BSCI170: Photosynthesis - Calvin Cycle

What is the VERY BASIC goal of Calvin Cycle?

turning carbon (gas) into G3P (solid)

How many phases are in the calvin cycle?

3:

• carbon fixation

• reduction

• regeneration

Where does the calvin cycle occur?

stroma of chloroplasts

where does the light dependent reactions occur

thylakoids

Carbon fixation

1. 1 carbon from CO₂ attaches to RuBP (5 carbons) through Rubisco, creating an unstable molecule that breaks in 2

2. the unstable molecules breaks into 2 and creates 2 3C molecules called PGA

Reduction

For 1 PGA,

1. 1 ATP turns into ADP

2. 1 NADPH turns into NADP+

3. 1 PGA turns into 1 G3P

since there’s 2 PGA from carbon fixation, double it

Net production:

• 2 ADP

• 2 NADP+

• 2 G3P

Regeneration

(this is after a couple turns of the cycle)

there’s 6 G3P made, but one G3P gets recycled back into the cycle. that leaves 5 G3P to turn into 3 RuBP

Produces (for 5 G3P):

• 3 RuBP

• 3 ADP

What is G3P used for

synthesizing:

• carbohydrates

• fatty acids

• amino acids

some G3P stays in chloroplast, others leave into the cytoplasm

What does the stroma make with G3P

amino acids, starch, fatty acids, glucose (through starch)

what does the chloroplast make

sucrose (eventually breaks down into glucose and fructose)