Carbs checklist Quiz1
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Questions and Answers

What is the function of NADH and FADH2 in the cell?

  • They catalyze protein synthesis
  • They act as energy carriers through redox reactions (correct)
  • They regulate cell division
  • They store genetic information

    • Why are NADH and FADH2 considered energetic molecules?

  • Because they contain a large number of phosphate groups
  • Because they have high ATP content
  • Because they have high reduction potential and carry low-energy electrons
  • Because they have low reduction potential and carry high-energy electrons (correct)

    • In glycolysis, how many ATP molecules are invested initially for each molecule of glucose?

  • 6 ATP molecules
  • 8 ATP molecules
  • 2 ATP molecules (correct)
  • 4 ATP molecules

    • During the 'pay off phase' of glycolysis, how many ATP molecules are released per glyceraldehyde molecule?

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

    What is the net gain of ATP molecules per molecule of glucose that follows the glycolytic pathway?

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

    Why is the priming phase of glycolysis named as such?

    <p>Because it requires an input of energy in the form of ATP (C)</p> Signup and view all the answers

    What is the primary function of the coenzyme FAD in cellular metabolism?

    <p>Acting as an electron acceptor in catabolic processes (D)</p> Signup and view all the answers

    In response to the need for ribose-5-phosphate, how does the flux through the pentose phosphate pathway change?

    <p>The flux is diverted towards the non-oxidative phase (A)</p> Signup and view all the answers

    What is the advantage of glycogen's branched structure?

    <p>Facilitates rapid and efficient breakdown and synthesis of glycogen (D)</p> Signup and view all the answers

    Which enzymes are involved in glycogen degradation?

    <p>Glycogen phosphorylase, glycogen debranching enzyme, phosphoglucomutase (B)</p> Signup and view all the answers

    What activates glycogen phosphorylase?

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

    How does phosphorylation affect the activity of glycogen phosphorylase?

    <p>It converts it to the more active form (D)</p> Signup and view all the answers

    What is the primary purpose of the dehydration of 2-phosphoglycerate in glycolysis?

    <p>To form a high-energy enol intermediate, phosphoenolpyruvate (PEP) (B)</p> Signup and view all the answers

    How does glycolysis utilize the chemical coupling of endergonic and exergonic reactions to generate ATP?

    <p>By generating high-energy compounds that undergo substrate-level phosphorylation (C)</p> Signup and view all the answers

    Which products of glycolysis are reduced molecules that the cell can oxidize to recover free energy?

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

    What are the three possible fates of pyruvate?

    <p>Conversion to acetyl-CoA, conversion to lactate, and conversion to CO2 (D)</p> Signup and view all the answers

    In which type of fermentation is pyruvate converted into lactate?

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

    What is the role of TPP in glycolysis?

    <p>To catalyze the decarboxylation of pyruvate (C)</p> Signup and view all the answers

    What is the net ATP yield per glucose molecule in anaerobic degradation?

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

    Which process has a higher production rate, anaerobic or aerobic degradation of glucose?

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

    What are the potential control points in glycolysis?

    <p>Hexokinase, phosphofructokinase-1 (PFK-1), and pyruvate kinase (B)</p> Signup and view all the answers

    What are the allosteric inhibitors of PFK-1?

    <p>High levels of ATP and citrate (D)</p> Signup and view all the answers

    How is PFK-1 activity regulated by phosphorylation?

    <p>Phosphorylation decreases enzyme activity (A)</p> Signup and view all the answers

    Why is ATP not an effective allosteric regulator of enzyme activity?

    <p>It is too abundant in cells to have a regulatory effect (A)</p> Signup and view all the answers

    What is the metabolic advantage of a substrate cycle?

    <p>It provides a means of fine-tuning metabolic intermediates (A)</p> Signup and view all the answers

    How does fructose enter the glycolytic pathway?

    <p>Through the action of fructokinase (A)</p> Signup and view all the answers

    What is the net equation for the pentose phosphate pathway?

    <p>Glucose-6-phosphate + 2NADP+ + H2O → ribulose-5-phosphate + CO2 + 2NADPH + 2H+ (B)</p> Signup and view all the answers

    Summarize the reactions of each stage of the pentose phosphate pathway.

