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9/20/2016
Bio100 (Paddack) Lecture 8 (9/19/16): Photosynthesis
I. Photosynthesis
A. Sunlight
B. Anatomy of leaf
C. Photosynthesis (C3 pathway)
1. Light reaction
i. Capture photon
ii. Use energy from photon to split water
iii. Use electron from splitting water to synthesize ATP & NADPH
2. Calvin cycle
i. Uptake of CO2
ii. Synthesis of 3-C compound (PGA)
iii. Synthesis of 6-C compound (glucose)
D. Photosynthesis constraints & solutions
1. C4 photosynthesis (spatial separation of cycles)
2. CAM photosynthesis (temporal separation of cycles)
Photosynthesis
Photoautotrophs- Organisms that use the sun’s
energy to make food
Trees, flowers
Wheat
Algae (a Protist)
Cyanobacteria
Fig. 7.1
In plants and algae, photosynthesis occurs
in chloroplasts
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Figure 5.6 Absorption Spectra of Plant Photosynthetic Pigments
Figure 7.6B
The Light Reactions
• Photons hit chlorophyll
molecules
– This knocks electrons to
a higher energy level
The Light Reactions
• A Reaction
Center captures
the energy from
excited electrons
Figure 7.7B
Figure 7.7A
The Light Reactions
• Electrons are passed through an Electron Transport Chain
to produce ATP and reduce NADP+ to NADPH
ATP is produced through Chemiosmosis!
Figure 7.9
Figure 7.9
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Light Reactions
Summary of the Light Reactions…
H2 O
Dark Reactions
½ O2 + 2 H+
Transferred to
Light Energy
NADPH
ATP
The Dark Reactions
(The Calvin Cycle)
• Requires energy from ATP and
NADPH
• Takes carbon from CO2 to make
G3P
• Glucose is made from 2 G3P
Figure 7.10
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C4 Cycle
Figure 5.17 Examples of Plants with the CAM Photosynthetic Pathway
Figure 5.16 Crassulacean Acid Metabolism (Part 1)
Figure 5.16 Crassulacean Acid Metabolism (Part 2)
Figure 5.15 C3, C4, and CAM Photosynthesis Compared
Calvin Cycle
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Lecture 8 (9/19/16): Photosynthesis
1. Define: wavelength, photon.
2. Be able to identify the following structures of
plants & state the function of each: stomata,
mesophyll cells, chloroplast, thylakoid, stroma,
chlorophyll.
3. Write the chemical equation for photosynthesis.
4. What does ‘carbon fixation’ mean?
5. List the 2 stages of photosynthesis, noting what
each stage does and what comes out of it.
6. What physical environmental condition have C4
& CAM plants been able to overcome? Briefly, how
do they get around this problem?
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