TCA Cycle

What other "high energy" compound is generated directly by the CAC?

GTP

How many molecules of reduced cofactors are produced by the oxidation of one molecule of acetyl CoA by the CAC?

3 NADH, 1 FADH2

Why is the citric acid cycle said to be amphibolic?

It is said to be amphibolic because it participates in both catabolic & anabolic reactions.

Why is pyruvate dehydrogenase an important enzyme?

Pyruvate dehydrogenase contributes to the conversion of pyruvate to Acetyl CoA which is the starting product for the TCA cycle. Pyruvate dehydrogenase contributes to linking the glycolysis metabolic pathway to the citric acid cycle and releasing energy via NADH

Which of the enzymes of the CAC have been identified as tumor suppressors?

Succinate dehydrogenase & fumarate hydratase. Accumulation of fumarate or succinate inhibits the hydroxylation of proline on hypoxia inducible factors which leads to cell proliferation & angiogenesis.

What four intermediates of the cycle are important for synthesis of other cell constituents, and what are those constituents?

1. Citrate- carbon for fatty acid synthesis & gluconeogenesis, & involved in the inhibition of glycolysis via PFK1 2. α- ketoglutarate- produced glutamate by a transamination rxn which is a very important neurotransmitter 3. Succinyl CoA- Involved in heme synthesis (Succinyl CoA + Glycine + Iron = Heme) 4. Oxaloacetate- Important starting material for glucose synthesis and produces aspartate by a transamination rxn

What is the fuel for the CAC? From what metabolites is it derived?

Acetyl CoA is the fuel for the citric acid cycle. It is derived from the breakdown of fatty acids, amino acids, & glucose (via pyruvate by pyruvate dehydrogenase reaction following glycolysis)

What are its catabolic functions?

Important for the breakdown of fuels (oxidation of fuels)

Where in the cell does the citric acid cycle occur?

In the mitochondria

What are its anabolic functions?

Produces precursors for the synthesis of heme, amino acids, etc.

Why is pyruvate carboxylase an important enzyme? What is its allosteric effector?

Pyruvate carboxylase provides another means of adding carbons into the citric acid cycle in other forms other than Acetyl CoA. It's allosteric effector is Acetyl CoA

What are the other names for the citric acid cycle?

Tricarboxylic Acid (TCA) Cycle & Krebs Cycle