1. Cyanide, oligomycin, and 2,4-dinitrophenol are all inhibitors of oxidative phosphorylation in mitochon-dria. Provide an explanation to the following conditions regarding these potent inhibitors.(a)Explain why adding cyanide to an active in vitro suspension of mitochondria blocks ATPsynthesis. What happens to the rate of ATP synthesis when 2,4-dinitrophenol is added to this mitochon-drial suspension after it was treated with cyanide?(b)Explain why the rate of oxygen consumption decreases in an in vitro suspension of mito-chondria when oligomycin is added. What happens to the rate of oxygen consumption in this oligomycin-inhibited system after adding 2,4-dinitrophenol? Explain.

ETC consists of four protein complexes called Complex I, II, III and IV that transport electrons…

Answered: 1. Cyanide, oligomycin, and…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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(a) Consider the oxidation of malate to oxaloacetate by NAD*: malate + NAD+ → oxaloacetate + NADH + H+ In yeast mitochondria, where the pH = 8.1, this reaction is exergonic only at low oxaloacetate concentrations. Assuming a pH = 8.1, a temperature of 37 °C, and the steady-state concentrations given below, calculate the maximum concentration of oxaloacetate at which the reaction will still be exergonic. malate + NAD*→ oxaloacetate + NADH + H* lactate + NAD →→ pyruvate + NADH + H+ half reaction Pyruvate + 2H+ + 2e → lactate Pyruvate + CO₂ + H + 2e → malate Intracellular steady state concentrations: malate = 410 μM; NAD = 20.0 mM; pyruvate = 3.22 mM; NADH = 290 μM; AG=+29.7 kJ/mol AG¹ = +25.1 kJ/mol E° (V) - 0.190 - 0.330 lactate 1.1 mM CO₂ = 15.5 torr
The glutamate dehydrogenase (GDH) catalyses the following reaction: +H₂N- H - - CH₂ - CH₂ COO acide glutamique COO™® + NAD+ + H₂O GDH COO C: CH₂ CH₂ COO™ O + NH4+ NADH + H* The activity of GDH is monitored in the sense of the formation of glutamate using the following conditions: -0.2 mL of 5 M ammonium sulphate 2.4 mL of buffer at pH 8 0.1 mL of NADH at 6.15 mg.mL-¹ (M = 709 g.mol-¹) 0.2 mL of 1 M a-ketoglutarate solution Warm mixture at 25 °C for 5 min - Add 0.1 mL of GDH solution containing 1.6 mg.mL-¹protein to start the reaction. acide a-cétoglutarique The change in absorbance at 340 nm is monitored, in a 1-cm cuvette, every minute for 10 min. Results are given in the table below: Data: ENADH at 340 nm = 6220 M¹.cm¹ Time (min) 1 2 3 4 5 6 7 8 9 1.760 1.718 1.675 1.635 1.595 1.550 1.510 1.489 1.476 A340 10 1.451 - Draw the graph A = f(t). Calculate A340 at t = 0 and place this point on the curve. - Comment the shape of the curve, particularly the portion that corresponds to a…
The phosphorylation and oxidative decarboxylation of oxaloacetate by inorganic phosphate (Pi) to make phosphoenolpyruvate and carbon dioxide is endergonic under intracellular conditions. It is characterized by this equation: Oxaloacetate + Pi ←→ Phosphoenolpyruvate + H2O + CO2 ΔG’ = +24.6 kJ/mol The synthesis of GTP from GDP and inorganic phosphate (Pi) in solution is endergonic under intracellular conditions, and it is characterized by this equation: GDP + Pi ←→ GTP + H2O ΔG’ = +30.5 kJ/mol Write a new net thermodynamically coupled reaction equation that describes the synthesis of phosphoenolpyruvate from oxaloacetate using the hydrolysis of GTP to power the reaction and calculate the new net ΔG’ of this reaction. Show all of your work.
The formation of glutamine from glutamate and ammonium ions requires 14.2 kJ mol-1 of energy input. It is driven by the hydrolysis of ATP to ADP mediated by the enzyme glutamine synthetase. {a) Given that the change in Gibbs energy for the hydrolysis of ATP corresponds to ΔG = -31 kJ mol-1, under the conditions prevailing in a typical cell , can the hydrolysis drive the formation of glutamine? (b) What amount {in moles) of ATP must be hydrolysed to form 1 mol glutamine? (c) Suppose that the radius of a typical cell is 10 μm and that inside it 106 ATP molecules are hydrolysed each second. What is the power density of the cell in watts per cubic metre (1W = 1 Js- 1)? (d) A computer battery delivers about 15 Wand has a volume of 100 cm3 Which has the greater power density, the biological cell or the battery?
In the hydrolysis of ATP to ADP and Pi, the equilibrium concentration of ATP is too small to be measured accurately. A better way of determining K’eq, and hence ΔG◦’ of this reaction, is to break it up into two steps whose values of ΔG◦’ can be accurately determined. This has been done using the following pair of reactions (the first being catalyzed by glutamine synthetase): (1) ATP + glutamate + NH3 ⇌ ADP + Pi + glutamine + H+ ΔG1◦’= -16.3 kJ/mol (2) glutamate + NH3 ⇌ glutamine + H2O + H+ ΔG2◦’= 14.2 kJ/mol What is the ΔG◦’ of ATP hydrolysis according to these data and is the overall reaction spontaneous? What is the value of the equilibrium constant for the overall reaction at 25.0 °C. If the concentration of ATP at equilibrium is 20.0 mM and the concentration of ADP at equilibrium is 50 nM. What is the concentration the phosphate group (in mM) at equilibrium?
