Kreb's Cycle Flashcards
Which statement about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is CORRECT?
One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate.
Which reaction of the citric acid cycle requires a water molecule?
a) formation of citrate
b) succinyl-CoA to succinate
c) fumarate to malate
d) All of the answers are correct
All of the answers are correct
Which statement about NAD + and NADH is TRUE?
NADH inhibits the pyruvate dehydrogenase complex.
Which statement is NOT true of the reaction catalyzed by the pyruvate dehydrogenase complex?
Biotin participates in the decarboxylation.
How much carbon dioxide is produced from the complete aerobic catabolism of one molecule of 2-phosphoglycerate via catabolic pathways?
3 CO2
The glyoxylate cycle is:
a means of using acetate for both energy and biosynthetic precursors
Which enzyme catalyzes a reversible reaction under normal cellular conditions?
succinate dehydrogenase
Covalent modification is one way the activity of specific enzymes can be regulated. Which enzyme is NOT regulated in this way?
a-ketoglutarate dehydrogenase
Which enzyme in the citric acid cycle has a standard free energy that is large and positive?
malate dehydrogenase
Which statement about the oxidative decarboxylation of pyruvate in animal cells is CORRECT?
It only occurs under aerobic conditions.
Which enzymatic activity would be decreased by thiamine deficiency?
a-ketoglutarate dehydrogenase complex
In mammals, what process does NOT occur during the citric acid cycle?
net synthesis of oxaloacetate from acetyl-CoA
Which three of the choices listed are possible sources for acetyl-CoA that enters the citric acid cycle?
- oxidative decarboxylation of pyruvate
- B-oxidation of fatty acids
- catabolism of certain amino acids
- citrate
- carboxylation of pyruvate
Oxidative decarboxylation of pyruvate
B-oxidation of fatty acids
Catabolism of certain amino acids.
1,2 and 3.
Which cofactor is required for the conversion of fumarate to succinate?
FADH2
Which citric acid cycle intermediate is chiral?
Malate
Which statement is FALSE with respect to the pyruvate dehydrogenase complex?
The proximity of the catalytic enzymes in the cluster slows down the overall rate.
Which cofactors associated with the pyruvate dehydrogenase complex are classified as prosthetic groups?
1) TPP
2) lipoate
3) CoA-SH
4) NAD +
5) FAD
1,2 and 5
TPP, Lipoate, FAD
Which high-energy bond is associated with the succinyl-CoA synthetase reaction?
a) acyl phosphate
b) thioester
c) phospho-histidine
d) mixed anhydride
e) All of the answers are correct.
E) All of the answers are correct.
Entry of acetyl-CoA into the citric acid cycle is DECREASED when:
the ratio of [ATP]/[ADP] is high.
During seed germination, the glyoxylate pathway is important to plants because it enables them to:
carry out the net synthesis of glucose from acetyl-CoA.
Why is flux through the citric acid low in the resting state?
Flux through the cycle is low due to low local concentrations of NAD+ because of a diminished rate of oxidative phosphorylation.
The glyoxylate cycle in germinating seeds is a pathway that has some similarity to the citric acid cycle. It uses the carbon-based products from the catabolism of fatty acids as the precursors for gluconeogenesis. How can the glyoxylate cycle accomplish this?
Its reactions bypass the decarboxylation steps of the citric acid cycle.
What process occurs in the citric acid cycle?
formation of a mixed anhydride (acyl phosphate)
Conversion of 1 mol of acetyl-CoA to 2 mol of CO 2 and CoA via the citric acid cycle results in the net production of:
1 mol of FADH2.
Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?
TPP, lipoic acid, and NAD+
