exam

Question 1

chloroplasts make O2 when illuminated in presence of an artificial e- acceptor (not NADP). will they still produce glucose?

Answer 1

no, NADPH is required in the calvin cycle for glucose synthesis to continue. since there is no NADPH produced, the calvin cycle will halt

Question 2

why can C4 plants thrive at low [CO2] that do not support the growth of C3 plants

Answer 2

C4 plants fix CO2 by bringing it into the mesophyll cell as HCO3- and then reacting it to form malate which is transported to the bundle sheath cell. This increases Rubisco efficiency by delivering the correct CO2 substrate (as opposed to O2) and allows C4 plants to thrive w/ low CO2 levels

C3 plants fix CO2 immediately and at low concentrations of CO2, O2 may be used as a substrate more

Question 3

why do C3 plants continue to increase photosynthetic activity at high CO2 concentrations when C4 plants reach a plateau?

Answer 3

C4 plants reach a plateau because even at high [CO2] they still must undergo more reactions to reach Rubisco

C3 plants react CO2 with ribulose 1,5 bisP immediately in the dark rxns so it can increase its photosynthetic activity proportionally to the concentration of CO2 b/c it doesnt have the extra rxns C4 plants have

Question 4

oxidative decarboxylation

Answer 4

uses NADP –> NADPH, H+, CO2

Question 5

hydrolase

Answer 5

uses H2O to cleave

Question 6

mutation in triose phosphate isomerase, diff in C4 vs. C3?

Answer 6

this mutation would prevent the conversion of G-3-P to dihydroxyacetone phosphate, and stop gluconeogenesis from continuing. G-3-P will buildup

no difference in C3/C4 plants b/c they both enter calvin cycle at 3-phosphoglycerate

Question 7

mutation in phosphoglycerate mutase

Answer 7

no effect on carbon assimilation because the calvin cycle intersects gluconeogenesis at 3-phosphoglycerate, which is higher up

Question 8

mutation in pyruvate carboxylase

Answer 8

no effect on carbon assimilation because pyruvate carboxylase is used to generate oxaloacetate at the bottom of gluconeogenesis

C4’s oxaloacetate is generated through a different process

Question 9

mutation in malate dehydrogenase

Answer 9

C3 plants unaffected

C4 plants would be unable to reach the carbon assimilation rxns in the bundle sheath cell because malate formation would stop and a buildup of oxaloacetate would form

Question 10

aconitase

Answer 10

calvin cycle and C4 cycle would be unaffected because G-3-P can still be made in the dark rxns.