Lecture 15
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Questions and Answers

Which group is transferred when the oxygen of the nucleophile attacks the β position of ATP?

  • AMP
  • Pyrophosphoryl (correct)
  • Phosphate (—OPO32–)
  • Pyrophosphate
  • What is the cellular ATP concentration like in most cells?

  • Below equilibrium concentration
  • At equilibrium concentration
  • Usually far above equilibrium concentration (correct)
  • Dependent on the cell's type
  • Why does the hydrolysis of PhosphoEnolPyruvate (PEP) catalyzed by pyruvate kinase have a large standard free energy of hydrolysis?

  • Products being destabilized via resonance
  • Products undergoing less favorable solvation
  • Resonance stabilization and favorable solvation of the products (correct)
  • Lack of electrostatic repulsion within reactant molecules
  • What happens when the oxygen of the nucleophile attacks the α position of ATP?

    <p>More than one of the choices is correct</p> Signup and view all the answers

    What kind of group is transferred when attacking the γ position of ATP with oxygen of the nucleophile?

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

    All the factors below contribute to the large standard free energy of hydrolysis in PEP catalyzed by pyruvate kinase EXCEPT

    <p>Resonance stabilization within the reactant molecule</p> Signup and view all the answers

    What is the most highly oxidized form of carbon found in living systems?

    <p>Carbon dioxide</p> Signup and view all the answers

    In biochemical oxidation-reduction reactions, how many electrons are typically involved in transfer?

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

    What accompanies electron transfer in order to keep charges in balance?

    <p>Proton transfer</p> Signup and view all the answers

    In dehydrogenases, like lactate dehydrogenase, how does the reaction typically proceed?

    <p>Through a stepwise transfer of proton and hydride</p> Signup and view all the answers

    Which enzyme catalyzes the reaction of lactate to pyruvate in cells?

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

    Which flavin cofactor allows single or double electron transfers?

    <p>Both FAD and FMN</p> Signup and view all the answers

    What forms when FAD or FMN accepts only one hydrogen atom?

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

    What vitamin is the isoalloxazine ring of FAD and FMN derived from?

    <p>Vitamin B2</p> Signup and view all the answers

    What deficiency leads to Stomatitis?

    <p>Vitamin B2 deficiency</p> Signup and view all the answers

    Why does the hydrolysis of 1,3-bisphosphoglycerate (1,3-BPG) have a large standard free energy of hydrolysis?

    <p>The removal of 3-phosphoglyceric acid by further metabolism and formation of the ion favor the forward reaction.</p> Signup and view all the answers

    Which of the following statements about the hydrolysis of phosphocreatine (PCr) is correct?

    <p>The release of inorganic phosphate (Pi) and the resonance stabilization of creatine favor the forward reaction.</p> Signup and view all the answers

    What is the overall result of the flow of phosphoryl groups catalyzed by kinases?

    <p>It results in an overall loss of free energy under intracellular conditions.</p> Signup and view all the answers

    What is the significance of the hydrolysis of low-energy phosphate compounds?

    <p>It releases inorganic phosphate (Pi), which has a lower phosphoryl group transfer potential.</p> Signup and view all the answers

    What is the primary factor that influences the actual free-energy change (ΔG) of ATP hydrolysis, in addition to the standard free energy (ΔG°')?

    <p>Concentrations of reactants and products</p> Signup and view all the answers

    In the two-step reaction catalyzed by ATP-dependent glutamine synthetase, what is the first step?

    <p>A phosphoryl group is transferred from ATP to glutamate</p> Signup and view all the answers

    In the context of ATP hydrolysis, what is the role of the enzyme that catalyzes the reaction?

    <p>To decrease the activation energy barrier of the reaction</p> Signup and view all the answers

    What are the common redox cofactors that allow two-electron transfer in biological systems?

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

    What vitamin is the pyridine-like rings of NAD and NADP derived from?

    <p>Vitamin B3</p> Signup and view all the answers

    How can the formation of NADH be monitored using spectrophotometry?

    <p>Measure the change of absorbance at 340 nm</p> Signup and view all the answers

    Which type of ion is accepted by NAD+ and NADP+ during reduction reactions?

    <p>Hydride ion</p> Signup and view all the answers

    Which enzyme uses NADH as a cofactor for the transfer of electrons in cellular reactions?

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

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