Carbon Fixation

Question 1

Carbon fixation is a ___ reaction.

Answer 1

Dark

Question 2

Function of Carbon Fixation

Answer 2

Use NADPH and ATP to fix carbon dioxide and make glyceraldehyde-3-phosphate

Question 3

Stage 1

Answer 3

Carbon fixation

CO2 fixation catalyzed by the enzyme Rubsico

Question 4

Product of Stage 1

Answer 4

3-phosphoglycerate

Question 5

Most abundant protein in humans

Answer 5

Collagen

Question 6

Most abundant protein in plants

Answer 6

Rubisco

Question 7

Rubisco

Answer 7

Ribulose 1,5-bisphosphate carboxylase-oxygenase

Has 16 subunits (8 large & 8 small)

Less efficient enzyme

kcat (turnover #) ≈ 3 s-1

Question 8

Stage 2

Answer 8

Reduction

Glyceraldehyde-3-phosphate (G-3-P) is the main product of Calvin cycle

Question 9

Stage 3

Answer 9

Regeneration of acceptor

Question 10

What enzymes are regulatory enzymes?

Answer 10

Phosphoribulokinase
Ribulose bisphosphate carboxylase
Fructose bisphosphatase
Sedoheptulose bisphosphatase

Question 11

High Km

Answer 11

Can take more substrate

Question 12

Low Km

Answer 12

Saturated at low levels of substrate

Question 13

The Calvin Cycle occurs in the ____

Answer 13

Stroma

Question 14

Conditions that increase activity of Rubisco

Answer 14

Light
Higher Mg2+ concentration
Higher pH

Question 15

What enzyme activates Rubsico?

Answer 15

Rubisco activase

Question 16

Rubsico is ____ at night

Answer 16

Inactive

Question 17

Rubisco is inhibited by:

Answer 17

CA1P (2-carboxyarabinitol-1-phosphate), which is produced in the dark

Question 18

Four Calvin cycle enzymes and Rubsico activate are regulated by _____

Answer 18

Light-dependent reduced ferredoxin

Question 19

Rubisco, which fixes CO2, also reacts with ____ to produce a metabolically useless product

Answer 19

O2

Question 20

What is the product of a reaction between Rubsico and O2?

Answer 20

2-phosphoglycolate

Question 21

Salvaging 2-phosphoglycolate is costly. This pathway is called _____

Answer 21

Photorespiration

Question 22

In C4 plants (corn), CO2 fixation and Rubisco activity are _____

Answer 22

Spatially separated

Question 23

CAM (Crassulacean Acid Metabolism) plants are adopted to drought

Answer 23

Acidity of vacuole builds up at night as reaction proceeds

Dark: Stomata open
Light: Stomata closed