e. Both a and c

51. A suspension of algae is incubated in a flask in the presence of both light and CO2. When it is transferred to the dark, the reduction of 3-phosphoglycerate to glyceraldehyde 3-phosphate is blocked, and the concentration of ribulose bisphosphate (RuBP) declines. Why does the RuBP concentration decline?
a. Ribulose bisphosphate is synthesized from glyceraldehyde 3-phosphate.
b. Glyceraldehyde 3-phosphate is converted to glucose.
c. Ribulose bisphosphate is used to synthesize 3-phosphoglycerate.
d. Both a and b
e. Both a and c

e. 1,5-ribulose bisphosphate.

52. During CO2 fixation, CO2 combines with
a. NADPH.
b. 3PG.
c. G3P.
d. water.
e. 1,5-ribulose bisphosphate.

b. the light reactions.

53. The NADPH required for the reduction of 3PG to G3P comes from
a. the dark reactions.
b. the light reactions.
c. the synthesis of ATP.
d. the Calvin cycle.
e. oxidative phosphorylation.

c. during the light reactions.

54. The NADPH required for CO2 fixation is formed
a. by the reduction of O2.
b. by the hydrolysis of ATP.
c. during the light reactions.
d. in C4 plants only.
e. in the mitochondria.

a. can become more acidic.

55. In bright light, the pH of the thylakoid space
a. can become more acidic.
b. can become more alkaline.
c. stays the same; the pH of the thylakoid space never changes.
d. can become neutral.
e. None of the above

d. 6

56. How many moles of CO2 must enter the Calvin-Benson cycle for the synthesis of one mole of glucose?
a. 1
b. 2
c. 3
d. 6
e. 12

b. attached to carbon and hydrogen to form sugar (G3P).

57. After the removal of carbon, the oxygen in CO2 ends up
a. as atmospheric oxygen.
b. attached to carbon and hydrogen to form sugar (G3P).
c. in the soil.
d. attached to hydrogen to form water.
e. as rubisco.

c. 3PG.

58. When CO2 is added to RuBP, the first stable product synthesized is
a. pyruvate.
b. ribulose 1,5-bisphosphate.
c. 3PG.
d. ATP.
e. glyceraldehyde 3-phosphate (G3P).

b. using light and simple chemicals to make reduced carbon compounds.

59. Heterotrophs are dependent on autotrophs for their food supply. Autotrophs can make their own food by
a. feeding on bacteria and converting the nutrients into usable energy.
b. using light and simple chemicals to make reduced carbon compounds.
c. synthesizing it from water and CO2.
d. All of the above
e. None of the above

e. All of the above

60. How is the Calvin cycle connected to the light reactions?
a. The light-induced pH changes activate rubisco.
b. The light-induced electron flow changes the shape of four Calvin-cycle enzymes.
c. The Calvin cycle needs the ATP produced in the light reactions.
d. None of the above
e. All of the above