Fast Glycolysis
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Questions and Answers

During intense exercise, what stimulates glycogenolysis?

  • Increased activity of glycogen synthase
  • Epinephrine release (correct)
  • Decreased calcium release
  • Low cellular activity

Which enzyme is primarily responsible for catalyzing the process of glycogenesis?

  • Glycogen phosphorylase
  • Hexokinase
  • Glycogen synthase (correct)
  • Lactate dehydrogenase

Why does using glycogen as a substrate for glycolysis result in a net gain of one extra ATP compared to using glucose?

  • The hexokinase reaction, which consumes ATP, is bypassed (correct)
  • Glycogen directly enters the Krebs cycle, bypassing glycolysis
  • Glycogen inhibits the phosphofructokinase (PFK) reaction, saving ATP
  • Glycogen stimulates additional ATP production in oxidative phosphorylation

In glycogenolysis, what is the role of glycogen phosphorylase?

<p>It breaks down glycogen into glucose-1-phosphate (C)</p> Signup and view all the answers

Under what cellular conditions is glycogen synthase most active?

<p>Following a meal (D)</p> Signup and view all the answers

What is the immediate product resulting from glycogenolysis, which is then converted to glucose-6-phosphate (G6P)?

<p>Glucose-1-phosphate (C)</p> Signup and view all the answers

How the addition of a Pi during glycogenolysis contributes to ATP production during glycolysis?

<p>It creates a substrate that bypasses the ATP-consuming hexokinase reaction (D)</p> Signup and view all the answers

Which of the following is NOT a stimulus for glycogenolysis?

<p>Elevated levels of insulin (A)</p> Signup and view all the answers

What is the primary reason the liver utilizes glucokinase (GK) instead of hexokinase (HK) found in muscle cells?

<p>GK allows the liver to export glucose back into the bloodstream via glucose-6-phosphatase, a function not needed in muscle. (A)</p> Signup and view all the answers

Why is the phosphofructokinase (PFK) reaction considered a key regulatory step in glycolysis?

<p>It commits the cell to glycolysis, and its product is a necessary precursor for the subsequent steps. (A)</p> Signup and view all the answers

During glycolysis, aldolase splits fructose 1,6-bisphosphate (F16P) into two 3-carbon structures. What is the immediate purpose of the subsequent step 5 in glycolysis?

<p>To convert one of the 3-carbon structures into a form that can proceed through the rest of glycolysis. (A)</p> Signup and view all the answers

How does the presence of glucose-6-phosphatase in the liver support glucose homeostasis in the body?

<p>It allows the liver to release glucose into the bloodstream when blood glucose levels are low. (B)</p> Signup and view all the answers

During the energy investment phase of glycolysis, two ATP molecules are invested. At which specific steps are these ATP molecules utilized?

<p>The conversion of glucose to glucose 6-phosphate and fructose 6-phosphate to fructose 1,6-bisphosphate. (B)</p> Signup and view all the answers

During fast glycolysis, what is the net production of ATP from one glucose molecule converted to two lactate molecules?

<p>2 ATP (B)</p> Signup and view all the answers

Which of the following statements accurately describes the hexokinase reaction in fast glycolysis?

<p>It uses ATP to phosphorylate glucose, trapping it in the cell. (A)</p> Signup and view all the answers

What is the primary role of phosphoglucoisomerase in the preparatory phase of glycolysis?

<p>To convert glucose-6-phosphate into fructose-6-phosphate. (A)</p> Signup and view all the answers

Why is the conversion of glucose to glucose-6-phosphate (G6P) by hexokinase considered a coupled reaction?

<p>Because it combines an anabolic reaction (glucose to G6P) with a catabolic reaction (ATP to ADP). (D)</p> Signup and view all the answers

Which characteristic distinguishes 'fast' glycolysis from other metabolic pathways?

<p>It results in the production of lactate. (C)</p> Signup and view all the answers

In which cellular compartment does fast glycolysis primarily take place?

<p>Sarcoplasm (cytosol) (C)</p> Signup and view all the answers

Which of the following best describes the function of glucokinase, as opposed to hexokinase?

