Chapter 10: Calvin Cycle and C4/CAM

Where does the Calvin Cycle occur?

stroma of the plant; it is light-independent

How many cycles for one glucose molecule?

6 cycles per one glucose

Where does the Calvin Cycle occur?

stroma of the plant; it is light-independent

How many cycles for one glucose molecule?

6 cycles per one glucose

How many G3P molecules per one glucose

2 G3P molecules per one glucose

How many Calvin Cycle turns for one G3P molecule?

3 turns per one G3P molecule

Requirements for the Calvin Cycle

18 ATP, 12 NADPH, 6 CO2

How many molecules of CO2 to input?

each cycle = 1 CO2 molecule per

(easier to do 3 CO2 at a time)

Three stages of the Calvin Cycle

Carbon Fixation

Reduction

Regeneration

Rubisco function

the key enzyme responsible for capturing carbon dioxide from the atmosphere and incorporating it into organic molecules

most common protein on Earth (alledgedly)

Carbon Fixation: molecules output

3 CO2 + 3 RuBP (5-carbon) → Short-Lived Intermediate

Short-Lived Intermediate → 6 3-PGA

Reduction: ATP inputs/outputs

needs: 6 ATP → 6 ADP; P added to each 3-PGA

turns into: 6 3-PGA → 6 1,3-BisPGA

Reduction: NADPH inputs/outputs

needs: 6 NADPH → 6 NADP+

donates/loses: pair of e- and the one phosphate

turns into: 6 1,3-BisPGA → 6 G3P

Where does the 6 G3P go?

1 G3P leaves the cycle as an output; the 5 other G3P cycles until all 6 are output

Regeneration: inputs/outputs

needs: 3 ATP → 3 ADP + 2 P

regeneration of RuBP

turns into: 5 G3P → 3 RuBP

C4 Plants

• physical separation of Carbon Fixation (CO2 fixation → PEP)

• PEP Carboxylase

• Costs 1 ATP

• better in hot conditions

ex: corn (maize), sugarcane, sorghum, millet, switchgrass, crabgrass, and amaranth

CAM Plants

• temporarily/temporal separation of Carbon Fixation

• Crassulacean Acid Metabolism

• Store Malate in Vacuoles during Night, Calvin Cycle during day

• better in dry conditions

ex: cacti, pineapple, agave, Opuntia (prickly pear), Kalanchoe (florist kalanchoe), and common iceplant