Glycolysis Overview Quiz

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Questions and Answers

What is the main function of the glycolytic pathway?

  • Break down glucose to provide energy and intermediates (correct)
  • Store energy in the form of glycogen
  • Synthesize glucose from non-carbohydrate sources
  • Convert pyruvate to fatty acids

Under which conditions can glycolysis occur?

  • Only aerobic conditions
  • Both aerobic and anaerobic conditions (correct)
  • Only anaerobic conditions
  • Only in the presence of insulin

What is the initial substrate for the glycolytic pathway?

  • D-glucose (correct)
  • Acetyl CoA
  • Pyruvate
  • D-fructose

Where does glycolysis primarily take place within the cell?

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

What is the final product of glycolysis under aerobic conditions?

<p>Pyruvate (D)</p> Signup and view all the answers

Which organ primarily stores glycogen generated from glycolysis?

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

What are the by-products of glycolysis under anaerobic conditions?

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

What metabolic pathway is activated during the fed state to support glycolysis?

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

Which enzyme is responsible for substrate level phosphorylation in glycolysis?

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

What is the main purpose of phosphorylating glucose in the first step of glycolysis?

<p>To trap glucose in the cell (C)</p> Signup and view all the answers

Which of the following kinases is reversible in the glycolytic pathway?

<p>Phosphoglycerate kinase (A)</p> Signup and view all the answers

What role does Mg2+ play in the function of kinases during glycolysis?

<p>It acts as a metal cofactor for ATP utilization (C)</p> Signup and view all the answers

What is produced as a result of the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

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

What inhibits the enzyme enolase, affecting the glycolytic pathway?

<p>Sodium fluoride (A)</p> Signup and view all the answers

What is the product of anaerobic glycolysis when pyruvate is reduced?

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

How does NADH reoxidization affect glycolysis under anaerobic conditions?

<p>It allows glycolysis to continue (C)</p> Signup and view all the answers

What is the primary end product of anaerobic glycolysis?

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

How many steps are involved in aerobic glycolysis?

<p>10 steps (D)</p> Signup and view all the answers

Which of the following can occur in cells lacking adequate oxygen supply?

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

What is the net ATP yield from anaerobic glycolysis?

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

Which enzyme catalyzes one of the irreversible steps in glycolysis?

<p>Phosphofructokinase-1 (A), Hexokinase (C)</p> Signup and view all the answers

What is the main difference in the final end products of aerobic versus anaerobic glycolysis?

<p>Aerobic produces pyruvate, anaerobic produces lactate (D)</p> Signup and view all the answers

Which metabolic pathway occurs under intensive exercise in skeletal muscles?

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

What is the net equation for anaerobic glycolysis?

<p>D-glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 lactate + 2 ATP (B)</p> Signup and view all the answers

During which step of glycolysis is the conversion of D-glucose to glucose-6-phosphate catalyzed?

<p>Hexokinase reaction (D)</p> Signup and view all the answers

Which component is not generated during aerobic glycolysis?

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

Flashcards

Aerobic Glycolysis

Glycolysis occurring in cells with mitochondria and adequate oxygen, producing pyruvate and 8 ATP.

Anaerobic Glycolysis

Glycolysis in cells lacking mitochondria or oxygen, producing lactate and 2 ATP.

Pyruvate

End product of aerobic glycolysis.

Lactate

End product of anaerobic glycolysis.

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Irreversible Steps (Glycolysis)

The 3 steps in glycolysis that cannot be reversed: Hexokinase/Glucokinase, PFK-1, and Pyruvate Kinase .

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Kinases in Glycolysis

The 4 enzymes catalyzing phosphorylation reactions in glycolysis. 3 are irreversible, and phosphoglycerate kinase is the only reversible one.

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Substrate-Level Phosphorylation

Production of ATP directly during glycolysis, catalyzed by Phosphoglycerate kinase and Pyruvate kinase.

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NADH Production (Glycolysis)

Glyceraldehyde 3-phosphate dehydrogenase catalyzes the reaction producing NADH.

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Glucose Trapping

Phosphorylation converts glucose to glucose-6-phosphate, preventing its exit from the cell.

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Glucose Activation

Phosphorylation activates glucose, enabling its glycolytic pathway.

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Magnesium Cofactor

Magnesium (Mg2+) is a cofactor essential for many kinases, particularly those in glycolysis.

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Fluoride Inhibitor

Fluoride inhibits the enzyme enolase, reducing dental caries.

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Hexokinase/Glucokinase

Enzyme responsible for the first irreversible step in glycolysis.

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Phosphofructokinase-1 (PFK-1)

Enzyme responsible for a crucial irreversible step in glycolysis.

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Glyceraldehyde 3-Phosphate Dehydrogenase

Enzyme catalyzing the reaction producing NADH in glycolysis.

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Pyruvate Kinase

Enzyme catalyzing a substrate-level phosphorylation in the final step of glycolysis.

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Lactate Dehydrogenase (LDH)

Enzyme responsible for converting pyruvate to lactate in anaerobic glycolysis.

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Step 11 (Anaerobic Glycolysis)

Lactate dehydrogenase reduces pyruvate to lactate, reoxidizing NADH to NAD+.

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Study Notes

Types of Glycolysis

  • Aerobic glycolysis occurs in cells with mitochondria and an adequate oxygen supply.
  • Anaerobic glycolysis occurs in cells lacking mitochondria, cells that are poorly vascularized, or cells deprived of sufficient oxygen.
  • Aerobic glycolysis has 10 steps and produces pyruvate as the end product.
  • Anaerobic glycolysis has 11 steps and produces lactate as the end product.
  • Aerobic glycolysis produces 8 ATP, while anaerobic glycolysis produces 2 ATP.

Notes on Glycolysis

  • Irreversible steps: There are 3 irreversible steps in glycolysis: hexokinase/glucokinase, PFK-1, and pyruvate kinase.
  • Kinases: There are 4 kinases in glycolysis, 3 are irreversible, and phosphoglycerate kinase is the only reversible kinase.
  • Substrate Level Phosphorylation: There are 2 substrate-level phosphorylation reactions catalyzed by phosphoglycerate kinase and pyruvate kinase.
  • NADH Production: Glyceraldehyde 3-phosphate dehydrogenase catalyzes a reaction that produces NADH.
  • Glucose Trapping: The first step of glycolysis, phosphorylation, traps glucose inside the cell by converting it to glucose 6-phosphate, a negatively charged molecule that cannot cross the cell membrane.
  • Glucose Activation: Phosphorylation also activates glucose to proceed through the glycolytic pathway.
  • Magnesium Cofactor: Magnesium (Mg2+) is a metal cofactor for kinases and ATP is complexed with Mg2+ during this process.
  • Fluoride Inhibitor: Fluoride inhibits the enzyme enolase, reducing dental caries.

Exercise

  • Enzyme X1 is Hexokinase/Glucokinase.
  • Enzyme X2 is Phosphofructokinase-1 (PFK-1).
  • Enzyme X3 is Glyceraldehyde 3-Phosphate Dehydrogenase.
  • Enzyme X4 is Pyruvate Kinase.
  • The inhibitor (I) of enzyme X4 is Fluoride.

Anaerobic Glycolysis

  • Step 11: Lactate dehydrogenase (LDH) reduces pyruvate to lactate.
  • LDH's Role: LDH reoxidizes NADH to NAD+, allowing glycolysis to proceed under anaerobic conditions.
  • Pyruvate Reduction: Pyruvate is reduced to lactate during this step.
  • No ATP Production: No ATP is formed from NADH during anaerobic glycolysis.

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