Terms in this set (52)
Energy of light Equations
Visible Light spectrum
How is light absorbed to capture the energy?
Cells use chromophores, specifically pie electrons of conjugated double bonds
a molecule that is capable of absorbing incident radiation and capturing energy
Do chromophores absorb all light?
No, each chromophore absorbs specific wavelengths of light
Ways captured energy are released
1)Loss of heat through molecular collision
3)Pass energy in resonance transfer of adjacent molecule.
4) Pass electron in photo-oxidation to adjacent molecule
How is energy released in photosynthesis
Resonance and Photo-oxidation
chlorophyll a and chlorophyll b
What light does B-Carotene absorb
Blue light, appears red/yellow/brown
What light does chlorophyll absorb?
Absorb violet-blue, and orange-red light. appears green
found in red algae cyanobacteria and absorbs yellow light, appears green
Describe phycoerythrin structure
4 cyclopentanes, bottom point has NH group, with various branches
Chromophore Absorption spectra
all of the chromophores together cover the entire light spectrum
Basic photosynthesis reaction
CO2 + 6H2O ---> C6H12O6 + 6O2
What does photosynthesis do?
Carbohydrate synthesis from light, keeps the CO2 and O2 balance in the biosphere
The two sets of reactions for photosynthesis
Light Reactions and Dark reactions
How are the light and dark reactions connected?
NADPH, ATP (reducing power) from light reactions are used in dark reactions for energy
Lipid composition of chloroplast membranes
10% glcerophospholipids; 80% mon/digalactosyl diacylglycerols; 10% sulfolipids
why is the lipid composition of chloroplast membranes important?
The composition makes the membrane very fluid
similar to glycerophosopholipids, lacks phosphate instead galactose, connected to OH, galactose, or sulfo group at 2-Carbon
Way plant evolution occured
Endosymbiosis, from cyanobacteria
4 Plant Light Reactions
1) O2 Evolving Complex (OEC)
2)Light Harvesting Complex
Where to plant light reactions occur?
produces O2, binds 2H2O and produces 4 e- passed to light harvesting complex and 4 H+ pumped into thylakoid lumen for ATP synthesis. 4 Manganese-protein metal cluster
Light Harvesting Complex
antenna pigments surround reaction centers (P680) with 2 in each complex, defined structural units of photosystems.
How is electron transferred between chlorophylls in light harvesting complex
How is electron transferred when exiting reaction center?
Photosystem II electron Transport chain
P680*-->Ph-->Qa-->Qb-->Cytochorme Bf complex
In photosystem II, a molecule that accepts excited electrons from a reaction center chlorophyll and passes them to an electron transport chain.
Carries 2 protons for Cyt bf reduction
Cytochrome bf complex
accepts e- from reduced plastoquinones and passes then to plastocyanin in the lumen. 1 cytochrome f, 2 cytochrome b (+heme) 1 Fe-S protein, 1 bound plastoquinone
Soluble bridge in lumen that links Cyt. Bf to P.S. 1
Photosystem I Electron Transport Path
When is NADPH produced in Photosystem I
The reduction of Ferridoxin, which occurs in the stroma
Sum of the Light Reactions
H2O + 4H+ + 4photons +NADP+ + H+ ----> 1/2O2 + 6H+ +NADPH
Where do the 2 new protons comes from?
Cytochrome Bf, the other 4 come from the water, and all help establish the proton gradient
ATP Synthase Complex
a specialized protein complex embedded in the thylakoid membrane that allows H+ ions to escape from the lumen and uses the resulting energy to generate ATP. Has F0 and F1 substructures with ring that rotates to synthesize ATP
SUM NADPH and ATP synthesized
8 H+ -----> O2 + 2NADPH + 3ATP
The Dark Reactions of photosynthesis
"fix" or reduce atmospheric CO2 into produced carbohydrate
Stages of Calvin Cycle
1) Production/Reduction Stage
2) Regeneration/Recovery Stage
Production Stage Calvin Cycle
a 5-carbon sugar incorporates 1 carbon dioxide to synthesize 2 3-carbon molecules (3-phosphoglycerate) that undergoes phosphorylation and reduction to produce G3P in ATP, NADPH expensive pathway
Regeneration State of Calvin Cycle
The synthesis ribulose 1,5 bisphosphate
Reactions of the Calvin Cycle
Opposite of glycolysis, with the exception that it starts with ribulose 1,5 bisphosphate--->glycerate, ends at glyceraldehyde 3-phosphate
A carboxylase and oxygenase
When Rubisco binds CO2
The synthesis of carbohydrate occurs
When Rubisco binds O2
2C/3C synthesis occurs
8 large subunits for catalysis
8 small subunits for regulation
Regulation of Rubisco
Activation: high levels CO2 allosteric, high levels NADPH, elevated stroma pH
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