Glycolysis Quiz Chapter 2
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Questions and Answers

What type of sugar transformation occurs in the reaction catalyzed by phosphohexose isomerase?

  • Fructose to Glucose
  • Glucose to Fructose
  • Ketose to Aldose
  • Aldose to Ketose (correct)

    • Which reaction represents a key regulatory step in glycolysis?

  • Glyceraldehyde-3-phosphate Reaction
  • Aldolase Reaction
  • Phosphofructokinase Reaction (correct)
  • Phosphohexose Isomerase Reaction

    • What products are formed from the splitting of Fructose 1,6-bisphosphate?

  • Glyceraldehyde-3-phosphate and Dihydroxyacetone phosphate (correct)
  • Phosphoenolpyruvate and ATP
  • Pyruvate and NADH
  • Glucose and Fructose

    • Which molecule is crucial for the oxidation step involving Glyceraldehyde 3-phosphate?

    <p>NAD+</p> Signup and view all the answers

    How many times will the reactions occur due to the presence of two 3-carbon molecules?

    <p>Twice</p> Signup and view all the answers

    What is produced during the process of substrate level phosphorylation in Reaction 7?

    <p>ATP</p> Signup and view all the answers

    What type of reaction occurs in Reaction 8?

    <p>Isomerization</p> Signup and view all the answers

    What is the product formed from 2-Phosphoglycerate in Reaction 9?

    <p>Phosphoenolpyruvate</p> Signup and view all the answers

    Which enzyme is responsible for converting 1,3-Bisphosphoglycerate to 3-Phosphoglycerate?

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

    How many molecules of ATP are produced during Reaction 7?

    <p>2</p> Signup and view all the answers

    Which reaction stage utilizes Enolase in the conversion of 2-Phosphoglycerate?

    <p>Reaction 9</p> Signup and view all the answers

    What is the overall role of ATP produced during the discussed reactions?

    <p>Energy currency of the cell</p> Signup and view all the answers

    Which of the following statements regarding Reaction 10 is true?

    <p>ATP is produced through substrate level phosphorylation.</p> Signup and view all the answers

    What is the net yield of ATP from glycolysis?

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

    What happens to pyruvate during anaerobic glycolysis?

    <p>It is converted to lactate.</p> Signup and view all the answers

    Which cofactor is regenerated when pyruvate is converted to lactate?

    <p>NAD+</p> Signup and view all the answers

    Which factor does NOT influence the regulation of glycolysis?

    <p>Temperature</p> Signup and view all the answers

    What effect does high ATP concentration have on phosphofructokinase?

    <p>Inhibits the enzyme</p> Signup and view all the answers

    Which metabolic fate of pyruvate occurs in the presence of oxygen?

    <p>It enters the citric acid cycle.</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of pyruvate to lactate?

    <p>Lactate dehydrogenase</p> Signup and view all the answers

    What happens to NADH during the conversion of pyruvate to lactate?

    <p>It is oxidized to NAD+.</p> Signup and view all the answers

    What is the primary energy yield from glycolysis?

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

    Under which conditions can glycolysis function?

    <p>Both aerobic and anaerobic conditions</p> Signup and view all the answers

    What is the main catabolic pathway using glucose present in all tissues?

    <p>Glycolysis</p> Signup and view all the answers

    Which cell type solely relies on glycolysis for ATP production due to lack of mitochondria?

    <p>Red blood cells</p> Signup and view all the answers

    What are the end products of glycolysis under anaerobic conditions?

    <p>Pyruvate and lactate</p> Signup and view all the answers

    Which process allows tumor cells to generate energy preferentially?

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

    Which type of tissue is specifically highlighted for needing ATP quickly during intense exercise?

    <p>Skeletal muscle</p> Signup and view all the answers

    What major source of ATP cannot utilize fats as an energy source?

    <p>Red blood cells</p> Signup and view all the answers

    What is the primary function of glycolysis in the body?

    <p>ATP synthesis</p> Signup and view all the answers

    Which enzyme is responsible for the conversion of glucose to glucose 6-phosphate?

    <p>Hexokinase</p> Signup and view all the answers

    During glycolysis, how many ATP molecules are consumed in the activation stage?

    <p>2</p> Signup and view all the answers

    What is the final product of glycolysis under anaerobic conditions?

    <p>Lactate</p> Signup and view all the answers

    Which enzyme's activity is inhibited by glucose-6-phosphate, indicating a regulatory mechanism in glycolysis?

