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

9. Photosynthesis

C3, C4 & CAM Plants

General Biology

9. Photosynthesis

C3, C4 & CAM Plants

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Multiple Choice

Which of the following is an advantage of the C4 pathway over the C3 pathway in plants?

C4 plants are more efficient at fixing carbon dioxide in cool, moist environments.

C4 plants require less ATP per molecule of glucose produced than C3 plants.

C4 plants do not use the enzyme RuBisCO for carbon fixation.

C4 plants have higher photosynthetic efficiency under high light intensity and temperature.

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Verified step by step guidance

Step 1: Understand the difference between the C3 and C4 pathways. The C3 pathway is the most common form of photosynthesis, where carbon dioxide is fixed directly by the enzyme RuBisCO into a 3-carbon compound (3-phosphoglycerate). The C4 pathway, on the other hand, involves an additional step where carbon dioxide is first fixed into a 4-carbon compound (oxaloacetate) by the enzyme PEP carboxylase before being transferred to RuBisCO.

Step 2: Recognize the environmental conditions that favor each pathway. C3 plants are more efficient in cool, moist environments with moderate light intensity, while C4 plants are adapted to high light intensity, high temperatures, and dry conditions. This adaptation allows C4 plants to minimize photorespiration, which is a wasteful process that occurs in C3 plants under these conditions.

Step 3: Analyze the role of RuBisCO in both pathways. RuBisCO is used in both C3 and C4 plants for carbon fixation during the Calvin cycle. However, C4 plants use PEP carboxylase in the initial step of carbon fixation, which has a higher affinity for carbon dioxide and is not affected by oxygen levels, reducing photorespiration.

Step 4: Evaluate the energy requirements of the C4 pathway. While the C4 pathway requires more ATP than the C3 pathway due to the additional steps involved, this energy cost is offset by the higher photosynthetic efficiency under high light intensity and temperature conditions.

Step 5: Conclude that the advantage of the C4 pathway over the C3 pathway is its higher photosynthetic efficiency under high light intensity and temperature, making it better suited for plants in hot and dry environments.