MP8 - Light-Independent Reactions

Light-independent reactions occur in the

stroma

What is the purpose of light-independent reactions?

to fix carbon dioxide

What does fix mean in the terms to fix CO2?

convert unusable energy to useable energy

What are the end products enter the light-dependent reations?

NADPH and ATP

Gaseous CO2 (inorganic) will go through Calvin cycle and be

reduced to become an organic solid (in glucose)

What is the enzyme that with help in carbon fixation?

RuBisCo

What are the 3 phases of the calvin cycle?

1. Carbon Fixation

2. Reduction

3. Regeneration

What occurs during carbon fixation?

CO​₂​​ molecule combines with a five-carbon acceptor molecule,RuBP making two molecules of 3-PGA, catalyzed by rubisco

What occurs during reduction?

ATP and NADPH are used to convert the 3-PGA molecules into molecules of a three-carbon (G3P).

What occurs during regeneration?

1 G3P molecule makes glucose while others recycle to make RuBP acceptor using ATP known as a carbohydrate scramble

CO2 must enter the Calvin cycle _ times to produce 1 (6C) glucose

2

The first phase is carbon fixation: 3 CO2 (1C inorganic compound) enters the Calvin cycle to with 3 molecules of ribulose–1, 5–bisphosphate (RuBP – 5C) to form

6 3PGA (fixed by RuBisCO enzyme)

The second phase is reduction: each of the 6 molecules of 3-phosphoglycerate gets phosphorylated from the hydrolysis of 6 ATP which makes 6 molecules of 1,3-bisphophoglycerate; it is then reduced by

• 6 NADPH 🡪 NADP+ and inorganic phosphate and 6 G3P (glyceraldehyde 3-phosphate)

1 molecule of G3P goes to eventually produce

glucose

The third phase is regeneration: the other 5 molecules of G3P rearrange themselves (by being phosphorylated by ATP) to reform

3 (5C) RuBP (the CO2 acceptor) to enter the cycle again – 1 inorganic phosphate “missing” is actually on 1 RuBP that is short a phosphate

After ____ cycles, 1 glucose is produced and 1 G3P

3

The ____ is required to add energy to form G3P

ATP

The NADPH is important to reduce 3-phosphoglycerate to

G3P