Transcript Light Reactions/Calvin Cycle

Today:
-Genetics and Evolution of Photosynthetic Systems
-Regulation of the Photosynthetic Machinery
-Carbon reactions: Calvin-Benson cycle
What are the main open questions
about the origin of oxygenic
photosynthesis?
Which are the current hypothesis
to explain the beginning of
oxygenic photosynthesis?
Clicker question: What are the main open questions
about the origin of oxygenic photosynthesis?
1.Do cyanobacteria have two photosystems?
2.How did organisms end up with two photosystems?
3. When did oxygenic photosynthesis originate?
4. Why is oxygenic photosynthesis so important?
A. 1, 2
B. 3, 1
C. 2,3
D. 2,3,1
E. 4,2
Clicker question:
Which are the current hypothesis to explain the
beginning of oxygenic photosynthesis (=two PS)?
1. Microbes adapted some photosynthesis genes from
other metabolic pathways.
2. Gene transfer among early photosynthetic microbes.
3. The formation of chloroplasts.
4. The evolution of one photosynthesis from the other.
A. 1
B. 2
C. 1,2
D. 3,4
E. 1,2,4
Why is oxygenic photosynthesis such and "upgrade"?
Clicker question:
Which of these statements is false?
A. Most chloroplast proteins are imported from the
cytoplasm.
B. The chloroplast genome encodes most of the
chloroplast proteins.
C. Chloroplast genes exhibit maternal inheritance.
D. Most chloroplast proteins are encoded in the nucleus.
Today:
-Genetics and Evolution of Photosynthetic Systems
-Regulation of the Photosynthetic Machinery
-Carbon reactions: Calvin-Benson cycle
PHOTOPROTECTION
"Nonphotochemical
quenching"
Today:
-Genetics and Evolution of Photosynthetic Systems
-Regulation of the Photosynthetic Machinery
-Carbon reactions: Calvin-Benson cycle
ATP
Light Reactions
H2 0
O2
Carbon
Reactions
NADPH
CO2
CH20
Julius Sachs (~1862): 6 CO2 + 6 H2O + solar energy  C6H12O6 + O2.
Glucose/Starch
Calvin, Benson, Bassham (1950)
C14 CO2
Hot ethanol
30 sec
Malic acid
Glucose
Citric acid
Aspartic acid
PEP
Sucrose
Triose phosphates
Triose phosphates
PGA
Sugar-P
Sugar-DiP
5 sec
Malic acid
Citric acid
PEP
Triose phosphates
PGA
Sugar-P
Sugar-DiP
Which is the acceptor of CO2?
CO2
?
3PGA
H
|
H-C-OP
|
H-C-COOH
|
H
Which enzyme catalyzes this reaction?
CO2
Ribulose-1,5bisphosphate
H
|
H-C-O-P
|
H-C=O
|
H-C-OH
|
H-C-OH
|
H-C-O-P
|
H
2x 3PGA
H
|
H-C-O-P
|
H-C-COOH
|
H
3-Phosphoglyceric acid
(3PGA)
STARCH
Clicker Questions
What do these reactions need? A. ADP B. ATP C. NADPH D. NAPDH and ATP D. sugar
Where do these occur? A. Thylacoids B. cytosol C. Stroma
Is all 3-PGA converted to starch? A. Yes B. No
3PGA
1,3-Bisphosphoglycerate Glyceraldehyde-3-P
Triose-P
Topics:
1.Carbon fixation: Calvin Cycle
2.Regulation of the Calvin Cycle
3.Photorespiration
Regulation of the Calvin cycle
Clicker Question:
When should the Calvin Cycle be activated?
A. Darkness
B. Light
C. All the time