Biochemistry of Glycolysis and TCA Cycle

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Questions and Answers

What is the primary molecule that enters the tricarboxylic acid cycle?

NADH

Fumarate

Acetyl CoA (correct)

Oxaloacetate

How many molecules of CO2 are released for every two carbons that enter the cycle?

Two (correct)

Three

Four

One

Which of the following best describes the role of the tricarboxylic acid cycle in energy metabolism?

It produces ATP directly through substrate-level phosphorylation.

It plays a key role in the oxidation of acetyl CoA. (correct)

It generates glucose from fatty acids.

It is the central pathway for amino acid catabolism.

In the context of energy metabolism, what happens to the carbon skeletons of acetyl CoA during the tricarboxylic acid cycle?

They are transformed into CO2 and energy carriers. (A) Signup and view all the answers

Which metabolic pathway is directly connected to the tricarboxylic acid cycle in terms of feeding in acetyl CoA?

Betaflexoxidation (C) Signup and view all the answers

What is the primary function of glucokinase in the liver?

To effectively remove glucose from the portal blood (B) Signup and view all the answers

Why is a high Vmax significant for glucokinase's function?

It enables glucokinase to rapidly phosphorylate glucose (A) Signup and view all the answers

How does glucokinase's activity impact glucose levels in the liver?

It leads to a lower hepatic glucose concentration by facilitating uptake (D) Signup and view all the answers

What would be the consequence of glucokinase having a low Vmax?

It would result in reduced glucose uptake in the liver (B) Signup and view all the answers

In the context of enzymatic activity, what does the term 'Vmax' refer to?

The maximum rate at which an enzyme can catalyze a reaction (B) Signup and view all the answers

What is the role of phosphofructokinase-1 (PFK-1) in glycolysis?

It is the most important control point and rate-limiting step. (C) Signup and view all the answers

Which substrate is phosphorylated by phosphofructokinase-1 (PFK-1)?

Fructose 6-phosphate (C) Signup and view all the answers

What characteristic of the reaction catalyzed by PFK-1 underscores its importance in metabolism?

It serves as a committed step in the glycolytic pathway. (A) Signup and view all the answers

Which of the following best describes the nature of the phosphorylation of fructose 6-phosphate by PFK-1?

Irreversible and the primary regulatory step in glycolysis. (B) Signup and view all the answers

What is the primary consequence of the phosphorylation of fructose 6-phosphate in glycolysis?

It leads to the production of fructose 1,6-bisphosphate, committing glucose to the glycolytic pathway. (B) Signup and view all the answers

What is the most common biochemical cause of congenital lactic acidosis?

Deficiency in E1 component of the PDH complex (A) Signup and view all the answers

Which enzyme component of the PDH complex is primarily deficient in pyruvate dehydrogenase deficiency?

E1 component (D) Signup and view all the answers

What type of acid-base disturbance is associated with pyruvate dehydrogenase deficiency?

Congenital lactic acidosis (D) Signup and view all the answers

How common is pyruvate dehydrogenase deficiency as a biochemical disorder?

It is rare. (B) Signup and view all the answers

What is the impact of pyruvate dehydrogenase deficiency on pyruvate metabolism?

Decreased conversion of pyruvate to acetyl-CoA (A) Signup and view all the answers

What role does citrate primarily serve in the TCA cycle?

It serves as an intermediate that links various metabolic pathways. (C) Signup and view all the answers

How does citrate contribute to fatty acid synthesis in the cytosol?

It supplies acetyl CoA, which is essential for fatty acid synthesis. (D) Signup and view all the answers

Which statement accurately describes the metabolic function of citrate?

Citrate serves as both an intermediate in energy production and a precursor for lipid synthesis. (C) Signup and view all the answers

What is the importance of acetyl CoA derived from citrate?

It acts as a substrate for the biosynthesis of fatty acids. (D) Signup and view all the answers

In terms of metabolic pathways, citrate has a significant role because it:

Links the carbohydrate metabolism of glycolysis with the lipid metabolism pathways. (A) Signup and view all the answers

Study Notes

Glucokinase

High Vmax allows for the liver to remove large amounts of glucose from portal blood

Phosphorylation of Fructose 6-Phosphate

Phosphofructokinase-1 (PFK-1) catalyzes the irreversible phosphorylation of fructose 6-phosphate
It is the most important control point in glycolysis and is the rate-limiting step

The Tricarboxylic Acid (TCA) Cycle

Takes place in the mitochondria and is a central pathway for energy metabolism
Two carbon units enter as acetyl CoA and two CO2 are released

Citrate

Functions as an intermediate in the TCA cycle
Provides a source of acetyl CoA for the cytosolic synthesis of fatty acids

Pyruvate dehydrogenase Deficiency

It is a rare biochemical cause of congenital lactic acidosis
Deficiency in the E1 component of the PDH complex is the most common cause

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Description

This quiz covers essential biochemical processes, focusing on glucokinase, phosphorylation of fructose 6-phosphate, and the tricarboxylic acid cycle. It also addresses pyruvate dehydrogenase deficiency and its implications. Test your knowledge on these critical metabolic pathways and their control mechanisms.