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Chapter Analysis
Intermediate19 pages • EnglishQuick Summary
This chapter on Photosynthesis in Higher Plants focuses on the structure and functioning of the photosynthetic machinery. It explains the process of photosynthesis, which involves converting light energy into chemical energy to synthesize food. The chapter covers the light reactions and carbon fixing reactions, and differentiates between C3 and C4 plants, detailing their pathways and the role of different pigments. The importance of factors such as light, temperature, and water in influencing the rate of photosynthesis is also discussed.
Key Topics
- •Photosystems I and II
- •Electron transport chain
- •Calvin cycle
- •C3 vs C4 pathways
- •Role of chlorophyll and accessory pigments
- •Factors affecting photosynthesis
- •Photorespiration
- •Z-scheme
Learning Objectives
- ✓Understand the process of photosynthesis and its importance.
- ✓Distinguish between C3 and C4 plants and their carbon fixation pathways.
- ✓Comprehend the role of chlorophyll and accessory pigments in capturing light energy.
- ✓Describe the factors that affect the rate of photosynthesis.
- ✓Explain the Calvin cycle and its significance in converting CO2 to sugars.
- ✓Recognize the impact of environmental conditions on photosynthetic efficiency.
Questions in Chapter
By looking at a plant externally, can you tell whether a plant is C3 or C4? Why and how?
Page 151
By looking at which internal structure of a plant, you can tell whether a plant is C3 or C4?
Page 151
Why is the Calvin cycle also called the C3 pathway?
Page 151
Additional Practice Questions
Explain the Z-scheme of electron transport in photosynthesis.
hardAnswer: The Z-scheme describes the movement of electrons through PS II and PS I during the light reactions of photosynthesis. It starts with PS II, which absorbs light leading to electron excitation and release. These electrons are then transferred to PS I through an electron transport chain, generating ATP in the process. PS I absorbs light to further excite these electrons, which then reduce NADP+ to NADPH.
What roles do accessory pigments play in photosynthesis?
mediumAnswer: Accessory pigments, such as chlorophyll b, xanthophylls, and carotenoids, absorb light wavelengths not absorbed by chlorophyll a and transfer the captured light energy to chlorophyll a. This increases the efficiency of photosynthesis by allowing the plant to utilize a broader range of the light spectrum.
Describe the differences between C3 and C4 plants.
mediumAnswer: C3 plants utilize the Calvin cycle for carbon fixation, with the first product being a 3-carbon compound, PGA. They are less efficient under high temperature and light conditions due to photorespiration. C4 plants, however, incorporate CO2 into a 4-carbon compound before entering the Calvin cycle, which minimizes photorespiration and is more efficient in hot, sunny environments. They possess Kranz anatomy to facilitate CO2 concentration around RuBisCO.
How is ATP synthesized in the light reactions of photosynthesis?
mediumAnswer: ATP is synthesized through a process known as photophosphorylation. During electron transport, protons are transferred into the thylakoid lumen, creating a proton gradient. This gradient is used by ATP synthase, which allows protons to flow back into the stroma, driving the conversion of ADP and Pi into ATP.
Why is water important for photosynthesis?
easyAnswer: Water provides the electrons that replace those lost by chlorophyll during light absorption. Its splitting is also linked to the generation of a proton gradient across the thylakoid membrane to aid ATP synthesis, and it releases oxygen as a by-product.