Table of contents
- 1. Introduction to Biology2h 42m
- 2. Chemistry3h 40m
- 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
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses19m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport1h 2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System1h 10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System1h 4m
- 44. Animal Reproduction1h 2m
- 45. Nervous System1h 55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
9. Photosynthesis
Light Reactions of Photosynthesis
Problem 7`
Textbook Question
Which process is most directly driven by light energy?
a. Creation of a pH gradient by pumping protons across the thylakoid membrane
b. Reduction of NADP+ molecules
c. Transfer of energy from pigment molecule to pigment molecule
d. ATP synthesis

1
Understand that the question is about photosynthesis, which is the process plants use to convert light energy into chemical energy.
Identify the role of light energy in photosynthesis. Light energy is primarily absorbed by chlorophyll and other pigments in the chloroplasts.
Recognize that the absorbed light energy excites electrons in the chlorophyll molecules, which is the initial step in the light-dependent reactions of photosynthesis.
Consider each option: (a) involves the creation of a proton gradient, (b) involves the reduction of NADP+, (c) involves the transfer of energy between pigment molecules, and (d) involves ATP synthesis.
Determine that the process most directly driven by light energy is the transfer of energy from pigment molecule to pigment molecule, as this is the immediate result of light absorption, leading to the excitation of electrons.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Photosynthesis
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. It occurs in the chloroplasts and involves two main stages: the light-dependent reactions and the Calvin cycle. Light energy is captured by chlorophyll and other pigments, driving the synthesis of ATP and NADPH, which are used in the Calvin cycle to produce glucose.
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Light-Dependent Reactions
The light-dependent reactions are the first stage of photosynthesis, occurring in the thylakoid membranes of chloroplasts. These reactions require light energy to excite electrons in chlorophyll, leading to the production of ATP and NADPH. The process involves the transfer of energy between pigment molecules and the creation of a proton gradient across the thylakoid membrane, which drives ATP synthesis.
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Energy Transfer in Photosystems
Energy transfer in photosystems involves the movement of energy from one pigment molecule to another within the thylakoid membrane. This process is initiated by the absorption of light energy, which excites electrons in chlorophyll molecules. The energy is then transferred through a series of pigments until it reaches the reaction center, where it is used to drive the light-dependent reactions of photosynthesis.
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