Bio122 Fall 2015 Lecture 3: Energy Acquisition - Outline & Study Questions
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Lecture Outline:
I. Energy Acquisition
A. Energy sources
B. Obtaining Energy: Autotrophy
1. Chemosynthesis
2. Photosynthesis (C3 pathway)
a. Light reaction
i. Capture photon
ii. Use energy from photon to split water
iii. Use electron from splitting water to synthesize ATP & NADPH
b. Calvin cycle
i. Uptake of CO2
ii. Synthesis of 3-C compound (PGA)
iii. Synthesis of 6-C compound (glucose)
C. Photosynthesis constraints & solutions
1. Light
2. Temperature
a. rubisco – catalyst for 2 competing reactions
b. C4 photosynthesis (spatial separation of cycles)
i. Light reaction the mesophyll – 4-C compound created
ii. 4-C to bundle sheath, providing CO2 & 3-C compound for glucose
synthesis
c. C3 vs. C4 photosynthesis
3. Water
a. CAM photosynthesis (temporal separation of cycles)
4. Nutrients
Study Questions:
1. Define: chemical energy; autotrophy; heterotrophy; chemosynthesis; photosynthesis;
oxidize; pigment; chlorophyll; chloroplasts; stomates; cellular respiration;
photorespiration; mesophyll; bundle sheath; PEPcase
2. What types of organisms are chemosynthetic?
3. Write the basic, overall equation for photosynthesis.
4. List the 2 stages of photosynthesis. For each stage, list the inputs and outputs.
5. What is the role of rubisco & which photosynthetic pathway is it active in?
6. Why is the typical form of photosynthesis referred to as C3 photosynthesis?
7. List 4 factors that constrain photosynthesis.
8. Draw a basic light response curve and explain what it means.
9. List 4 ways that a plant can acclimatize to light variation and thus increase the efficiency
of photosynthesis.
10. Rubisco can catalyze 2 competing reactions – what are they and what do they mean for
a plant?
11. List and briefly describe 2 ways in which high temperatures reduce the efficiency of
photosynthesis.
Bio122 Fall 2015 Lecture 3: Energy Acquisition - Outline & Study Questions
12. In what way does C4 photosynthesis overcome the challenges presented by high
temperatures?
13. Why is PEPcase a more efficient enzyme than rubisco for the light reaction of C4
photosynthesis?
14. What is the purpose of 1st creating a 4-C compound and physically moving it into a
different place for the Calvin cycle to occur in C4 photosynthesis?
15. How and why might the ratio of C4 to C3 plants become altered as atmospheric CO2
levels increase?
16. CAM photosynthesis is an adaptation for water conservation. How does it conserve
water?
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