Cellular Respiration and Glycolysis
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Questions and Answers

What is the primary function of glycolysis in cellular respiration?

  • To produce lactate in the presence of oxygen.
  • To break down glucose into pyruvate. (correct)
  • To convert glucose into ATP directly.
  • To transfer pyruvate into fatty acids.

    • Which products result from the aerobic breakdown of pyruvate?

  • Acetaldehyde and NADH.
  • Glycogen and glucose.
  • Carbon dioxide and ATP. (correct)
  • Lactate and ATP.

    • How is ATP production coupled to glycolysis?

  • ATP is generated through fermentation during glycolysis.
  • ATP is synthesized through oxidative phosphorylation.
  • ATP is produced via substrate-level phosphorylation. (correct)
  • ATP does not form during glycolysis.

    • What is the net gain of ATP during glycolysis when starting with one molecule of glucose?

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

    In which phase of glycolysis does the preparatory phase occur?

    <p>First five steps.</p> Signup and view all the answers

    Why is phosphorylated intermediates important in glycolysis?

    <p>They play a crucial role in regulating the pathway.</p> Signup and view all the answers

    What happens to pyruvate in anaerobic conditions?

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

    Which type of respiration requires the presence of oxygen?

    <p>Aerobic respiration.</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate?

    <p>Glyceraldehyde 3-phosphate dehydrogenase</p> Signup and view all the answers

    What is produced when 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate?

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

    What type of reaction occurs when 2-phosphoglycerate is dehydrated by enolase?

    <p>Reversible dehydration</p> Signup and view all the answers

    During glycolysis, what is the fate of pyruvate under anaerobic conditions?

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

    Which statement is true regarding the reaction catalyzed by pyruvate kinase?

    <p>It favors the formation of ATP.</p> Signup and view all the answers

    What is the role of phosphoglycerate mutase in glycolysis?

    <p>It shifts the phosphate group from carbon 3 to carbon 2.</p> Signup and view all the answers

    Which substrate contributes to the formation of ATP during the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate?

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

    What happens to NAD+ during the conversion of pyruvate to lactate?

    <p>It is produced</p> Signup and view all the answers

    What is the state of pyruvate kinase when it is inactive?

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

    Which phase of glycolysis involves the investment of ATP?

    <p>Preparation phase</p> Signup and view all the answers

    How many ATP are formed from the oxidation of one triose phosphate during the payoff phase of glycolysis?

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

    Which enzymes are primarily regulated in the glycolytic pathway to maintain ATP levels?

    <p>Hexokinase, Phosphofructokinase-1, and Pyruvate Kinase</p> Signup and view all the answers

    What is the net result of glycolysis from one molecule of glucose?

    <p>Two molecules of pyruvate and two molecules of NADH</p> Signup and view all the answers

    What enzyme catalyzes the isomerization of glucose 6-phosphate to fructose 6-phosphate?

    <p>Phosphohexose isomerase</p> Signup and view all the answers

    Which statement accurately describes the phosphorylation of fructose 6-phosphate?

    <p>It is controlled by the availability of ATP and fructose 6-phosphate.</p> Signup and view all the answers

    What are the products of the cleavage of fructose 1,6-bisphosphate?

    <p>Glyceraldehyde 3-phosphate and dihydroxyacetone phosphate</p> Signup and view all the answers

    What must happen to dihydroxyacetone phosphate for further metabolism in glycolysis?

    <p>It must be isomerized to glyceraldehyde 3-phosphate.</p> Signup and view all the answers

    Which statement about the ATP yield in glycolysis is correct?

    <p>There is a net yield of two ATP per glucose molecule.</p> Signup and view all the answers

    During glycolysis, what does NAD+ convert into when it is reduced?

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

    Which enzyme is considered the most important control point in glycolysis?

    <p>Phosphofructokinase 1</p> Signup and view all the answers

    What role does fructose 2,6-bisphosphate have in glycolysis?

    <p>Activating phosphofructokinase 1 activity</p> Signup and view all the answers

    What is the effect of H+ ions on phosphofructokinase (PFK)?

    <p>It inhibits PFK and decreases glycolysis.</p> Signup and view all the answers

    How does fructose 2,6-bisphosphate (F-2,6-BP) affect PFK-1?

