1. Calvin Cycle
Melvin Calvin – used C-14 as a tracer to discover the how the cycle works

2. Calvin Cycle 3 steps Carbon dioxide fixation Carbon dioxide reduction
Regeneration of RuBP(ribulose bisphosphate)

3. Carbon Dioxide Fixation
Carbon dioxide from atmosphere attaches to RuBP, a 5 carbon molecule = 6 carbon molecule
Splits into 2 3C molecules called 3PG (phosphoglycerate)
RuBP carboxylase is enzyme in this reaction

4. Carbon Dioxide Reduction
2 3PG (phosphoglycerate) undergoes reduction to G3P in 2 steps
3PG  BPG  G3P
Uses some ATP and NADPH from light reactions

5. Regeneration of RuBP Takes 3 turns of cycle to allow 1 G3P to exit.
For every 3 turns, 5 molecules of G3P are used to re-form 3 molecules of RuBP
5 G3P + ATP(from light reactions) 3 RuBP

8. Importance of Calvin Cycle
G3P is the product of the Calvin cycle
G3P can be converted to many organic molecules
Metabolism of G3P can result in Glucose phosphate
Can use to metabolize energy needed
Combine with fructose to produce sucrose, used in transport in plants
Starting point for starch and cellulose
Hydrocarbon skeleton can be used to make fatty acids and glycerol
Nitrogen and hydrocarbon skeleton can make AA’s

9. Other types of photosynthesis
C3 plants – most green plants (azaleas, maples)
Use RuBP carboxylase to fix carbon
Photorespiration – when oxygen levels are high, carbon dioxide levels are low, oxygen combines with RuBP and only 1 molecule of 3PG is made and Carbon dioxide is released.

10. C4 photosynthesis (corn, crabgrass…)
Arranged differently than C3 plants
Mesophyll cells surround the bundle sheath cells
Bundle sheath cells and mesophyll cells have chloroplasts
Use PEP carboxylase to fix carbon dioxide  PEP, to form oxaloacetate ( a 4 carbon molecule) within mesophyll cells which is pumped into the bundle sheath cells, where Carbon dioxide enters the Calvin cycle

11. C4 plants have an advantage over C3 plants in the hot, dry climates because they do not enter photorespiration.
Think about it!!

12. CAM photosynthesis CAM – Carassulaceae acid metabolism
Family of succulent plants (includes cacti)
At night, plants use PEPCase to fix some CO2 forming C4 molecules
During day, C4 molecules release CO2 to the Calvin cycle…