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ATP and CTP regulate aspartate transcarbamoylase (ATCase)
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Regulation of enzyme activity
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BC 351

Exam 4

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ATP and CTP regulate aspartate transcarbamoylase (ATCase) by binding the R subunit and stabilizing ATCase in the R and T states, respectively.
Regulation of enzyme activity can affect the KM or VMAX or both of the enzyme
The biosynthetic pathway for the two amino acids, E and H, is shown in the figure above. Enzyme T is most likely to be subject to feedback inhibition by C alone (See image in Cram.com)
In resting muscle cells the regulatory molecule that would accumulate and the enzyme that would be more active are ATP and glycogen synthase
Mutations affecting the KD for PALA are not found because A, B and C, but not D.
The enzyme pictured above has activity in the cell that varies continuously from very high to very low because it is the activity of the population of enzyme molecules that determines the cellular activity.
You are studying an enzyme that has a 3-fold increase in KM, but no change in VMax upon phosphorylation. The best interpretation of your result is your enzyme is positively regulated by a protein phosphatase
Regulation of enzyme activity often is found to integrate several types of signals
For ATP hydrolysis, ATP ADP + Pi, what is the effect of changing the reaction conditions from standard chemical conditions to biochemical standard conditions (other than the ATP and ADP concentrations) on ΔG of the reaction? The ΔG of the reaction will be more negative at a given ADP/ATP ratio
Regulation of metabolic pathways occurs through modulating the activity of paired enzymes catalyzing 􀀂bypass􀀃 reactions in the catabolic and anabolic pathways.
In this branched metabolic pathway, a red arrow with a minus sign symbolizes inhibition of a metabolic step by an end product. The reaction that would continue if both Q and S were present in the cell in high concentrations? L ----> N
The NADH produced via the citric acid cycle is fed into oxidative phosphorylation
The result of the citric acid cycle and oxidative phosphorylation is oxidation of nutrients to produce usable chemical energy in the form of ATP
The final electron acceptor in the electron transport chain is oxygen
How many electrons are removed from QH2 in Complex III of the electron transport chain? 2
How many ATP are produced from glycolysis alone? 2
4 electrons in complex 4 are transferred from 4 molecules of cytochrome c and transferred to O2
How many protons are translocated in complex III? 4
In complex I 2 electrons from NADH are transferred to ubiquinone (Q)
The enzyme in complex IV is cytochrome c oxidase
Which of the following statements about allosteric control of enzymatic activity is false? Heterotropic allosteric effectors compete with substrate for binding sites.
Which of the following electron carriers is not able to transfer one electron at a time? NADH
Almost all of the oxygen (O2) one consumes in breathing is converted to: water.
Which of the following is not a feature of complex IV? In order to generate two water molecules, complex IV must go through the catalytic cycle two times.
Under aerobic conditions most of the ATP produced is through oxidative phosphorylation.
A reaction at equilibrium in a metabolic pathway is a rapid and reversible step.
Allosteric enzymes usually have more than one polypeptide chain.
All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are also involved in the reversal of this flow (gluconeogenesis) except: phosphofructokinase-1
Which one of the following statements about gluconeogenesis is false? It consists entirely of the reactions of glycolysis, operating in the reverse direction.
The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except oxidation of NADH to NAD+.
The regulated steps in glycolysis and gluconeogenesis are paired, but involve different enzymes.
ATP synthase is often described as a molecular motor
Which of the following is not true of the citric acid cycle? All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane.
Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex? Biotin participates in the decarboxylation.
Conversion of 1 mol of acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of: 1 mol of FADH2.
In the reoxidation of QH2 by purified ubiquinone-cytochrome c reductase (Complex III) from heart muscle, the overall stoichiometry of the reaction requires 2 mol of cytochrome c per mole of QH2 because: cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor.
When a glucose molecule is broken down to CO2 in glycolysis and the TCA cycle, little ATP is directly produced, most of the energy is stored as NADH.
Antimycin A blocks electron transfer between cytochromes b and c1. If intact mitochondria were incubated with antimycin A, excess NADH, and an adequate supply of O2, which of the following would be found in the oxidized state? Cytochrome a3
What happens to the NADH produced in the TCA cycle? It is oxidized to produce ATP.
The free energy stored in the electrochemical gradient produced by the electron transport chain is referred to as proton motive force, pmf, or ΔP.
Reduced QH2 is not formed by which of the following? Complex III and cytochrome c
Which of the following statements about the chemiosmotic theory is false? The membrane ATPase, which plays an important role in other hypotheses for energy coupling, has no significant role in the chemiosmotic theory.
Which of the following statements about energy conservation in the mitochondrion is false? Uncouplers (such as dinitrophenol) have exactly the same effect on electron transfer as inhibitors such as cyanide; both block further electron transfer to oxygen.
2,4-Dinitrophenol and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4-Dinitrophenol is an uncoupling agent; oligomycin blocks the ATP synthesis reaction itself. Therefore, 2,4-dinitrophenol will: allow electron transfer in the presence of oligomycin.
