Regulation C4 and CAM Flashcards Preview

Light and Carbon Reactions of Photosynthesis > Regulation C4 and CAM > Flashcards

Flashcards in Regulation C4 and CAM Deck (22):
1

What does calvin cycle activity depend on

Environmental conditions e.g. pH, Mg2+, NADPH

2

What is the optimum pH for the light reaction

pH8

3

How does Rubisco activate>

Uses hydrolysis of ATP to open active site loop (activase_

4

Example of Rubisco inhibitor

CA1P - some plants make this compound - degraded by CA1P phosphatase and removed from Rubisco by activase

5

Thioredoxin

12kDa protein containing key cysteines with redox active S-S. Reduced form activates many enzymes

6

How do you get reduced form of thioredoxin

Coupled to ferredoxin activity via ferredoxin-thioredoxin reductase (4Fe-4S cluster)

7

How are enzymes inactivated

CP12 small intrinsically disordered protein with conserved cysteine residues

8

How does regulatory inhibition occur

Disulphide bond formation

9

Oxidised form of CP12

Binds GAPDH and PRK (found on either side of rubisco) - forms inactive complex

10

What is the CO2 compensation point

[CO2] needed for net photosynthesis

11

How do plants withstand water-stress

Suppress photorespiration by C4

12

How are high rates of wasteful photorespiration reduced

Concentrate CO2 close to the site of calvin cycle enzymes

13

What do C4 compounds enable CO2 to do

Spatially transfer CO2 from mesophyll cells to bundle-sheath cells (costs energy +12ATP)

14

How much does it cost to move 1 CO2

2 ATP

15

How are C4 plants highly productive

Adapt to high temp and low CO2,more resistant to water stress, more productive

16

CAM

Crassulacean acid metabolism - mostly desert xerophytes (tend to be slow growing and resistant to water stress)

17

How do CAM (C4) plants work

Stomata close in day to prevent water loss and stop CO2 absorption. At night CO2 in and fixed into malate by C4 stored in vacuoles for use in the day

18

Avoiding photorespiration

C4 & CAM, concentrate CO2 around rubisco, increase Co2:O2 ratio, decrease oxygenation, costs extra ATP

19

What is role of C4 and CAM

Biochemical pumps to concentrate CO2 in cells and to reduce photorespiration

20

CCM

Carbon concentrating mechanisms in cyanobacteria

21

What is rubisco regulated by

Mg2+ and pH

22

Carboxysome

Class of bacterial microcompartments - contains rubisco and carbonic anhydrase inside - CO2 rich - not in chloroplasts