Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

6. The Membrane

Active Transport

General Biology

6. The Membrane

Active Transport

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3:48 minutes

Problem 8

Textbook Question

Suppose a cell is placed in a solution with a high concentration of potassium and no sodium. How would the cellular sodium–potassium pump function in this environment?
a. It would stop moving ions across the membrane.
b. It would continue using ATP to pump sodium out of the cell and potassium into the cell.
c. It would move sodium and potassium ions across the membrane, but no ATP would be used.
d. It would reverse the direction of sodium and potassium ions to move them against their gradients.

Verified step by step guidance

Understand the function of the sodium-potassium pump: It is an active transport mechanism that uses ATP to move sodium ions out of the cell and potassium ions into the cell, against their concentration gradients.

Consider the environment described: The solution has a high concentration of potassium and no sodium. This means the external environment is rich in potassium ions but lacks sodium ions.

Analyze how the pump operates: The sodium-potassium pump requires ATP to function, and it typically moves 3 sodium ions out of the cell and 2 potassium ions into the cell per cycle.

Evaluate the impact of the external conditions: Despite the high external potassium concentration, the pump will continue to function as long as ATP is available, because it moves ions against their gradients, not based on external concentrations.

Conclude the pump's behavior: The pump will continue using ATP to transport sodium out of the cell and potassium into the cell, maintaining the cell's internal ion balance, which aligns with option b.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Sodium-Potassium Pump

The sodium-potassium pump is a vital membrane protein that uses ATP to transport sodium ions out of the cell and potassium ions into the cell, maintaining essential concentration gradients. This active transport mechanism is crucial for various cellular functions, including nerve impulse transmission and muscle contraction.

Concentration Gradient

A concentration gradient refers to the difference in the concentration of a substance across a space or a membrane. In cells, gradients are essential for processes like diffusion and active transport, where substances move from areas of high concentration to low concentration, or vice versa, often requiring energy input.

ATP Utilization in Active Transport

ATP (adenosine triphosphate) is the energy currency of the cell, used in active transport to move substances against their concentration gradients. The sodium-potassium pump specifically uses ATP to change its conformation, allowing it to transport sodium and potassium ions across the cell membrane, crucial for maintaining cellular homeostasis.