Metabolic pathways: pyruvate dehydrogenase & TCA Flashcards
What is NAD+ derived from?
Niacin, a vitamin
Why must NAD+ be recycled?
It is in limited supply
NADH must be re-oxidised to allow glycolysis to continue
What is pyruvate converted to in the absence of oxygen?
Ethanol (plants, yeast, microorganisms)
Lactate (animals)
What enzyme catalyses the conversion of pyruvate to lactate?
Lactate dehydrogenase
How is NAD+ recycled?
Further metabolism e.g. conversion of pyruvate to lactate allows re-oxidation of NADH
How many CO2 are released in the Krebs cycle?
2
Where does the TCA cycle occur?
Matrix of mitochondria
Why is it assumed that mitochondria have evolved from captive bacteria?
Mitochondria have their own DNA
What is the pyruvate dehydrogenase complex?
An enzyme system which catalyses the conversion of pyruvate to acetyl-CoA
How many CO2 are released in the pyruvate dehydrogenase complex and why?
1
Pyruvate contains 3 carbons
Acetyl-CoA only contains 2
How does pyruvate get into the mitochondrial matrix?
There are specific transport proteins in the membranes
How many enzymes are involved in the control of the pyruvate dehydrogenase complex?
2
How many enzymes are involved in the actual reaction mechanism of the PDC?
3
How many coenzymes are involved in the PDC?
5
Is the conversion of pyruvate to acetyl co-A reversible or irreversible?
Irreversible
What happens to the acetyl-coA produced in the PDC?
Enters the TCA cycle
What happens in the initial reaction in the TCA cycle?
Acetyl-CoA binds with a four carbon molecule to produce the six carbon citric acid
How many oxidation reactions are involved in the TCA cycle?
4
How many hydrogen molecules are released in one round of the TCA cycle?
3NADH + H+
1 FADH2
What is the four carbon molecule that binds with acetyl-CoA to form citric acid in the initial reaction of the TCA cycle?
Oxaloacetate
What kind of reaction is the conversion of GDP to GTP?
Substrate-level phosphorylation
What is the name of the only enzyme which uses FAD as a co-factor and where is it located?
Succinate dehydrogenase
Located in the inner mitochondrial membrane
How many hydrogen molecules in total are released from glycolysis, the pyruvate dehydrogenase complex and the TCA cycle?
10 NADH + H+
2 FADH2