Aconitase catalyzes the reaction: citrate ↔ HisocitrateThe standard free energy change, ΔG°′, for this reaction is +6.3 kJ/mol.However, the observed free energy change (ΔG) for this reaction in mammalian mitochondria at 25°C is ∼0 kJ>mol (Table 13.2).(a) Calculate the ratio of [isocitrate]>[citrate] in mitochondria.(b) Is this reaction likely to be a control point for the citric acid cycle? Whyor why not?
About the process of industrial production of ethanol by the yeast Saccharomyces cerevisiae, mark the correct alternatives: (a) the cells must be cultured in anaerobic conditions to activate the metabolic pathway of ethanol production (b). the presence of oxygen is required to allow regeneration of the NAD+ cofactor (c). good oxygenation of the medium is important to favor the formation of greater amounts of ATP (d).the production of ethanol is always accompanied by the formation of glycerol (e). the sugar present in the culture medium is completely oxidized to CO2 and water
In another key reaction in glycolysis, dihydroxyacetone phosphate (DHAP)is isomerized into glyceraldehyde-3-phosphate (GAP): Because ΔG°′ is positive, the equilibrium lies to the left.(a) Calculate the equilibrium constant and the equilibrium fraction of GAPfrom the above, at 37 °C.(b) In the cell, depletion of GAP makes the reaction proceed. What will ΔGbe if the concentration of GAP is always kept at 1/100 of the concentrationof DHAP?
The glucose/glucose-6-phosphate substrate cycle involves distinct reactions of glycolysis and gluconcogenesis that interconvert these two metabolites. Assume that under physiological conditions, [ATP] = [ADP] and [Pi] =1 mM. Consider the following glycolytic reaction catalyzed by hexokinase: ATP + glucose = AG' = -16.7 kJ/mol ADP + glucose-6-phosphate (a) Calculate the equilibrium constant (K) for this reaction at 298 K, and from that, calculate the maximum [glucose-6-phosphate]/[glucose] ratio that would exist under conditions where the reaction is still thermody- namically favorable. (b) The reverse of this interconversion in gluconeogenesis is catalyzed by glucose-6-phosphatase: glucose-6-phosphate + H,0 = glucose + P, AGr = -13.8 kJ/mol K= 262 for this reaction. Calculate the maximum ratio of [glucose]/ [glucose-6-phosphate] that would exist under conditions where the reaction is still thermodynamically favorable. (c) Under what cellular conditions would both directions in the…
The glucose/glucose-6-phosphate substrate cycle involves distinct reactions of glycolysis and gluconeogenesis that interconvert these two metabolites. Assume that under physiological conditions, [ATP] = [ADP]; [P;] = 1 mM. Consider the glycolytic reaction catalyzed by hexokinase: ATP + glucose ADP + glucose-6-phosphate AG = - 16.7 kJ/mol (a) Calculate the equilibrium constant (K) for this reaction at 298°K, and from that, calculate the maximum [glucose-6-phosphate]/ Iglucose] ratio that would exist under conditions where the reaction is still thermodynamically favorable. (b) Reversal of this interconversion in gluconeogenesis is catalyzed by glucose-6-phosphatase: glucose-6-phosphate + H20 = glucose + P AG" = -13.8 kJ/mol
During glycogen synthesis, glucose-1P is converted into a molecule called UDPG. This reaction also cleaves uridine triphosphate (UTP) forming uridine monophosphate and pyrophosphate (PPi). Provide four reasons why UTP can be used to power this reaction (no diagrams necessary).
15.13) The NADH that is produced by glycolysis is not able to pass through the inner mitochondrial membrane to enter the matrix region and undergo oxidative phosphorylation. Name the two processes in which the energy from NADH made in glycolysis can enter the mitochondrial matrix. ANSWER: 1) malate-aspartate shuttle 2) glycerol 3-phosphate shuttle EXPLANATION: Oxidative phosphorylation requires that NADH be located within the mitochondrial matrix. Since pyruvate oxidation/decarboxylation and the reactions of the citric acid cycle occur in the mitochondrial matrix, the NADH created in those processes can immediately undergo oxidative phosphorylation. The NADH that is produced by glycolysis is able to pass through the outer mitochondrial membrane and enter the intermembrane space; however, it is not able to pass through the inner mitochondrial membrane to enter the matrix region. In order for the energy from this NADH to be utilized, it must be processed through "NADH shuttles." The two…

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