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

Introduction to Photosynthesis

General Biology

9. Photosynthesis

Introduction to Photosynthesis

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Multiple Choice

Why is it difficult to determine the optimal concentration of CO$_2$ for photosynthesis when light intensity is very low?

Because CO$_2$ is not required for photosynthesis at low light intensities.

Because low light intensity increases the rate of photorespiration instead of photosynthesis.

Because low light intensity limits the rate of photosynthesis regardless of CO$_2$ concentration.

Because high CO$_2$ levels inhibit chlorophyll production at low light.

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Verified step by step guidance

Understand the relationship between light intensity and photosynthesis: Photosynthesis is a light-dependent process, meaning that light energy is required to drive the reactions that convert CO$_2$ and water into glucose and oxygen. At very low light intensities, the energy available for photosynthesis is limited.

Recognize the role of CO$_2$ in photosynthesis: CO$_2$ is a substrate for the Calvin cycle, which occurs during the light-independent reactions of photosynthesis. However, the Calvin cycle relies on ATP and NADPH produced during the light-dependent reactions, which are constrained by low light intensity.

Analyze why CO$_2$ concentration has limited impact at low light: Even if CO$_2$ levels are increased, the rate of photosynthesis cannot significantly improve because the light-dependent reactions are the bottleneck. Without sufficient light, ATP and NADPH production is insufficient to support the Calvin cycle.

Clarify why other options are incorrect: CO$_2$ is always required for photosynthesis, even at low light intensities. Low light intensity does not increase photorespiration; instead, it limits photosynthesis overall. High CO$_2$ levels do not inhibit chlorophyll production; chlorophyll production is regulated by other factors.

Conclude that the correct answer is based on the limiting factor principle: At low light intensities, light availability is the primary limiting factor for photosynthesis, regardless of CO$_2$ concentration.