Choose any/all that apply to the proton-motive force and ATP synthesis.The active pumping of protons through ATP synthase against their concentration gradientprovides the energy needed for ATP synthesis.Rotation of the y subunit creates conformational changes in the active sites of ATP synthasethat drive the release of ATP from the enzyme.Each 3 subunit of ATP synthase has a distinct amino acid sequence that accounts for thethree different active sites present in the enzyme.The ATP molecules produced from the pair of electrons provided by NADH have greaterpotential energy than the ATP molecules produced from the pair of electrons provided byFADH₂.Inhibition of either ATP synthase or ATP translocase will stop flux through the electron-transport chain.

The active pumping of protons through ATP synthase against their concentration gradient provides the…

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Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter21: Photosynthesis

Section: Chapter Questions

Problem 15P

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Figure 27.3 illustrates the response of R (ATP-regenerating) and U (ATP-utilizing) enzymes to energy charge. a. Would hexokinase be an R enzyme or a U enzyme? Would glutamine: PRPP amidotransferase, the second enzyme in purine biosynthesis, be an R enzyme or a U enzyme? b. If energy charge = 0.5: Is the activity of hexokinase high or low? Is ribose-5-P pyrophosphokinase activity high or low? c. If energy charge = 0.95: Is the activity of hexokinase high or low? Is ribose-5-P pyrophosphokinase activity high or low?
Choose any/all that apply to the proton-motive force and ATP synthesis. The active pumping of protons through ATP synthase against their concentration gradient provides the energy needed for ATP synthesis. The ATP molecules produced from the pair of electrons provided by NADH have greater potential energy than the ATP molecules produced from the pair of electrons provided by FADH2. Each Beta subunit of ATP synthase has a distinct amino acid sequence that accounts for the three different active sites present in the enzyme. Rotation of the Y subunit creates conformational changes in the active sites of ATP synthase that drive the release of ATP from the enzyme. Inhibition of either ATP synthase or ATP translocase will stop flux through the electron-transport chain.
V-class proton pumps run backward relative to the F-class ATP synthase. Consider the cartoon, which shows the conformations of the beta-subunits and ATPIADP + Pj of the F-class synthase. Which of the following associations between the conformation of the beta subunit and ATP/ADP + P¡ is correct for V- Binding Change Mechanism loose binding ADP+P ATP ATP class pumps? C repeat ADP + P, ADP АТР tight binding АТР +P оpen АТР O The open conformation releases ATP. Hydrolysis of ATP to ADP + P¡ drives the change from tight to loose. O Binding of ADP + P¡ drives change from open to loose. Hydrolysis of ATP to ADP + Pj drives the change from open to loose.
Enzymes normally enhance the rates of biochemical reactions by preferentially binding and stabilizing the transition states rather than either the substrates or the products of a reaction. The F|-subunit of ATP synthase does not fit this norm so well as tight binding to ATP rather than a transition state is employed to make ATP. Explain the binding-change model of the mechanism of ATP-synthase. How and why is the proton-motive force used in the reaction cycle of ATP synthase?
The standard free energy change for ATP hydrolysis is -7.3kcal/mol. The free energy change under typical cellular conditions is about -12kcal/mol. Why is there a difference? O The hydrolysis of ATP must be more difficult in the cellular environment O There is more ATP and less ADP in the cell O The cellular environment is anaerobic so O2 levels are reduced O The enzymes involved in the reaction are trapped in organelles
In the rete mirabile serving the red swimming muscles oftunas, some key enzymes of catabolism show gradients ofconcentration: They are more concentrated at the cold end of therete, and less concentrated at the warm end. These variationsparallel variations that are often seen in the thermal acclimationof poikilotherms, when enzyme concentrations rise duringacclimation to cold and fall during acclimation to heat. Whatdo you think could be some of the reasons for these spatial andtemporal variations in enzyme concentration? Why not havethe highest observed enzyme concentrations everywhere at alltimes?
Whatis the main idea behind the conformational coupling mechanism for ATP synthase? Describe the three conformational states.
Is increasing the P; concentration a reasonable way to couple ATP hydrolysis and glucose phosphorylation? Yes. Increasing the concentration of P; would decrease K'eq and shift equilibrium to the right. No. The phosphate salts of divalent cations would be present in excess and precipitate out. No. The extra P; would give a negative AG", but would give a positive AG. Yes. The extra ATP hydrolysis would provide enough free energy to drive the phosphorylation reaction.
The phosphorylation of glucose to glucose 6-phosphate is the initial step in the catabolism of glucose. The direct phosphorylation of glucose by P, is described by the equation Glucose + P→ glucose 6-phosphate + H₂O AG 13.8 kJ/mol = Coupling ATP hydrolysis to glucose phosphorylation makes thermodynamic sense, but consider how the coupling might take place. Given that coupling requires a common intermediate, one conceivable mechanism is to use ATP hydrolysis to raise the intracellular concentration of P₁. The increase in P; concentration would drive the unfavorable phosphorylation of glucose by P₁.
The following diagram shows reaction curves for aspartate transcarbamoylase (ATCase) with carbamoylphosphate and different concentrations of aspartate, in the absence of ATP (curve 1) and presence of ATP (curve 2). What do the shapes of the curves tell us about the ATCase enzyme? 2 جر [aspartate] It binds substrate through a sequential mechanism. It binds substte cooperatively. It obeys Michaelis-Menten kinetics. It binds substrate through a concerted mechanism.
Allosteric regulation of an enzyme is accomplished when the enzyme pathway's product accumulates and then binds to the active (catalytic) site of the enzyme O True False
Calculate the ATP yield for the full catabolism of a phospholipid containing ethanolamine, C18:3 Δ9, 12, 15 and oleic acid. Include any ATP “expenses” or “income”. This will be a complex problem—neatly show your work and justify your choices.

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