Which of the following statements about oxidative phosphorylation is FALSE? Protons are moved across the outer mitochondrial membrane in order to produce potential energy
The proton motive force is used by ATP synthase to produce ATP from ADP
During oxidative phosphorylation, the proton motive force that is generated by electron transport is used to: induce a conformational change in the ATP synthase.
In normal mitochondria, the rate of NADH consumption (oxidation) will: be increased in active muscle, decreased in inactive muscle, be very low if the ATP synthase is inhibited, increase when an uncoupler is added decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3 complex. decrease if m
The mitochondrial ATP synthase uses the energy stored in the proton gradient to drive conformational changes in the F1 component beta subunit (ATP synthase).
When the ∆G'° of the ATP synthesis reaction is measured on the surface of the ATP synthase enzyme, it is found to be close to zero. This is thought to be due to: stabilization of ATP relative to ADP by enzyme binding.
Cyanide, oligomycin, and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic phosphorylation. Which of the following statements correctly describes the mode of action of the three inhibitors? Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit the synthesis of ATP.
Which of the following statements about the chemiosmotic theory is correct? Electron transfer in mitochondria is accompanied by an asymmetric release of protons on one side of the inner mitochondrial membrane.
A mechanism not used by cells to regulate enzyme activities is substrate diffusion rate control.
The observations are best explained by: In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.
It is true that the ΔG° for the oxidation of the aldehyde group on glyceraldehyde 3-phosphate to form a carboxylic acid is more negative than the ΔG° for ATP hydrolysis.
If the glyceraldehyde 3-P dehydrogenase active site cysteine (-SH) were replaced with a serine (-OH), the effect would be oxidization of the substrate without releasing it.
Arsenate is preferred over phosphate by murderers, but not cells allows 3-P glycerate formation in the absence of ATP synthesis in glycolysis.
Radiolabeled fluoro-2-deoxyglucose labels tumor cells brightly in positron emission tomography (PET). This bright labeling is due to cancer cells using high levels of glucose and producing large amounts of lactate.
The growth of nonphotosynthetic bacteria, but not animal cells, can occur on the carbon source fatty acids
Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true? High levels of ATP act as an allosteric activator of anabolic pathways
Regulation of glycolysis vs. gluconeogenesis is through the response of the key enzymes to indicators of energy charge in the cell like ATP and AMP
The plot of the effect of ATP and AMP on PFK-1 activity above indicates ATP is a substrate and inhibitor
The plot of the effect of F2,6bisP on PFK-1 activity above indicates F2,6bisP is a heteroallosteric activator.
Regulation of glycolysis and gluconeogenesis in the liver functions to stabilize the glucose levels in the blood through glucagon activation of PKA activity.
When the glucagon concentration in the blood increases the enzymatic activity decreases for PhosphoFructoKinase-2.
A deficiency in the vitamin thiamine results in higher than normal levels of pyruvate and α-ketoglutarate in the blood suggesting that thiamine is necessary for the function of specific dehydrogenases
If citrate (C6H8O7) were completely oxidized to CO2 and H2O, the number of molecules of O2 consumed per molecule of citrate would be around 5
The reaction of the citric acid cycle that is most similar to the pyruvate dehydrogenase complex-catalyzed conversion of pyruvate to acetyl-CoA is the conversion of α-ketoglutarate to succinyl-CoA.
The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is them conversion of succinyl-CoA to succinate.
For the following reaction, ΔG'° = +29.7 kJ/mol. L-Malate + NAD+ -->oxaloacetate + NADH + H+ The reaction as written: may occur in cells at certain concentrations of substrate and product
Anaplerotic reactions . produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates
Citrate synthase and the NAD+- specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle. These enzymes are inhibited by ATP and/or NADH.
It is most likely to be true that aerobic respiration arose as an adaptation to increasing levels of oxygen in the atmosphere that had been produced by photosynthesis
It is true that the standard difference in redox potential, ΔE􀀁0, of a redox pair does not depend on the concentration of each member of the pair.
It is true that mitochondrial electron carriers with the highest redox potential generally contain copper ions and/or heme groups.
Addition of reduced ubiquinone to mitochondria lacking cytochrome c would not produce a proton gradient because ubiquinone cannot bind to cytochrome c oxidase (C IV) as required to pass electrons to it
It is true that the pH in the mitochondrial matrix is higher than pH in the intermembrane space.
The direct generation of a proton gradient by electron-transport proteins requires that the oxidized and reduced states of the electron-transport protein have different conformations.
The coupled redox reaction with enough ΔG to synthesize one molecule of ATP from ADP and Pi under standard conditions is the oxidation of cytochrome c by oxygen.
Cotransport of protons from the intermembrane space to the matrix is required for import of acetic acid ions into the matrix from the intermembrane space.
The antibiotic bongkrekic acid inhibits the ATP/ADP transport protein across the inner mitochondrial membrane. To allow electron transport to occur in permeabilize the inner membrane to protons.
The coupling of electron transport to ATP synthesis is likely to be affected in all of these systems by dinitrophenol (carries protons across membranes).
ATP will be synthesized if you add ADP and Pi and shine light on the vesicles.
Each complete rotation of the actin filament requires hydrolysis of three ATP
Created by: potato80
 

 



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