MCB 259: PLANT PHYSIOLOGY 1998, Quiz 8 – November 24,
Name (please print):

 

 

 

1. Which type of CO2 fixation utilizes a separation in space between prefixation of CO2 and final fixation in the Calvin cycle?
A) C-3, B) C-4, C) CAM

2 Plants that use the C-4 pathway of CO2 fixation
A) do not have the RubisCO enzyme
B) use the RubisCO enzyme for the final fixation
C) have the RubisCO enzyme, but they do not use it for CO2 fixation

3 What is the name of the molecule that is first carboxylated in C-4 plants? (i.e. the molecule that accepts the CO2)

4 What does the name C-4 photosynthesis refer to?
A) the number of C atoms in the first acceptor of the fixed CO2
B)The number of C atoms in the first product after CO2 fixation
C) the number of intermediates in the pathway

5 Which type of CO2 fixation (C-3 or C-4) will be more effective in CO2 fixation at low CO2 concentrations? A) C-3, B) C-4, C) no difference

6 Which type of CO2 fixation will be more effective under conditions were photosynthesis is limited be gas exchange (low water availability)? A) C-3, B) C-4, C) no difference

7. Which of the two enzymes has the higher affinity for CO2?
A) PEP Carboxylase, B) RubisCO C) both the same?

8. Can You express the same idea in terms of the Michaelis Menten constant?
The PEP carboxylase has a lower/higher/same (circle correct alternative) Km for CO2 as compared to RubisCO.

9. Plants growing in desserts usually have C-4, C-3, CAM metabolism (circle correct alternative)

10 Why do some C-4 plants not have grana thylacoids in their bundle sheath chloroplasts?
A) The chloroplasts in the bundle sheath cells receive sufficient energy rich phosphate bonds in the form of PEP and therefore do not need cyclic electron transport.
B)The chloroplasts in the bundle sheath cells receive sufficient reduction equivalents in the form of malate, and therefore only need cyclic electron transport.
C) The bundle sheath cells do not have the C-3 cycle enzymes, the CO2 is covalently bound but not reduced, no NADPH is needed in this cell type.

11 Increased CO2 concentration can lead to higher rates of CO2 fixation. You expect this effect to be
a) higher in C-4 than in C-3 plants
b) higher in plants with a high CO2 compensation point
c) higher in plants with a low CO2 compensation point.

12 What molecules/isotopes did Calvin and Bassham use to trace the fate of CO2 in photosynthesis?

13 In what molecule and where (in what cell organelle) is CO2 stored in CAM plants at night?

14 At what time of the day would you expect the least acidic pH in the vacuole of a plant with CAM?