiosis and Sexual Reproduction50m
18. Cell Junctions and Tissues48m
19. Stem Cells13m
- Stem Cells
  13m
20. Cancer44m
21. The Immune System1h 6m
22. Techniques in Cell Biology1h 41m

9. Transport Across Membranes

Ion Channels and Membrane Potential

Cell Biology

9. Transport Across Membranes

Ion Channels and Membrane Potential

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Multiple Choice

Why do sodium ions enter a cell when gated sodium channels open?

Because the inside of the cell is positively charged compared to the outside.

Because the sodium ions are actively transported into the cell by the sodium-potassium pump.

Because both the concentration gradient and electrical gradient favor sodium entry into the cell.

Because potassium ions are leaving the cell at the same time.

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Verified step by step guidance

Understand the concept of ion gradients: Sodium ions (Na⁺) are distributed unevenly across the cell membrane. Typically, the concentration of sodium ions is higher outside the cell than inside, creating a concentration gradient.

Learn about the electrical gradient: The inside of the cell is usually negatively charged relative to the outside. This creates an electrical gradient that attracts positively charged ions like sodium into the cell.

Combine the concentration and electrical gradients: Together, these two forces (concentration gradient and electrical gradient) form the electrochemical gradient, which strongly favors the movement of sodium ions into the cell when sodium channels open.

Recognize the role of gated sodium channels: These channels are specific proteins in the cell membrane that open in response to certain signals (e.g., voltage changes or ligand binding), allowing sodium ions to flow into the cell.

Conclude why sodium enters: When gated sodium channels open, sodium ions move into the cell because both the concentration gradient (high to low concentration) and the electrical gradient (negative interior attracting positive ions) favor sodium entry.