<p>It adds the phosphate in the liver. (C)</p> Signup and view all the answers

If a person has a genetic defect that impairs the function of phosphoglucoisomerase, what immediate effect would this have on glycolysis?

<p>Buildup of glucose-6-phosphate. (D)</p> Signup and view all the answers

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

<p>Adding a phosphate group to fructose-6-phosphate (F6P), forming fructose 1,6-diphosphate (FDP). (D)</p> Signup and view all the answers

Why is the reaction catalyzed by phosphofructokinase (PFK) considered a committed step in glycolysis?

<p>The reaction commits the molecule to proceed through the remaining steps of glycolysis. (B)</p> Signup and view all the answers

Which enzyme is responsible for splitting fructose 1,6-bisphosphate (FDP) into two 3-carbon molecules?

<p>Aldolase (C)</p> Signup and view all the answers

What is the significance of the conversion of dihydroxyacetone phosphate (DHAP) to glyceraldehyde-3-phosphate (G3P) in glycolysis?

<p>It allows both products of the aldolase reaction to enter the energy payoff phase. (B)</p> Signup and view all the answers

In the context of glycolysis, what is substrate-level phosphorylation?

<p>The direct transfer of a phosphate group from a high-energy substrate to ADP, forming ATP. (D)</p> Signup and view all the answers

What are the products of the glyceraldehyde-3-phosphate dehydrogenase reaction?

<p>1,3-bisphosphoglycerate (1,3-BPG) and NADH (B)</p> Signup and view all the answers

How many net ATP molecules are produced from one glucose molecule during anaerobic glycolysis?

<p>2 (C)</p> Signup and view all the answers

In anaerobic glycolysis, what is the end product of step 10, which involves Pyruvate Kinase?

<p>Lactate (B)</p> Signup and view all the answers

Flashcards

Fast Glycolysis

Rapid energy production pathway, also known as anaerobic glycolysis or the lactic acid system.

Fast Glycolysis End Products

Glucose is converted to 2 Lactate + 2 ATP.

Glycolysis Energy Investment Phase

The beginning steps of glycolysis that require ATP input.

Glycolysis Energy Production Phase

Phase where ATP is generated.

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Hexokinase Reaction

Reaction that uses ATP to add a phosphate to glucose, trapping it in the cell.

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Coupled Reaction of Hexokinase

Glucose to Glucose-6-phosphate (G6P) and ATP to ADP

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Phospho-gluco-isomerase

An enzyme that rearranges the structure of G6P into F6P.

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Isomers (Glucose & Fructose)

Same chemical formula (C6H12O6) but different shapes (hexagon vs pentagon).

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Phosphofructokinase (PFK)

Adds a second phosphate to Fructose-6-phosphate (F6P), creating Fructose-1,6-bisphosphate (F1,6P). Irreversible and commits the molecule to glycolysis.

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Glycolysis Rate-Limiting Step

The rate-limiting step is determined by regulating PFK.

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Aldolase Function

Splits Fructose-1,6-bisphosphate (F1,6P) into two 3-carbon molecules.

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Aldolase Significance

Splitting of F1,6P by aldolase leads from the energy investment to the payoff phase.

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G3P Dehydrogenase

Oxidizes Glyceraldehyde-3-phosphate (G3P) and reduces NAD+ to NADH + H+.

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1,3-DPG Kinase

Generates 2 ATP molecules via substrate-level phosphorylation.

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Pyruvate Kinase

Generates 2 ATP and 2 Pyruvate molecules.

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Net ATP from Anaerobic Glycolysis

Anaerobic glycolysis of 1 glucose molecule yields 2 net ATP.

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Hexokinase (HK)

An enzyme that phosphorylates glucose, trapping it within the cell.

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Glucose and Fructose

Intermediates with the same chemical formula (C6H12O6) but different structures.

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Aldolase

Fructose 1,6-bisphosphate gets split into two 3-carbon molecules by this enzyme.

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Step 5 of Glycolysis

Converts one of the 3-carbon molecules into its identical form, glyceraldehyde 3-phosphate (G3P).

