Chapter 18- photosynthesis (Calvin cycle)

Advantage and disadvantages of cyclic electron flow

A: supplements ATP synthesis

D:no NADPH production and no O2

What uses chemiosmosis to generate ATP

Mitochondria and chloroplasts

What concentration is the H+ pumped across?

Region of low H+ to high H+

In chemiosmosis what drives ATP synthase

The H+ diffusing across the membrane

What are the 3 phases of the Calvin cycle ?

-carbon fixation

-reduction

-regeneration of RuPP

Phase 1 of the Calvin cycle

Rubisco takes 1CO2 and attaches it to RuBP—→ makes it a 6-carbon intermediate

Intermediate spontaneously splits into 3 carbon sugar, 3-phosphoglycerate

Each ‘turn’ of the cycle fixes one CO2, but bc the output is a 3C sugar, its easier to depict the cycle fixing 3CO2 at once

Phase 2 of the Calvin cycle

Each molecule of 3-phosphoglycerate receives an additional phosphate (from ATP produced via light reactions)—→ becomes 1, 3-biphosphatoglycerate

Loses a phosphate, gets reduced by NADPH to form G3P

1 molecule of G3P is removed from the cycle to make glucose and other organic molecules

Phase 3 of Calvin cycle

The remaining G3P are used to complete the cycle to regenerate RuBP, consumes ATP

What 2 molecules can rubisco not discriminate between

CO2 an O2 as the structures are very similar

What is produced when CO2 is added to the 5C RuBP?

Two 3-phosphoglycerates after the unstable 6C sugar splits in 2

What happens when O2 is added to RuBP

One 3PG and one 2-phosphoglycolate are produced, the 2PGo I must be recycled in a process called photorespiration that consumes ATP-wasteful

How often rubisco does this is mostly dependent on:

CO2/O2 concentration ratio in chloroplast

Temperature

Where does photosynthesis in a normal C3 plant occur?

In mesothelioma cells in the middle of the leaf