How Cells Acquire Energy Photosynthesis. Chapter 6a. Carbon and Energy Sources. Photoautotrophs Carbon source is carbon dioxide Energy source is sunlight Heterotrophs Get carbon and energy by eating autotrophs or one another. Photoautotrophs .
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Bacteria congregated where red and violet wavelengths illuminated alga
Bacteria moved to where algal cells released more oxygen--areas illuminated by the most effective light for photosynthesis
Organelles of photosynthesis
6O2 + C6H12O6 + 6H2O
12H2O + 6CO2
carbon dioxide uptake
ADP + Pi
Shortest Gamma rays
Longest Radio waves
Chlorophylls a and b
Main pigments in most photoautotrophs
Wavelength absorption (%)
Red to purple pigments
2H + 1/2O2
pool of electron transporters
electron transport system
Cytochrome b/ f complex
ADP + Pi
Potential to transfer energy (voids)
1/2 O2 + 2H+
Inmesophyll cell, Rubisco affixes O2 to RibuloseBP.
and only one
PGA (not two)
lower CO2 uptake, fewer sugars can form
+ PEP (phosphoenolpyruvate)
in mesophyll cell,
cell carbon fixation
C3 PLANTS. With low CO2 / high O2, photorespiration predominates.
Malate Pyruvate + CO2 .
in bundle-sheath cell, carbon is fixed again
more CO2 in leaf; no photorespiration
(See next slide.)
At night CO2 is high & O2 low . In mesophyll cells, stomata open at night; CO2 uptake but no water loss
PEP + CO2 C4
C4 PLANTS. With low CO2 / high O2, Calvin-Benson cycle predominates during the hot day (stomata are closed to preserve water).
CO2 + C3
Stomata close during day;CO2 is low. Fixed CO2 that accumulated overnight as C4 in leaf is used during day by
Calvin Benson cycle.
Fig. 6.15, p. 102
CAM PLANTS. With low CO2 / high O2, Calvin-Benson cycle predominates.
ADP + Pi
end product (e.g. sucrose, starch, cellulose)