biology 12 - alternative pathways to photosynthesis - section 7-4 and 7-5
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Biology 12 - Alternative Pathways to Photosynthesis - Section 7-4 and 7-5TRANSCRIPT
UNIT A: Cell Biology
Chapter 2: The Molecules of Cells
Chapter 3: Cell Structure and Function
Chapter 4: DNA Structure and Gene Expression
Chapter 5: Metabolism: Energy and Enzymes
Chapter 6: Cellular Respiration
Chapter 7: Photosynthesis:
Sections 7.4, 7.5
In this chapter you will learn how certain pigments, like the ones that give leaves their particular colours, trap energy from the Sun and use it for photosynthesis.
UNIT A Chapter 7: Photosynthesis
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Chapter 7: Photosynthesis
Which pigments provide the maximum efficiency for a plant as it conducts photosynthesis?
Why do leaves appear green in the spring and summer and then turn to red or yellow in the fall?
7.4 Alternative Pathways for PhotosynthesisC3 plants
• mesophyll cells are in parallel layers• bundle sheath cells around plant veins do not contain
chloroplasts
• CO2 is taken up directly by the Calvin cycle
• under high O2 conditions (closed stomata), RuBP carboxylase can bind oxygen instead of CO2 and photorespiration occurs
UNIT A Chapter 7: Photosynthesis Section 7.4
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Figure 7.10a Alternative pathways for photosynthesis.
Figure 7.11a C3 and C4 plant leaf cell arrangement.
C4 Plants
• Mesophyll cells are in concentric rings around bundle sheath cells. CO2 is initially fixed by formation of a 4-carbon molecule, which is transported and then releases CO2 to the Calvin cycle
• When weather is hot and dry and stomata closed, RuBP carboxylase is not exposed to O2 and photorespiration does not occur
UNIT A Chapter 7: Photosynthesis Section 7.4
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C4 Photosynthesis
Figure 7.10b Alternative pathways for photosynthesis.
Figure 7.11b C3 and C4 plant leaf cell arrangement.
CAM plants
• separate components of photosynthesis in time
• CO2 is fixed into a 4-carbon molecule at night (when stomata are open), which releases CO2 for the Calvin cycle in the day
UNIT A Chapter 7: Photosynthesis Section 7.4
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CAM Photosynthesis
Figure 7.10c Alternative pathways for photosynthesis. CAM plants fix CO2 at night, forming a C4 molecule.
UNIT A Section 7.4
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Chapter 7: Photosynthesis
Check Your Progress
1. Identify various plants that use a method of photosynthesis other than C3 photosynthesis.
2. Explain why C4 photosynthesis is advantageous in hot, dry conditions.
UNIT A Section 7.4
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Chapter 7: Photosynthesis
7.5 Photosynthesis Versus Cellular Respiration
UNIT A Chapter 7: Photosynthesis Section 7.5
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Photosynthesis Cellular Respiration
organisms plants, algae, cyanobacteria, not animals
plants, animals, and other organisms
organelle chloroplasts (except bacteria) mitochondria
reactions • metabolic pathway to produce carbohydrate
• uses solar energy• produces ATP by
chemiosmosis
• metabolic pathway to breakdown carbohydrate
• produces ATP by chemiosmosis
UNIT A Section 7.5
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Chapter 7: Photosynthesis
Photosynthesis Versus Cellular Respiration
UNIT A Section 7.5
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Chapter 7: Photosynthesis
Check Your Progress
1. Explain the similarities and differences between cellular respiration and photosynthesis. Use the chemical equations for these reactions in your answer.
2. Explain why a plant cell must contain both chloroplasts and mitochondria.
UNIT A Section 7.5
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Chapter 7: Photosynthesis