Biochem 11.1 Glycolysis Quiz
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Questions and Answers

What is the primary product of glycolysis?

  • Two molecules of pyruvate (correct)
  • Four molecules of ATP
  • Glucose 6-phosphate
  • Two molecules of NAD+

    • Which enzyme catalyzes the phosphorylation of glucose in the first step of glycolysis?

  • Hexokinase (correct)
  • Amylase
  • Phosphatase
  • ATPase

    • During the energy-investment phase of glycolysis, how many ATP molecules are consumed?

  • Two (correct)
  • One
  • Three
  • Four

    • What is the role of NAD+ in glycolysis?

    <p>To accept electrons during glucose oxidation</p> Signup and view all the answers

    What is a key characteristic of the hexokinase-catalyzed reaction in glycolysis?

    <p>It is biochemically irreversible.</p> Signup and view all the answers

    What occurs after glucose is phosphorylated by hexokinase during glycolysis?

    <p>Glucose 6-phosphate is produced.</p> Signup and view all the answers

    Which metabolic pathway occurs entirely in the cytosol of cells?

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

    What is produced as a byproduct of glucose oxidation during glycolysis?

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

    What is the primary purpose of the energy-payoff phase in glycolysis?

    <p>To produce ATP and NADH efficiently</p> Signup and view all the answers

    Which enzyme is responsible for the oxidation of glyceraldehyde 3-phosphate in glycolysis?

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

    What happens to NAD+ during the sixth step of glycolysis?

    <p>It is reduced to NADH</p> Signup and view all the answers

    How many molecules of G3P are produced at the end of the energy-investment phase?

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

    What role does inorganic phosphate (Pi) play in the oxidation of G3P?

    <p>It phosphorylates G3P</p> Signup and view all the answers

    Why is the production of NADH significant in glycolysis?

    <p>It can enter the electron transport chain to help produce ATP</p> Signup and view all the answers

    What is the result of the reactions in the energy-payoff phase in relation to the initial energy investment?

    <p>More ATP and NADH are produced than initially invested</p> Signup and view all the answers

    In metabolic terms, what does glycolysis primarily generate from one molecule of glucose after both phases?

    <p>Four molecules of ATP and two of NADH</p> Signup and view all the answers

    What is the product formed as a result of the cleavage of fructose 1,6-bisphosphate?

    <p>Dihydroxyacetone phosphate and glyceraldehyde 3-phosphate</p> Signup and view all the answers

    Which enzyme is responsible for the conversion of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate?

    <p>Triose phosphate isomerase</p> Signup and view all the answers

    What characterizes the step catalyzed by phosphofructokinase-1 in glycolysis?

    <p>It is the first committed step of glycolysis and is highly regulated.</p> Signup and view all the answers

    What is the main outcome of the energy-investment phase of glycolysis?

    <p>The conversion of one molecule of glucose to two molecules of glyceraldehyde 3-phosphate</p> Signup and view all the answers

    What type of reaction does aldolase catalyze in glycolysis?

    <p>An elimination reaction producing a double bond</p> Signup and view all the answers

    How many ATP molecules are invested in the energy-investment phase of glycolysis?

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

    What is the fate of fructose 1,6-bisphosphate after step 3 in glycolysis?

    <p>It is committed to glycolysis until converted to pyruvate.</p> Signup and view all the answers

    Which characteristic is unique to the enzyme aldolase in the context of glycolysis?

    <p>It is classified as a lyase enzyme.</p> Signup and view all the answers

    What role does phosphofructokinase-1 (PFK-1) play in glycolysis?

    <p>It catalyzes the earliest committed step of glycolysis.</p> Signup and view all the answers

    How many net ATP molecules are produced by the entire glycolytic pathway?

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

    Which metabolite can enter the glycolytic pathway without processing through hexokinase?

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

    What is the product of mannose phosphorylation by hexokinase?

    <p>Mannose 6-phosphate</p> Signup and view all the answers

    What happens to mannose 6-phosphate during glycolysis?

    <p>It is converted to fructose 6-phosphate by phosphomannose isomerase.</p> Signup and view all the answers

    Which enzyme does NOT act on mannose 6-phosphate?

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

    What distinguishes phosphoglucose isomerase from phosphomannose isomerase?

    <p>The substrates they act upon.</p> Signup and view all the answers

    What is a common feature of alternative metabolites entering glycolysis?

    <p>They can bypass certain enzymes of glycolysis.</p> Signup and view all the answers

    What is the primary purpose of lactic acid fermentation in anaerobic cells?

    <p>To regenerate NAD+ from NADH</p> Signup and view all the answers

    What characterizes the direction of the lactic acid fermentation reaction in anaerobic cells?

    <p>It favors the reduction of pyruvate to lactate</p> Signup and view all the answers

    Why can multicellular organisms like mammals utilize lactic acid fermentation to their advantage?

