Lecture 12 - C4 Reactions

Question 1

Reaction 1

Answer 1

Phosphoenolpyruvate -> oxaloacetate

Question 2

Enzyme of reaction 1

Answer 2

Phosphoenolpyruvate carboxylase

Question 3

Cofactor of reaction 1

Answer 3

• CO2 in

- Pi out

Question 4

Delta G of reaction 1

Answer 4

-28.6 kJ/mol

Question 5

What is the general purpose of reaction 1?

Answer 5

Incorporation of CO2

Question 6

What is the general purpose of reaction 2?

Answer 6

Reduction of ketone to OH

Question 7

Reaction 2

Answer 7

Oxaloacetate -> Malate

Question 8

Enzyme of reaction 2

Answer 8

Malate dehydrogenase

Question 9

Cofactor of reaction 2

Answer 9

NADPH + H+ -> NADP+

Question 10

Delta G of reaction 2

Answer 10

-29.7 kJ/mol

Question 11

What is the general purpose of reaction 3?

Answer 11

Release of CO2 in the bundle sheath cell to increase the CO2 concentration for more efficient use of rubisco

Question 12

Reaction 3

Answer 12

Malate -> pyruvate

Question 13

Enzyme of reaction 3

Answer 13

Malic enzyme

Question 14

Cofactor of reaction 3

Answer 14

• NADP+ -> NADPH + H+

- CO2 out

Question 15

Where does the released CO2 from reaction 3 go?

Answer 15

To ribulose bisphosphate carboxylase

Question 16

Delta G of reaction 3

Answer 16

+1.7 kJ/mol

Question 17

What is the general purpose of reaction 4?

Answer 17

Regeneration of PEP

Question 18

Reaction 4

Answer 18

Pyruvate -> phosphoenolpyruvate

Question 19

Enzyme of reaction 4

Answer 19

Pyruvate orthophosphate dikinase

Question 20

Cofactor of reaction 4

Answer 20

ATP -> AMP + PPi

Question 21

What is the purpose of C4 reactions?

Answer 21

To make better reaction conditions for rubisco, in the form of higher [CO2], making CO2 fixation more efficient with less oxidation reactions