Citric Acid Cycle Overview

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What is another name for the citric acid cycle?

Tricarboxylic acid cycle (correct)
Glycolysis cycle
Beta-oxidation cycle
Oxidative phosphorylation cycle

Where does the citric acid cycle occur in the cell?

Cytosol
Nucleus
Mitochondria (correct)
Endoplasmic reticulum

Which molecule is the major source of acetyl CoA for the citric acid cycle?

Fructose
Glycerol
Pyruvate (correct)
Glucose

What is the final electron acceptor in the citric acid cycle?

Oxygen (O2) (A) Signup and view all the answers

Which of the following is converted to CO2 in the citric acid cycle?

Carbon skeletons of carbohydrates, amino acids, and fatty acids (D) Signup and view all the answers

What is the overall importance of the citric acid cycle in metabolism?

Oxidative catabolism of carbohydrates, amino acids, and fatty acids (A) Signup and view all the answers

What is the role of the pyruvate dehydrogenase complex (PDH complex)?

To convert pyruvate to acetyl CoA in the mitochondria (C) Signup and view all the answers

Which coenzyme is required for the enzyme pyruvate carboxylase (E1) in the PDH complex?

Thiamine pyrophosphate (TPP) (C) Signup and view all the answers

What is the role of citrate synthase in the citric acid cycle?

To catalyze the condensation of acetyl CoA and oxaloacetate to form citrate (D) Signup and view all the answers

Which statement about aconitase is correct?

It isomerizes citrate to isocitrate (A) Signup and view all the answers

What is the primary means of regulation for citrate synthase?

Substrate availability (C) Signup and view all the answers

Which of the following is NOT a coenzyme required by the PDH complex?

Adenosine triphosphate (ATP) (D) Signup and view all the answers

What is the role of aconitase in the TCA cycle?

Aconitase is inhibited by the plant toxin fluoroacetate. (C) Signup and view all the answers

What is the role of isocitrate dehydrogenase in the TCA cycle?

Isocitrate dehydrogenase catalyzes the irreversible oxidative decarboxylation of isocitrate. (A) Signup and view all the answers

What is the role of the α-ketoglutarate dehydrogenase complex in the TCA cycle?

The α-ketoglutarate dehydrogenase complex is inhibited by its products, NADH and succinyl CoA. (C) Signup and view all the answers

What is the role of succinate thiokinase in the TCA cycle?

Succinate thiokinase is a substrate-level phosphorylation reaction in the TCA cycle. (D) Signup and view all the answers

What is the role of succinate dehydrogenase in the TCA cycle?

Succinate dehydrogenase catalyzes the oxidation of succinate to fumarate. (C) Signup and view all the answers

Which statement about the TCA cycle is true?

The TCA cycle releases three CO2 molecules. (D) Signup and view all the answers

What is the role of fumarase in the citric acid cycle?

It catalyzes the hydration of fumarate to malate (C) Signup and view all the answers

How many pairs of electrons are transferred during one turn of the citric acid cycle?

Four pairs, three reducing $NAD^+$ and one reducing $FAD$ (C) Signup and view all the answers

What is the primary factor that regulates the citric acid cycle?

The supply of oxidized cofactors ($NAD^+$ and $FAD$) (D) Signup and view all the answers

Which of the following enzymes is NOT mentioned as being important for the regulation of the citric acid cycle?

Malate dehydrogenase (C) Signup and view all the answers

What is the fate of the two carbon atoms that enter the citric acid cycle as acetyl-CoA?

They are released as $CO_2$ (B) Signup and view all the answers

What is the primary factor that determines the rate of ATP utilization, which in turn regulates the citric acid cycle?

The rate of chemical and physical work in the cell (B) Signup and view all the answers