Light Independent reactions

all quantities of stuff (eg ATP) is based off of making ONE glucose

why do we store energy as organic compounds

• glucose is more stable form of energy storage

• can be mobilized around the plant wherever it’s required

• provides plants with energy even when it’s dark/winter

where calvin cycle takes place

stroma

3 basic stages of calvin cycle

• carbon fixation

• reduction

• regenerating RuBP

rubisco

• adds CO2 to RuBP in carbon fixation stage

• large and slow enzyme 3 reactions/sec

• plants need a shat ton of rubisco for the calvin cycle, thus most abundant protein on earth

carbon fixation (stage 1)

• 6 CO2 (1C) enters and is attached to 6 RuBP (5C) → 6C molecule

  • catalyzed by rubisco

• 6C compound is unstable and immediately breaks down into 12 3-PGA (3C)

reduction (stage 2)

• 3-PGA is in a low energy state

• 3-PGA gets P group from ATP (12 ATPs) to make 12 1,3-bisphosphoglycerate (1,3-BPG)

  • every molecule needs 1 ATP

• 1,3-BPG is reduced by 12 NADPH, it donates 2 electrons, turning it into G3P

• 12 G3P made, 2 leave the cycle to make glucose (10 stay)

**ATP and NADPH are from light reactions

regenerating RuBP (stage 3)

use 6 ATP as energy to rearrange G3P to make 6 RuBP (5C). 1 ATP per RuBP. Cycle repeats.

how many spins of calvin cycle does 1 glucose need?

6 spins; most G3P used to regen RuBP