biology 12 - plants and carbon dioxide - section 7-3
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Biology 12 - Plants and Carbon dioxide - Section 7-3TRANSCRIPT
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: Section 7.3
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?
7.3 Plants as Carbon Dioxide FixersThe Calvin cycle reactions use atmospheric CO2
to produce carbohydrate. The cycle is divided into three sections:1.Fixation of carbon dioxide: carbon dioxide fixation involves reaction between CO2 and RuBP (a 5-carbon molecule)
• Three CO2 and three RuBP react to produce three 6-carbon molecules; these split forming six 3-carbon molecules (3-phosphoglycerate (3PG))
• ATP is used• RuBP carboxylase catalyzes the reaction; it
is highly abundant in the cell
UNIT A Chapter 7: Photosynthesis Section 7.3
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Calvin Cycle Reactions2. Reduction of carbon dioxide: 3PG is reduced
to G3P and NADPH is oxidized to NADP+
• Each 3PG undergoes reduction to G3P in two steps
• ATP and NADPH are used
UNIT A Chapter 7: Photosynthesis Section 7.3
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3. Regeneration of RuBP: the starting material of the Calvin cycle (RuBP) is replaced.• ATP is used• It takes three turns of the Calvin cycle
for one G3P to exit. For every three turns, five G3P are used to re-form three RuBP and the cycle continues
UNIT A Chapter 7: Photosynthesis Section 7.3
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Calvin Cycle Reactions
UNIT A Chapter 7: Photosynthesis Section 7.3
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Figure 7.9 The Calvin cycle reactions.
The Calvin Cycle
The Importance of the Calvin Cycle
The product of the Calvin cycle, glyceraldehyde-3-phosphate (G3P) can be converted to many other molecules.•Glucose phosphate is made, which is the molecule most often metabolized for energy •Glucose phosphate combines with fructose to produce sucrose, which is used to transport carbohydrates within plants•Glucose phosphate is used for synthesis of starch (storage form of glucose) and cellulose (in cell walls)•G3P is also used for synthesizing fatty acids, glycerol, and amino acids
UNIT A Chapter 7: Photosynthesis Section 7.3
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UNIT A Section 7.3
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Chapter 7: Photosynthesis
Check Your Progress
1. Describe how carbon dioxide is fixed and then reduced to a carbohydrate.
2. Illustrate why it takes three turns of the Calvin cycle to produce one glucose molecule.
3. Explain why G3P is an important molecule in plant metabolism.
UNIT A Section 7.3
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Chapter 7: Photosynthesis