    <p>The oxidative phase involves reversible interconversions of sugar phosphate intermediates. (C)</p> Signup and view all the answers

    How do the transketolase and transaldolase reactions differ?

    <p>The transketolase reaction transfers a two-carbon fragment, while the transaldolase reaction transfers a three-carbon fragment. (B)</p> Signup and view all the answers

    What is the free energy source for glycogen synthesis?

    <p>Uridine triphosphate (UTP) (B)</p> Signup and view all the answers

    Describe the role of glycogenin.

    <p>It catalyzes the formation of initial glucose residues for glycogen synthesis. (B)</p> Signup and view all the answers

    Summarize the effects of AMP and G6P on glycogen phosphorylase and glycogen synthase.

    <p>AMP activates glycogen phosphorylase and inhibits glycogen synthase. (B)</p> Signup and view all the answers

    Summarize the effects of phosphorylation and dephosphorylation on glycogen phosphorylase and glycogen synthase.

    <p>Phosphorylation activates glycogen phosphorylase and inhibits glycogen synthase. (A)</p> Signup and view all the answers

    Why does a phosphorylation/dephosphorylation system allow more sensitive regulation of a metabolic process than a simple allosteric system?

    <p>It allows for fine-tuned control and rapid response to changes in cellular conditions. (C)</p> Signup and view all the answers

    How does regulation of glycogen metabolism differ between liver and muscle?

    <p>It is regulated by hormones in the liver and by exercise in muscle. (C)</p> Signup and view all the answers

    Summarize the effects of insulin, glucagon, and epinephrine on glycogen metabolism.

    <p>Insulin stimulates glycogen synthesis and inhibits glycogen breakdown, while glucagon and epinephrine stimulate glycogen breakdown. (D)</p> Signup and view all the answers

    What are the intracellular effects of cAMP and Ca2+?

    <p>cAMP activates protein kinase A (PKA), while Ca2+ can have various intracellular effects depending on the target proteins involved. (B)</p> Signup and view all the answers

    What are the substrates for gluconeogenesis?

    <p>Lactate, glycerol, amino acids, and citric acid cycle intermediates (D)</p> Signup and view all the answers

    What role do fatty acids play in gluconeogenesis?

    <p>Provide a source of acetyl-CoA for gluconeogenesis (C)</p> Signup and view all the answers

    Which reactions are not shared with glycolysis?

    <p>Pyruvate carboxylase, phosphoenolpyruvate carboxykinase, and fructose-1,6-bisphosphatase (A)</p> Signup and view all the answers

    Why is the malate–aspartate shuttle system important for gluconeogenesis?

    <p>It allows for the recycling of NADH between cytoplasm and mitochondria to generate ATP for gluconeogenesis. (D)</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of fructose-1,6-bisphosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate in glycolysis?

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

    During glycolysis, what is the role of phosphoglycerate kinase?

    <p>Catalyzes the conversion of 3-phosphoglycerate to 2-phosphoglycerate (C)</p> Signup and view all the answers

    Why does triose phosphate isomerase achieve the designation of being catalytically perfect?

    <p>It proceeds through the transition state with a rate enhancement near the diffusion limit (B)</p> Signup and view all the answers

    What type of catalytic mechanism involves the transfer of a proton between an enzyme and the substrate, altering the substrate's reactivity?

    <p>Acid-base catalysis (B)</p> Signup and view all the answers

    Which compound with high phosphate group-transfer potential is synthesized during glycolysis and yields ATP through substrate-level phosphorylation?

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

    What is the role of NADH generation during glycolysis?

    <p>To conserve energy and reducing power in the form of NADH (D)</p> Signup and view all the answers

    Which enzyme requires the cofactor NAD+ for its oxidation reaction in glycolysis?

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

    What is the chemical logic behind converting glucose to fructose before aldolase splits the sugar in two during glycolysis?

    <p>To ensure precise and controlled cleavage by aldolase (C)</p> Signup and view all the answers

    What is the role of metal-ion catalysis in glycolytic enzymes?

    <p>Assists in substrate binding or participates in the reaction mechanism (D)</p> Signup and view all the answers

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