L25 Citric Acid Cycle (Krebs/TCA) Flashcards
The citric acid cycle harvests high-energy electrons from…
Carbon fuels
Pyruvate is converted to acetyl CoA by…
Pyruvate dehydrogenase
In step 2 citrate is rearranged to form the unstable molecule…
Isocitrate
Hydroxide is moved along 1 carbon
Citrate is rearranged to isocitrate by…
Aconitase
Isocitrate dehydrogenase converts…
Isocitrate to α-ketoglutarate
During the conversion of isocitrate to α-ketoglutarate:
a) NAD+ → NADH
b) NADH → NAD+
c) FADH2 → FAD
d) GTP → GDP
a) NAD+ → NADH
α-ketoglutarate is converted to…
Succinyl CoA
Succinyl CoA is converted to succinate. This facilitates the conversion…
of GDP to GTP (oxidative phosphorylation)
Succinate dehydrogenase converts…
Succinate to Fumarate
Fumarase converts…
Fumarate to malate
Malase dehydrogenase converts…
Malate to oxaloacetate
The conversion of succinate to fumarate generates…
FADH2
The conversion of Malate to oxaloacetate generates…
NADH
In the final step of the citric acid cycle…
Citrate is regenerated from oxaloacetate and acetyl-CoA via citrate synthase
The citric acid cycle is a:
a) amphibolic pathway
b) catabolic pathway
c) anabolic pathway
a) amphibolic pathway
It generates both catabolic and anabolic metabolites!
Unlike glycolysis, the citric acid cycle is controlled by..
ADP (rather than AMP)
Pyruvate dehydrogenase is a multienzyme complex witH:
a) 5 subunits
b) 3 subunits
c) 213 subunits
d) 132 subunits
d) 132 subunits
Pyruvate dehydrogenase requires Vitamin B1 and which two other nutrients?
- Riboflavin (as FADH2)
* Niacin (as NAD)
Beri-Beri is caused by…
B1 deficiency
In Beri-Beri, pyruvate cannot be converted to…
Acetyl CoA
as there is insufficient B1
Symptoms of Beri-Beri (3)…
- Loss of appetite
- Lassitude (from lack of ATP)
- Numbness (neurons not firing)
Wernicke-Korsakoff encephalopathy is…
B1 deficiency in chronic alcoholics
In addition to being converted to acetyl CoA to use in the citric acid cycle, pyruvate may also be converted to… (4)
- Lipids
- Amino acids
- Lactate
- Ethanol (in yeast and some bacteria)
acetyl CoA is converted to lipids when…
ATP is plentiful
acetyl CoA is converted to amino acids during…
High growth periods
acetyl CoA is converted to lactate under…
Anaerobic conditions
Ecstasy (MDMA) works by…
Inhibiting the pain from lactic acid buildup
Key control points for the citric acid cycle occur at (3)…
- Pyruvate → Acetyl CoA
- Isocitrate → α-ketoglutarate
- α-ketoglutarate → succinyl CoA
High ADP and pyruvate will encourage the conversion of…
Pyruvate → Acetyl CoA
High ATP and high NADH will inhibit citric acid cycle at:
a) Pyruvate → Acetyl CoA
b) Isocitrate → α-ketoglutarate
c) α-ketoglutarate → succinyl CoA
d) All of the above
d) All of the above
