problem set # 7

Question 1

) If a molecule is called a decoupler (or uncoupler) what does that molecule do and how
does it affect ATP synthesis in chloroplast and/or mitochondria?

Answer 1

A decoupler defuses a membrane proton gradient by carrying the protons
through the membrane. Decouplers would decrease ATP production in both
chloroplasts and mitochondria.

Question 2

What is the difference between a chemical and an electrical potential across a membrane?

Answer 2

A chemical potential exists across a membrane when there exists a
difference in the concentration of a compound on one side of the membrane
vs. the other.
An electrical potential exists across a membrane when there is a difference
in the net charge of compounds on one side of the membrane vs. the other.

Question 3

The TCA cycle is an important part of respiration. Where does this metabolic process take
place?

Answer 3

mitochondrial matrix

Question 4

What are the TCA cycle’s 2 major products?

Answer 4

CO2 and NADH

Question 5

What are the four phases of the Calvin cycle? `

Answer 5

Carboxlyation
reduction
transport
regeneration

Question 6

what happens during carboxylation?

Answer 6

: RubisCO catalyzes the condensation of ribulose bisphosphate with
CO2 and resulting cleavage into two molecules of 3-phosphoglycerate

Question 7

what happens during reduction?

Answer 7

: ATP and NADPH are used to convert 3-phosphoglycerate to triose
phosphates: dihydroxyacetone phosphate and glyceraldehydes 3-phosphate

Question 8

what happens during transport?

Answer 8

: triose phosphate exported from the chloroplast (one for every 3 CO2
fixed)

Question 9

what happens during regeneration?

Answer 9

takes 5 (3 carbon) triose phosphate molecules and converts them
to 3 (5 carbon) ribulose 1,5-bisphosphate molecules

Question 10

How do plants compensate for RubisCO’s the slow rate of catalysis?

Answer 10

They make more rubisCO (~50% of protein in green tissues of C3 plants)

Question 11

Label the reactions shown below as an example of a reaction catalyzed by one following
enzyme types: Isomerase, phosphatase, kinase, aldolase, transketolase, & epimerase.

Answer 11

STUDY IN PROBLEM SET

Question 12

RubisCO catalyzes a reaction where O2 instead of CO2 reacts with ribulose-1,5-bisphosphate.
What is this reaction called?

Answer 12

oxygenase reduction

Question 13

What are the immediate products of oxygenase reduction?

Answer 13

3- Phospho glycerate and 2-phosphoglycolate

Question 14

Plants have a metabolic process to recover 75% the carbon lost in this side reaction but it
consumes ATP, NADH, NADPH and looses 25% of the carbon as CO2. What is this process
called?

Answer 14

photorespiration

Question 15

The partitioning between the O2 side-reaction and the carboxylation reaction of RubisCO is
determined by the relative O2 and CO2 concentrations. When the CO2 concentration is too low
the amount of CO2 fixed by photosynthesis can equal the amount of CO2 generated recovering
from the side reaction. What is this point called?

Answer 15

compensation point

Question 16

How does CO2 enter a leaf? What loss is balanced with CO2 uptake?

Answer 16

CO2 diffuses into the plant cell from the air, and water escapes from the plant to
the air, through stomata

Question 17

For the following crop species, indicate whether they are C3, C4 or CAM carbon assimilation
pathway plants:
corn
wheat
barley
pineapple
sugarcane
rice

Answer 17

corn: C4
wheat: C3
Barley: C3
Pineapple: CAM
Sugarcane: C4
Rice: C3