27 Questions
Which group is transferred when the oxygen of the nucleophile attacks the β position of ATP?
Pyrophosphoryl
What is the cellular ATP concentration like in most cells?
Usually far above equilibrium concentration
Why does the hydrolysis of PhosphoEnolPyruvate (PEP) catalyzed by pyruvate kinase have a large standard free energy of hydrolysis?
Resonance stabilization and favorable solvation of the products
What happens when the oxygen of the nucleophile attacks the α position of ATP?
More than one of the choices is correct
What kind of group is transferred when attacking the γ position of ATP with oxygen of the nucleophile?
Phosphoryl
All the factors below contribute to the large standard free energy of hydrolysis in PEP catalyzed by pyruvate kinase EXCEPT
Resonance stabilization within the reactant molecule
What is the most highly oxidized form of carbon found in living systems?
Carbon dioxide
In biochemical oxidation-reduction reactions, how many electrons are typically involved in transfer?
Two electrons
What accompanies electron transfer in order to keep charges in balance?
Proton transfer
In dehydrogenases, like lactate dehydrogenase, how does the reaction typically proceed?
Through a stepwise transfer of proton and hydride
Which enzyme catalyzes the reaction of lactate to pyruvate in cells?
Lactate dehydrogenase
Which flavin cofactor allows single or double electron transfers?
Both FAD and FMN
What forms when FAD or FMN accepts only one hydrogen atom?
Semiquinone
What vitamin is the isoalloxazine ring of FAD and FMN derived from?
Vitamin B2
What deficiency leads to Stomatitis?
Vitamin B2 deficiency
Why does the hydrolysis of 1,3-bisphosphoglycerate (1,3-BPG) have a large standard free energy of hydrolysis?
The removal of 3-phosphoglyceric acid by further metabolism and formation of the ion favor the forward reaction.
Which of the following statements about the hydrolysis of phosphocreatine (PCr) is correct?
The release of inorganic phosphate (Pi) and the resonance stabilization of creatine favor the forward reaction.
What is the overall result of the flow of phosphoryl groups catalyzed by kinases?
It results in an overall loss of free energy under intracellular conditions.
What is the significance of the hydrolysis of low-energy phosphate compounds?
It releases inorganic phosphate (Pi), which has a lower phosphoryl group transfer potential.
What is the primary factor that influences the actual free-energy change (ΔG) of ATP hydrolysis, in addition to the standard free energy (ΔG°')?
Concentrations of reactants and products
In the two-step reaction catalyzed by ATP-dependent glutamine synthetase, what is the first step?
A phosphoryl group is transferred from ATP to glutamate
In the context of ATP hydrolysis, what is the role of the enzyme that catalyzes the reaction?
To decrease the activation energy barrier of the reaction
What are the common redox cofactors that allow two-electron transfer in biological systems?
NAD and NADP
What vitamin is the pyridine-like rings of NAD and NADP derived from?
Vitamin B3
How can the formation of NADH be monitored using spectrophotometry?
Measure the change of absorbance at 340 nm
Which type of ion is accepted by NAD+ and NADP+ during reduction reactions?
Hydride ion
Which enzyme uses NADH as a cofactor for the transfer of electrons in cellular reactions?
Lactate Dehydrogenase
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