Key Concepts in Citric Acid Cycle and Metabolism

Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which compound would be expected to decrease in concentration?

Fumarate.

What is the purpose of phosphorylating glucose in the cytosol?

trap glucose in the cell, destabilize it, and facilitate the next series of metabolic steps.

Which term best describes the citric acid cycle?

Amphibolic.

Which process is NOT a metabolic fate for pyruvate in liver tissue?

Phosphorylation to phosphoenolpyruvate.

What are possible sources for acetyl-CoA that enters the citric acid cycle?

1. Oxidative decarboxylation of pyruvate, 2. β oxidation of fatty acids, 3. Catabolism of certain amino acids.

Which citric acid cycle intermediate is chiral?

Malate.

What combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA?

TPP, lipoate, and NAD+.

When is the consumption of acetyl-CoA by the citric acid cycle decreased?

When the demand for ATP is low.

Which enzyme's reaction is NOT linked to the reduction of NAD+?

Succinate dehydrogenase.

Which of the following is not a difference between NADH and FADH2?

ability to act as a reducing agent

Each molecule of acetyl-CoA oxidized by the citric acid results in the net production of ______ molecule(s) of _______

One; FADH2.

For the reaction, 🔺 G’° =29.7 kJ/mol.

L-Malate + NAD+→ oxaloacetate + NADH + H+

The reaction as written:

occurs in cells because of the continual removal of oxaloacetate by citrate synthase

In mammals, what process does NOT occur during the citric acid cycle?

Net synthesis of oxaloacetate from acetyl-CoA.

Anaplerotic reactions:

produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates.

What is substrate-level phosphorylation?

ATP synthesis when the phosphate donor is a substrate with a high phosphoryl-transfer potential.

Which intermediate of the citric acid cycle is prochiral?

Citrate.

Intermediates in the citric acid cycle are used as precursors in the biosynthesis of:

Sterols, nucleotides, amino acids, and fatty acids.

Where do the two molecules of CO produced in the first turn of the citric acid cycle originate?

From the carboxyl group of acetate and a carboxyl group of oxaloacetate.

Which statement about the oxidative decarboxylation of pyruvate in animal cells is correct?

It only occurs under aerobic conditions.