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

Light Reactions of Photosynthesis

General Biology

9. Photosynthesis

Light Reactions of Photosynthesis

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1:30 minutes

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

Verified step by step guidance

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.

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.

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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Related Practice

Textbook Question

When light strikes chlorophyll molecules in the reaction-center complex, they lose electrons, which are ultimately replaced by

a. Splitting water

b. Oxidizing NADPH

c. The primary electron acceptor

d. The electron transport chain

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Textbook Question

Which of the following does not occur during the light reactions of photosynthesis?

a. Water is released.

b. Electrons from chlorophyll are moved to a higher-energy state by light.

c. ATP is produced.

d. NADPH is produced to carry electrons to the light-independent reactions.

e. Oxygen is produced when water is split.

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Textbook Question

In mechanism, photophosphorylation is most similar to

a. Substrate-level phosphorylation in glycolysis.

b. Oxidative phosphorylation in cellular respiration.

c. Carbon fixation.

d. Reduction of NADP⁺.

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Textbook Question

Which of the following is a false statement about photosynthesis?

a. During the light-independent reactions, electrons and ATP from the light reactions combine with atmospheric carbon dioxide to produce sugars.

b. The light-independent reactions take place in the chloroplast stroma.

c. Oxygen produced during the light-independent reactions is released into the atmosphere.

d. Chlorophyll absorbs blue and red light and reflects green light.

e. The end product of photosynthesis is a carbohydrate such as glucose.

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Textbook Question

Which of the following correctly identify a role of the ATP produced in the light-capturing reactions? Select True or False for each statement.

T/F It is used by rubisco to fix CO₂ to RuBP.

T/F It serves the same role as ATP produced by mitochondria.

T/F It is used to regenerate RuBP from G3P molecules.

T/F It is used to produce G3P molecules

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Textbook Question

Predict how the following conditions would affect the production of O₂, ATP, and NADPH and state whether noncyclic or cyclic electron flow would occur in each:

(3) blue and red photons hit a chloroplast, but a proton channel has been introduced into the thylakoid membrane, so it is fully permeable to protons.

1024

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Textbook Question

Predict how the following conditions would affect the production of O₂, ATP, and NADPH and state whether noncyclic or cyclic electron flow would occur in each:

(2) blue and red photons hit a chloroplast, but no NADP⁺ is available

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Textbook Question

Predict how the following conditions would affect the production of O2, ATP, and NADPH and state whether noncyclic or cyclic electron flow would occur in each: (1) Only blue photons hit a chloroplast

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