Metabolic Pathways and Catabolic Reactions

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Questions and Answers

What is the enzyme responsible for converting fructose 1,6-bisphosphate to fructose 6-phosphate?

Phosphofructokinase-2

Fructokinase

Fructose 2,6-bisphosphatase (correct)

Phosphofructokinase-1

What is the purpose of the reciprocal actions of fructose 2,6-bisphosphate on glycolysis and gluconeogenesis?

To prevent a futile cycle (correct)

To increase ATP production

To inhibit gluconeogenesis

To activate glycolysis

What is the net result of the reciprocal actions of fructose 2,6-bisphosphate?

Prevention of a futile cycle (correct)

Decreased glucose utilization

Stimulation of glycogen synthesis

Increased glucose production

What is the role of citrate in the regulation of glycolysis and gluconeogenesis?

Inhibits phosphofructokinase-1 Signup and view all the answers

What is the effect of high ATP levels on phosphofructokinase-1?

Inhibition Signup and view all the answers

What is the effect of high AMP levels on phosphofructokinase-1?

Activation Signup and view all the answers

What is the full form of GDP?

Guanosine diphosphate Signup and view all the answers

What is the function of cAMP phosphodiesterase?

To hydrolyze cAMP to 5'-AMP Signup and view all the answers

What is the role of 5'-AMP in cellular signaling?

It is not an intracellular signaling molecule Signup and view all the answers

What happens to the effects of neurotransmitter- or hormone-mediated increases of cAMP when the extracellular signal is removed?

They are rapidly terminated Signup and view all the answers

What is the full form of cAMP?

Cyclic adenosine monophosphate Signup and view all the answers

What is the relationship between cAMP and GTP?

cAMP and GTP are structurally similar Signup and view all the answers

What is the primary function of catabolic reactions?

To capture chemical energy in the form of ATP Signup and view all the answers

What is the result of a pathway being blocked, for example, by a drug or an inherited deficiency of an enzyme?

A decrease in the flow of intermediate molecules Signup and view all the answers

What is the role of molecules in the diet or stored in cells in catabolic pathways?

They are converted into building blocks needed for the synthesis of complex molecules Signup and view all the answers

What is the purpose of repeatedly featuring pathways in the major metabolic maps?

To depict the effect of blocking a pathway on the flow of intermediate molecules Signup and view all the answers

What is the molecule that captures chemical energy in catabolic reactions?

ATP (Adenosine Triphosphate) Signup and view all the answers

What is the ultimate goal of energy generation by catabolic pathways?

To store energy in the form of ATP Signup and view all the answers

What is the first oxidation-reduction reaction of glycolysis?

Conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate Signup and view all the answers

What is the product of the first oxidation-reduction reaction of glycolysis?

1,3-bisphosphoglycerate Signup and view all the answers

Why is the reoxidation of NADH to NAD+ necessary?

To continue glycolysis Signup and view all the answers

What is the byproduct of the first oxidation-reduction reaction of glycolysis?

NADH + H+ Signup and view all the answers

What are the two major mechanisms for oxidizing NADH?

NADH-linked conversion of pyruvate to lactate and oxidation of NADH via the respiratory chain Signup and view all the answers

What is the purpose of oxidizing NADH?

To continue glycolysis Signup and view all the answers

What is the reactant of the first oxidation-reduction reaction of glycolysis?

Glyceraldehyde 3-phosphate Signup and view all the answers

What is the enzyme responsible for the first oxidation-reduction reaction of glycolysis?

Glyceraldehyde 3-phosphate dehydrogenase Signup and view all the answers

What is the byproduct of the oxidation of the aldehyde group of glyceraldehyde 3-phosphate?

Carboxyl group Signup and view all the answers

What is the function of the high-energy phosphate group at carbon 1 of 1,3-BPG?

To drive the synthesis of ATP Signup and view all the answers

What is the result of the oxidation of glyceraldehyde 3-phosphate?

The formation of a carboxyl group Signup and view all the answers

What is the role of phosphatase in glycolysis?

To remove phosphate groups from substrates Signup and view all the answers

What is the energy source for the synthesis of ATP in glycolysis?

The oxidation of glyceraldehyde 3-phosphate Signup and view all the answers

What is the product of the reaction involving the attachment of Pi to the carboxyl group?

1,3-BPG Signup and view all the answers

What is the function of the mutation of glyceraldehyde 3-phosphate?

To drive the synthesis of ATP Signup and view all the answers

What is the outcome of the coupling of the oxidation of glyceraldehyde 3-phosphate with the attachment of Pi to the carboxyl group?

The synthesis of 1,3-BPG and ATP Signup and view all the answers

Study Notes

Metabolic Intermediates and Pathways

Metabolic pathways depict the effects of blocking a pathway (e.g., by a drug or inherited enzyme deficiency) on the flow of intermediates.

Catabolic Pathways

Catabolic reactions capture chemical energy from the degradation of energy-rich fuel molecules, storing it in the form of ATP (adenosine triphosphate).
Catabolism allows molecules in the diet (or nutrient molecules stored in cells) to be converted into building blocks needed for the synthesis of complex molecules.

Energy Generation

Energy is generated by catabolic pathways, which break down energy-rich molecules to produce ATP.

Regulatory Mechanisms

The effects of neurotransmitter- or hormone-mediated increases of cAMP are rapidly terminated when the extracellular signal is removed.
Fructose 2,6-bisphosphate plays a key role in regulating glycolysis and gluconeogenesis, ensuring that both pathways are not fully active at the same time.

Glycolysis

Glycolysis is a catabolic pathway that converts glucose into pyruvate.
The conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate (1,3-BPG) is the first oxidation-reduction reaction of glycolysis.
The high-energy phosphate group at carbon 1 of 1,3-BPG conserves much of the free energy produced by the oxidation of glyceraldehyde 3-phosphate.
The energy of this high-energy phosphate drives the synthesis of ATP in the next reaction of glycolysis.

Oxidation of Glyceraldehyde 3-Phosphate

The oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate is catalyzed by glyceraldehyde 3-phosphate dehydrogenase.
This reaction is the first oxidation-reduction reaction of glycolysis.
The NADH formed by this reaction must be reoxidized to NAD+ for glycolysis to continue.

NADH Reoxidation

Two major mechanisms for oxidizing NADH are:
- The NADH-linked conversion of pyruvate to lactate (anaerobic)
- Oxidation of NADH via the respiratory chain (aerobic)

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Description

This quiz covers metabolic pathways and catabolic reactions, including how they are affected when a pathway is blocked. It explores the major metabolic maps and the capture of chemical energy.