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Glycogenesis

The synthesis of glycogen from glucose.

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Glycogen Synthase

An enzyme that stimulates glycogenesis.

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Glycogenolysis

The breakdown of glycogen to glucose.

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Glycogen Phosphorylase

An enzyme that stimulates glycogenolysis.

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Epinephrine Release

Stimulates glycogenolysis during intense activity.

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Glycogen's Extra ATP

Glycogen breakdown nets an extra ATP because it bypasses the hexokinase reaction.

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First Four Glycolysis Reactions

The first four reactions convert glucose to glyceraldehyde-3-phosphate.

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Glycogen vs Glucose (Exercise)

During exercise glycogen yields one more net ATP than glucose does.

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Study Notes

  • Fast glycolysis is stage 1
  • It involves rapid energy production.
  • Includes Anaerobic glycolysis
  • Includes the lactic acid system
  • Takes place in the sarcoplasm (cytosol)

Glycolysis Input and output

  • Glucose breaks down into 2 Lactate + 2 ATP

Glycolysis overview

  • Know steps 1-4 of glycolysis in detail
  • Know generally what is produced in steps 6, 7, and 10
  • Focus on enzyme type & side-arrow production
  • Step 10 is important to know that pyruvate is the end product

Glycolysis preparatory phase (Steps 1-4)

  • Uses 2 ATP

Hexokinase Reaction (Step 1)

  • The hexokinase reaction uses an ATP to phosphorylate glucose and trap it in the cell
  • Glucose couples with G6P, while ATP couples with ADP
  • The reaction is irreversible in muscle
  • Glucokinase adds the phosphate in the liver, while the liver also has glucose 6-phosphatase to remove it

Phospho-gluco-isomerase (Step 2)

  • Phospho-gluco-isomerase rearranges the structure to convert G6P into F6P
  • Converts it to a pentagon shape (fructose) from a hexagon shape (glucose)
  • Glucose and fructose are isomers because they have the same chemical formula (C6H12O6), but different shapes.

Phosphofructokinase (PFK) (Step 3)

  • The phosphofructokinase (PFK) adds a second phosphate to F6p to make it FDP
  • The coupled reaction is irreversible and commits it to the rest of glycolysis
  • The rate-limiting step of glycolysis determines the speed of glycolysis by regulating PFK
  • Important for fast-twitch (Type II) fibers

Aldolase (Step 4)

  • Aldolase splits FDP into two 3-C skeletons
  • PFK makes it symmetrical, so it can be split in half
  • Step 5 involves the conversion to two equal G3Ps (glyceraldehyde 3 phosphate)
  • It leads from the energy investment to the payoff phase

Anaerobic Glycolysis

  • Includes substrate-level phosphorylation or energy generation phase

G3P dehydrogenase (Step 6)

  • G3P dehydrogenase oxidizes G3P & reduces NAD+
  • NADH & H+ turns into electron transport chain or LDH

1,3 DPG kinase (Step 7)

  • 2 ATP produced

Pyruvate kinase (Step 10)

  • 2 ATP and 2 Pyruvate are produced
  • As a result, 4 total ATP and 2 NET ATP are produced from anaerobic glycolysis of glucose

Glycogen Metabolism

  • Glycogen synthase is stimulated by low cellular activity or following a meal
  • It is stored in the cytoplasm

Glycogenesis

  • Glycogen synthase

Glycogenolysis

  • Glycogen phosphorylase
  • Stimulated by high cellular activity
  • Epinephrine released during intense activity
  • Calcium released
  • Adds a Pi
  • Converted to G6P
  • Adds 1 net ATP with glycolysis

Glycogen vs Glucose Metabolism

  • An extra ATP is net when using glycogen as a substrate
  • HK reaction is bypassed, extra ATP not invested

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Related Documents

Glycolysis Slides & Notes PDF

Description

This lesson covers fast glycolysis, focusing on rapid energy production through anaerobic glycolysis and the lactic acid system. It details the inputs, outputs, and key steps, especially 1-4. Focus on enzyme types and side-arrow production, notably pyruvate as the end product of step 10.

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