Regulation of Glycolysis Enzymes

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Questions and Answers

What is the role of glucose-6-P in regulating glycogen synthesis?

It acts as a stimulator (correct)

It is only involved in glycogenolysis

It has no effect

It acts as an inhibitor

What is the effect of high blood glucose levels on glycogen synthesis in the liver?

It has no effect

It inhibits glycogen synthesis (correct)

It stimulates glycogen synthesis

It only affects glycogenolysis

What is the role of protein kinase A in regulating glycogen metabolism?

It phosphorylates glycogen synthase, activating it

It phosphorylates phosphorylase kinase, activating it (correct)

It has no role in glycogen metabolism

It phosphorylates glycogen phosphorylase, activating it

What stimulates hexokinase?

Insulin Signup and view all the answers

What is the effect of insulin on glycogen synthesis?

It stimulates glycogen synthesis Signup and view all the answers

What inhibits hexokinase?

Glucose-6-P Signup and view all the answers

What is the role of calcium ions in regulating glycogen metabolism?

They stimulate glycogenolysis only in muscles Signup and view all the answers

What is the effect of AMP on glycogen metabolism?

It stimulates glycogenolysis Signup and view all the answers

What stimulates glucokinase?

Glucose Signup and view all the answers

What stimulates phosphofructokinase-1?

All of the above Signup and view all the answers

What is the role of glycogen phosphorylase in glycogen metabolism?

It breaks down glycogen into glucose-1-phosphate Signup and view all the answers

What inhibits glucokinase?

Fructose-6-P Signup and view all the answers

What is the effect of epinephrine and glucagon on glycogen metabolism?

They stimulate glycogenolysis Signup and view all the answers

What is the committed step of glycolysis?

Fructose 6-phosphate converted into fructose 1,6-bisphosphate Signup and view all the answers

What is the fate of pyruvate in anaerobic conditions?

Converted into lactate Signup and view all the answers

What are the rate-limiting steps of glycolysis?

Glucose converted into glucose 6-phosphate and fructose 6-phosphate converted into fructose 1,6-bisphosphate Signup and view all the answers

What is the fate of pyruvate in aerobic conditions?

Converted into acetyl-CoA Signup and view all the answers

What stimulates phosphofructokinase-2?

All of the above Signup and view all the answers

What is the effect of citrate on PFK-1?

It inhibits PFK-1 Signup and view all the answers

Which of the following inhibits pyruvate kinase?

Acetyl-CoA and ATP Signup and view all the answers

What is the effect of glucagon on PFK-2?

It phosphorylates and inhibits PFK-2 Signup and view all the answers

What is the product of anaerobic glycolysis?

Lactate Signup and view all the answers

What is the effect of increased NADH/H+ on anaerobic glycolysis?

It stimulates anaerobic glycolysis Signup and view all the answers

What is the purpose of buffer systems in the body?

To maintain blood pH levels Signup and view all the answers

What is the effect of ATP on PFK-1?

It inhibits PFK-1 Signup and view all the answers

What is the effect of insulin on pyruvate kinase?

It stimulates pyruvate kinase Signup and view all the answers

Study Notes

Protein Digestion and Absorption

Pepsin:
- An endopeptidase active at pH 1-2
- Cleaves peptide bonds after aromatic AAs from N-terminus
Pancreatic peptidases:
- Endopeptidases: trypsin, chymotrypsin (cleaves aromatic AAs), and elastase (cleaves small AAs)
- Important for protein digestion and absorption

Carbohydrate Metabolism

Glycolysis

The full oxidation of glucose yields a significant amount of energy
A catabolic process converting glucose to pyruvate via many enzymes
Takes place in the cytosol of every cell, especially in the brain and muscles
Divided into two phases: preparatory and payoff phases
Preparatory phase: glucose => glyceraldehyde 3-phosphate + dihydroxyacetone phosphate
Committed step: fructose 6-phosphate converted into fructose 1,6-bisphosphate
Payoff phase: glyceraldehyde 3-phosphate + dihydroxyacetone phosphate converted into pyruvate
Rate-limiting steps: glucose converted into glucose 6-phosphate by hexokinase, and fructose 6-phosphate converted into fructose 1,6-bisphosphate by phosphofructokinase-1
Energy-yielding steps: glyceraldehyde-3-P oxidation, ATP synthesis by phosphoglycerate kinase, and ATP synthesis in the last step of glycolysis
Fate of pyruvate: converted into acetyl-CoA in aerobic conditions, and into lactate in anaerobic conditions
Regulation of glycolysis: hexokinase, glucokinase, and phosphofructokinase-1 are regulated by various molecules, including insulin, glucose, and ATP

Gluconeogenesis

The synthesis of glucose from non-carbohydrate precursors
Takes place primarily in the liver and to a small extent in the renal cortex and enterocytes
Follows the same pathway as glycolysis, except for reversible reactions and no ATP generation
Animals can produce glucose from lactate, amino acids, and glycerol

Glycogen Metabolism

Place of action: primarily in the liver and muscles, in the cytosol
Function of glycogen in muscles: energy source
Function of glycogen in liver: regulates blood glucose levels
Glycogenesis: making glycogen from glucose
Glycogenolysis: breakdown of glycogen for quick energy release
Regulation of glycogen synthesis and degradation: glycogen phosphorylase and glycogen synthase are regulated by allosteric and hormonal mechanisms

Anaerobic Glycolysis and Buffer Systems

Anaerobic glycolysis = lactic acid fermentation
Reduction of pyruvate into lactate under anaerobic conditions
Occurs in vigorously contracting muscles and erythrocytes
Lactate levels are a predictor for cancer patient survival
Regulation of anaerobic glycolysis: stimulated by increased NADH/H+, anaerobic conditions, and breakdown of ethanol; inhibited by high lactate levels
Buffer systems maintain blood pH levels
Acidosis: blood pH < 7.45
Hemoglobin buffer system deals with O2 and CO2 levels in erythrocytes

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Description

This quiz covers the regulation of glycolysis enzymes, including PFK-1 and Pyruvate kinase, by various molecules such as ATP, PEP, citrate, glucagon, and alanine.