    <p>Hexokinase</p> Signup and view all the answers

    What is the significance of lactate dehydrogenase in muscle metabolism?

    <p>It regenerates NAD+</p> Signup and view all the answers

    Which of the following statements is true regarding glucokinase?

    <p>Has a higher Km than hexokinase</p> Signup and view all the answers

    In glycolysis, the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate is catalyzed by which enzyme?

    <p>Phosphofructokinase</p> Signup and view all the answers

    What are the products of one glucose molecule at the end of glycolysis?

    <p>2 ATP and 2 pyruvate</p> Signup and view all the answers

    What is meant by substrate-level phosphorylation during glycolysis?

    <p>Direct synthesis of ATP from ADP using energy from glucose</p> Signup and view all the answers

    Which metabolic pathway provides an immediate source of glucose for glycolysis?

    <p>Glycogenolysis</p> Signup and view all the answers

    Which stage in glycolysis involves the splitting of glucose into two three-carbon molecules?

    <p>Cleavage stage</p> Signup and view all the answers

    What role does NAD+ play in the process of glycolysis?

    <p>It serves as an electron carrier</p> Signup and view all the answers

    Study Notes

    Glucose Metabolism: Glycolysis & Anaerobic Metabolism

    • Lecture Focus: Glucose metabolism, specifically glycolysis and anaerobic metabolism
    • Lecturer: Dr. Lauren Albee
    • Department: Biochemistry
    • Resources: Biochemistry and Molecular Biology Chapters 11 (pp. 181-187) and 13 (pp. 210-215). Available as an e-textbook at https://bibliu.com/app/#/signinPage
    • Learning Outcomes: Students should be able to:
      • Draw the structures of glucose and glycogen
      • Outline the metabolic events in glucose conversion to pyruvate
      • Explain ATP formation from ADP via substrate-level phosphorylation
      • Describe NAD+ regeneration from NADH under aerobic and anaerobic conditions, including the role of lactate dehydrogenase
      • Provide an example of a control mechanism in glycolysis regulation
      • Summarize the roles of glycolysis across different tissues (e.g., red blood cells)

    Structure and Function of Glucose and Glycogen

    • Glucose:
      • Monosaccharide
      • Approximately 10 g in plasma
      • Osmotically active
      • Immediate energy source (glycolysis)
      • Synthesized from non-carbohydrate sources (gluconeogenesis)
    • Glycogen:
      • Polysaccharide
      • Approximately 400 g in tissue stores
      • Low osmolarity
      • Medium-term fuel source
      • Synthesis and breakdown later discussed

    Glycolysis: Key Points

    • Definition: Glucose (C6) to pyruvate (C3)
    • Location: Cytosol (10 soluble enzymes)
    • Tissues: All tissues
    • Functions: Energy trapping (ATP synthesis); intermediates for fat and amino acid synthesis

    Sources of Glucose for Glycolysis

    • Sugars and starches from the diet
    • Breakdown of stored glycogen from the liver
    • Recycled glucose (from lactic acid, amino acids, or glycerol)

    Glycolysis: Summary Diagram

    • The diagram illustrates the ten reactions of glycolysis, featuring key enzymes, intermediates, and ATP/ADP transformations. Glycolysis is depicted as a sequence of enzymatic reactions involving glucose, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate, and other intermediates ultimately leading to the production of pyruvate.

    Glycolysis: Stages

    • Activation (using ATP): Converting glucose to fructose-1,6-bisphosphate, requiring ATP.
    • Splitting the 6-carbon sugar: Breaking the 6-carbon sugar into two 3-carbon sugars, yielding glyceraldehyde-3-phosphate.
    • Oxidation (removing 2H atoms): Oxidizing glyceraldehyde-3-phosphate, creating NADH and generating energy.
    • Synthesis of ATP: Generating ATP through substrate-level phosphorylation.

    Reactions 1, 2 &3 (activation stage)

    • Reaction 1: Hexokinase or glucokinase phosphorylates glucose to glucose-6-phosphate, trapping it in the cell.
    • Reaction 2: Phosphohexose isomerase converts glucose-6-phosphate to fructose-6-phosphate.
    • Reaction 3: Phosphofructokinase phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate, a crucial regulatory step.

    Splitting of 6C Sugar to 3C Units

    • Aldolase breaks fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate.

    Reactions 4 & 5

    • Aldolase catalyzes the cleavage of fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP).
    • Triose phosphate isomerase quickly converts DHAP into G3P.