    <p>It activates PFK-1 activity.</p> Signup and view all the answers

    What role does glucagon play in the regulation of PFK-2 and FBPase2?

    <p>It inhibits PFK-2 and activates FBPase2.</p> Signup and view all the answers

    What happens to hexokinase when PFK is inhibited?

    <p>Hexokinase is inhibited by the accumulation of glucose 6-phosphate.</p> Signup and view all the answers

    What effect does insulin have on the activities of PFK-2 and FBPase2?

    <p>It dephosphorylates both enzymes, activating PFK-2 and inhibiting FBPase2.</p> Signup and view all the answers

    What condition does excessive lactate formation relate to?

    <p>Acidosis.</p> Signup and view all the answers

    Which of the following molecules can inhibit pyruvate kinase (PK)?

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

    What is the primary regulatory step unique to glycolysis?

    <p>The action of hexokinase.</p> Signup and view all the answers

    Study Notes

    Cellular Respiration

    • Is a set of metabolic reactions that take place in cells to convert chemical energy from oxygen molecules or nutrients into ATP.
    • Consists of two types: Anaerobic and Aerobic
    • Anaerobic respiration occurs in the absence of oxygen.
    • Aerobic respiration requires oxygen to generate ATP.

    Glycolysis

    • Is a pathway used by all tissues for the breakdown of glucose.
    • Glucose is metabolized to pyruvate.
    • The breakdown of glucose into pyruvate occurs in ten steps:
      • Preparatory Phase
      • Payoff Phase

    Preparatory Phase

    • Five steps are involved in the preparatory phase.
    • Glucose is converted to fructose 1,6-bisphosphate.
    • Two ATP molecules are consumed in this phase.

    Payoff Phase

    • The remaining five steps constitute the payoff phase.
    • Fructose 1,6-bisphosphate is broken down into two molecules of glyceraldehyde 3-phosphate.
    • Oxidation of glyceraldehyde 3-phosphate generates NADH and two ATP molecules per triose phosphate.

    Net Gain of ATP

    • The net gain of ATP during glycolysis is two ATP molecules per glucose molecule.

    NAD+ Role

    • NAD+ is a key coenzyme in glycolysis.
    • It picks up electrons during the oxidation of glyceraldehyde 3-phosphate, forming NADH.
    • NADH is a reducing agent that can donate electrons to other molecules.

    Regulation of Glycolysis

    • Glycolysis is tightly regulated to ensure a steady supply of ATP.
    • Key enzymes involved in regulation are Hexokinase, PFK-1, and Pyruvate Kinase.

    PFK-1 Regulation

    • PFK-1 is the most important control point of glycolysis.
    • It is activated by fructose 2,6-bisphosphate.
    • PFK-1 is also regulated by ATP and fructose 6-phosphate concentrations.

    Hexokinase Regulation

    • Hexokinase is inhibited by glucose 6-phosphate.
    • It is also affected by the concentration of the reactant (glucose) and the availability of ATP.

    Pyruvate Kinase Regulation

    • Pyruvate Kinase is inhibited by ATP, long-chain fatty acyl CoA, and Acetyl CoA.
    • It is also under hormonal regulation by Glucagon and Insulin.
    • Insulin activates pyruvate kinase by dephosphorylating it.
    • Glucagon inhibits pyruvate kinase by phosphorylating it.

    Overall Summary of Glycolysis

    • Glycolysis is a near-universal pathway for glucose breakdown to pyruvate.
    • It generates ATP, NADH, and pyruvate.
    • All ten glycolytic enzymes are located in the cytosol.

    Importance of Glycolysis

    • It is essential for energy production in all living organisms.
    • It provides the starting material for other metabolic pathways like the citric acid cycle.
    • It is a critical pathway in various cellular processes, including muscle contraction, nerve impulses, and biosynthesis.

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    Lecture 1 Glycolysis PDF

    Description

    This quiz covers the essential concepts of cellular respiration, including both anaerobic and aerobic processes. Dive into the specifics of glycolysis, exploring its two key phases: the preparatory phase and the payoff phase. Test your knowledge on how glucose is metabolized and the ATP yield from these metabolic pathways.

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