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

8. Membrane Structure

Membrane Proteins

Cell Biology

8. Membrane Structure

Membrane Proteins

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Multiple Choice

What prevents the Na+ and K+ gradients across the plasma membrane from dissipating in animal cells?

The sodium-potassium ATPase pump

Passive diffusion through ion channels

Facilitated diffusion by aquaporins

Endocytosis of ions

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Verified step by step guidance

Understand the role of the sodium-potassium ATPase pump: This is an active transport mechanism that uses ATP to move Na+ and K+ ions against their concentration gradients, maintaining the gradients across the plasma membrane.

Recognize that passive diffusion through ion channels does not prevent dissipation: Ion channels allow ions to move down their concentration gradients, which would lead to dissipation rather than maintenance of the gradients.

Clarify the role of aquaporins: Aquaporins are specialized channels for water transport and do not play a role in maintaining Na+ and K+ gradients.

Understand why endocytosis is not relevant: Endocytosis involves the engulfing of substances into the cell and is not a mechanism for maintaining ion gradients.

Conclude that the sodium-potassium ATPase pump is the correct answer: It actively pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell, using ATP, to maintain the gradients and prevent dissipation.