    Oxidation Step (Reaction 6)

    • Glyceraldehyde-3-phosphate dehydrogenase oxidizes glyceraldehyde-3-phosphate, producing NADH and 1,3-bisphosphoglycerate.
    • This reaction marks an oxidative process vital for energy generation in glycolysis.

    ATP Synthesis Stages (Reactions 7, 8, 9, 10)

    • Reaction 7: Phosphoglycerate kinase produces ATP from 1,3-bisphosphoglycerate.
    • Reaction 8: Phosphoglycerate mutase converts 3-phosphoglycerate to 2-phosphoglycerate.
    • Reaction 9: Enolase transforms 2-phosphoglycerate into phosphoenolpyruvate (PEP).
    • Reaction 10: Pyruvate kinase converts PEP to pyruvate, creating a second ATP molecule.

    Reaction 7 - Substrate Level Phosphorylation

    • ATP is produced during this step through substrate-level phosphorylation.
    • Two ATP molecules are produced for each glucose molecule.

    Reaction 8 - Isomerisation

    • Phosphoglycerate mutase moves the phosphate group within the substrate, maintaining the pathway.
    • This reversible reaction moves a phosphate group, altering the configuration.

    Reaction 9

    • Enolase catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate by removing water molecules.
    • The molecule is dehydrate to form phosphoenolpyruvate (PEP), an important link between glycolysis and other metabolic processes.

    Reaction 10 - Substrate Level Phosphorylation

    • Pyruvate kinase generates a second ATP molecule through substrate-level phosphorylation.
    • It converts phosphoenolpyruvate (PEP) to pyruvate, releasing energy with the formation of ATP.
    • Note this step is irreversible.

    Summary Slide: ATP Yields

    • Early stages use 2 ATP
    • Later stages make 4 ATP
    • Net yield = 2 ATP (plus further ATP from mitochondrial metabolism)

    Anaerobic Glycolysis

    • When oxygen availability is limited, pyruvate is converted to lactate.
    • This process regenerates NAD+ from NADH, enabling glycolysis to continue without oxygen.
    • The production of lactate during anaerobic conditions supports the regeneration of (oxidized) NAD+, essential for continuing glycolysis.

    Reaction Catalyzed by Lactate Dehydrogenase

    • Lactate dehydrogenase is a reversible enzyme.
    • It converts pyruvate to lactate when oxygen is limited, using NADH, releasing energy for the continuation of glycolysis.

    Metabolic Fates of Pyruvate

    • In the absence of oxygen or mitochondria, pyruvate can be converted into lactate or ethanol.
    • When sufficient oxygen and mitochondria are present, pyruvate can enter the citric acid cycle, producing ATP.

    Regulation of Glycolysis

    • Controlled by allosteric and hormonal mechanisms.
    • One example of allosteric regulation: Phosphofructokinase regulation (ATP effects on the enzyme).

    Allosteric Inhibition of Phosphofructokinase by ATP

    • ATP binding to a regulatory site on the enzyme slows the reaction.
    • This is a control mechanism, ensuring that glycolysis is suppressed when sufficient ATP is available.

    Specialised Functions in Tissues

    • Skeletal muscle: Rapid ATP production during intense exercise.
    • Red blood cells: Primary pathway for ATP generation. (No mitochondria)
    • Brain: Major energy source for ATP, but it cannot utilize fats as energy sources.

    Summary of Glycolysis

    • Main catabolic pathway for glucose utilization across all cells.
    • Primarily anaerobic, a second ATP production in aerobic conditions.
    • Low energy yield (2 ATP) but a crucial pathway, with generated pyruvate entering mitochondria for more significant ATP production.
    • Production of intermediates for fatty acid and other metabolic processes.

    Discoveries and Dilemmas

    • Relevant 'extras' for further consideration, not required for immediate learning.

    The Warburg Effect

    • Tumour cells show high glycolytic rates, even with functional mitochondria.
    • This is a hallmark feature of cancerous growth and is being intensively studied for diagnostic and therapeutic purposes.

    Multiple Choice Questions (MCQs)

    • Questions related to glycolysis products, relevant cell types, and ATP yields are presented. See pages 35-38 for the specific MCQ questions.

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    Description

    Test your knowledge on glycolysis with this quiz focusing on key concepts and reactions, such as sugar transformations, regulatory steps, and important molecules involved. Perfect for students studying biochemistry or related fields.

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