    <p>They transport lactate to well-oxygenated cells</p> Signup and view all the answers

    What is the first step in the alcoholic fermentation pathway?

    <p>Decarboxylation of pyruvate</p> Signup and view all the answers

    What happens to ethanol in humans regarding alcoholic fermentation?

    <p>It is further oxidized to acetaldehyde</p> Signup and view all the answers

    Which statement is true about the products of alcoholic fermentation?

    <p>CO2 is easily eliminated due to its volatility</p> Signup and view all the answers

    How do the levels of NADH affect the direction of the lactic acid fermentation reaction?

    <p>High NADH levels favor lactate formation</p> Signup and view all the answers

    What role does the enzyme pyruvate decarboxylase play in alcoholic fermentation?

    <p>It catalyzes the decarboxylation of pyruvate</p> Signup and view all the answers

    What is the main function of pyruvate kinase in glycolysis?

    <p>Transfers phosphate from PEP to ADP to form ATP</p> Signup and view all the answers

    What is the net gain of ATP from glycolysis per glucose molecule?

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

    Which of the following statements is true about the reaction catalyzed by pyruvate kinase?

    <p>It is irreversible under physiological conditions</p> Signup and view all the answers

    How many NADH molecules are produced during the energy-payoff phase of glycolysis for every glucose molecule?

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

    What is the main outcome of the energy-payoff phase of glycolysis?

    <p>Reduction of NAD+ to NADH</p> Signup and view all the answers

    Which steps of glycolysis are considered to be highly exergonic and irreversible?

    <p>Step 1, Step 3, Step 10</p> Signup and view all the answers

    What is the role of glycolysis in cellular metabolism?

    <p>It generates ATP and NADH from glucose</p> Signup and view all the answers

    How many ATP molecules does pyruvate kinase produce for each molecule of phosphoenolpyruvate (PEP)?

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

    Study Notes

    Glycolysis and Fermentation

    • Glucose is the primary fuel source for cells, providing energy and building blocks for other molecules.
    • Glucose breakdown is called catabolism, converting glucose monosaccharides into two pyruvate molecules.
    • Glycolysis is a metabolic pathway occurring in the cytosol, converting glucose into two pyruvate molecules, reducing two NAD+ molecules to NADH, and producing two net ATP.

    Energy-Investment Phase

    • Glycolysis has 10 enzyme-catalyzed reactions, divided into two phases.

    • The first five steps, collectively called the energy-investment phase, require ATP input.

    • Step 1 (hexokinase): Phosphorylates glucose to glucose-6-phosphate, irreversibly trapping glucose in the cell. This step requires ATP as a phosphate donor, catalyzed by hexokinase.

    • Step 2 (phosphoglucose isomerase): Converts glucose-6-phosphate to fructose-6-phosphate, a reversible isomerization reaction.

    • Step 3 (phosphofructokinase-1): Phosphorylates fructose-6-phosphate to fructose-1,6-bisphosphate, a highly exergonic and irreversible step. This step is critically regulated (the major point of regulation in glycolysis)

    • Step 4 (aldolase): Cleaves fructose-1,6-bisphosphate into two 3-carbon molecules, dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P).

    • Step 5 (triose phosphate isomerase): Converts DHAP into G3P, so both products of step 4 enter the subsequent steps.

    Energy-Payoff Phase

    • Steps 6-10 of glycolysis are collectively called the energy-payoff phase
    • Step 6 (glyceraldehyde-3-phosphate dehydrogenase): Oxidizes G3P, producing 1,3-bisphosphoglycerate and NADH.
    • Step 7 (phosphoglycerate kinase): Converts 1,3-bisphosphoglycerate to 3-phosphoglycerate, producing ATP via substrate-level phosphorylation.
    • Step 8 (phosphoglycerate mutase): Moves the phosphate group from the 3rd carbon to the 2nd carbon, converting 3-phosphoglycerate to 2-phosphoglycerate.
    • Step 9 (enolase): Dehydrates 2-phosphoglycerate into phosphoenolpyruvate.
    • Step 10 (pyruvate kinase): Converts phosphoenolpyruvate to pyruvate, producing ATP via substrate-level phosphorylation.

    Fermentation

    • Fermentation is an alternative pathway to aerobic respiration, used when oxygen is scarce, regenerating NAD+ from NADH.
    • Lactic acid fermentation: Pyruvate is reduced to lactate, regenerating NAD+.
    • Alcoholic fermentation: Pyruvate is decarboxylated to acetaldehyde, then reduced to ethanol, regenerating NAD+.

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    Glycolysis and Fermentation PDF

    Description

    Test your knowledge on glycolysis with this quiz that covers key steps, enzymes, and products involved in the process. Understand the energy-investment and energy-payoff phases, as well as the roles of various substrates and cofactors. Perfect for biology students looking to reinforce their learning about cellular respiration.

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