Biochemistry: Concepts and Connections (2nd Edition)
2nd Edition
ISBN: 9780134641621
Author: Dean R. Appling, Spencer J. Anthony-Cahill, Christopher K. Mathews
Publisher: PEARSON
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Chapter 14, Problem 2P
When pure reduced cytochrome c is added to carefully prepared mitochondria along with ADP Pi, antimycin A, and oxygen, the cytochrome c becomes oxidized, and ATP is formed, with a P/O ratio approaching 1.0.
- Indicate the probable flow of electrons in this system.
- Why was antimycin A added?
- What does this experiment tell you about the location of coupling sites for oxidative phosphorylation?
- Write a balanced equation for the overall reaction (including cyt c oxidation and ATP synthesis).
- Calculate ΔGO' for the above reaction, using E'o values from Table 14.1 and a ΔGO' value for ATP hydrolysis of -32.2 kJ / mol.
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When pure reduced cytochrome c is added to carefully prepared mito-
chondria along with ADP, P, antimycin A, and oxygen, the cytochrome c
becomes oxidized, and ATP is formed, with a P/O ratio approaching 1. Why
was antimycin A added, and what does this experiment tell you about the
location of coupling sites?
When pure reduced cytochrome c is added to carefully prepared
mitochondria along with ADP, P, antimycin A, and oxygen, the
cytochrome c becomes oxidized, and ATP is formed, with a P/o
ratio approaching 1.0.
(a) Indicate the probable flow of electrons in this system.
(b) Why was antimycin A added?
(c) What does this experiment tell you about the location of cou-
pling sites for oxidative phosphorylation?
(d) Write a balanced equation for the overall reaction (including cyt
c oxidation and ATP synthesis).
The reduction potentials of iron in each of the cytochromes in the electron transport complexesvary from 0.The reduction potentials of iron in each of the cytochromes in the electron transport complexes vary from 0.1 V to 0.39 V. Explain why these different values are necessary for the operation of this process
Chapter 14 Solutions
Biochemistry: Concepts and Connections (2nd Edition)
Ch. 14 - Prob. 1PCh. 14 - When pure reduced cytochrome c is added to...Ch. 14 - Freshly prepared mitochondria were incubated with...Ch. 14 - Prob. 4PCh. 14 - Prob. 5PCh. 14 - Prob. 6PCh. 14 - Intramitochondrial ATP concentrations are about 5...Ch. 14 - Prob. 8PCh. 14 - Prob. 9PCh. 14 - Years ago there was interest in using uncouplers...
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- A new ATP-producing protein is discovered that couples ATP production to the oxidation of NADPH by oxidative phosphorylation. Assume that the value of ΔGo for ATP synthesis is 30 kJ•mol−1. If this protein only produces 1 molecule of ATP per reaction that consumes one NADPH: a. How much free energy is wasted, under standard conditions?b. How many more ATP molecules could be created by a perfectly efficient electron transport chain from one NADPH?arrow_forwardThe cytochromes are heme-containing proteins that function as electron carriers in the mitochondria. Calculate the difference in the reduction potential (AE°') and the change in the standard free energy (AG°) when the electron flow is from the carrier with the lower reduction potential to the higher. cytochrome c₁ (Fe³+) + e¯ = cytochrome c₁ (Fe2+) E°' = 0.22 V cytochrome c (Fe³+) + e¯ = cytochrome c (Fe²+) E°' = 0.254 V Calculate AE°' and AG°'. AE°' = AG°' = V kJ/molarrow_forwardTo carefully prepared mitochondria were added succinate, oxidized cytochrome c, ADP, orthophosphate, and sodium cyanide. The overall balanced equation is: succinate + 2 cyt c(ox) + ADP + Pi --> fumarate + 2 cyt c(red) + ATP + H2O The standard state free energy of this system is O -10.3 kJ/mol 42.5 kJ/mol O 10.3 kJ/mol -42.5 kJ/molarrow_forward
- Compare the delta ΔG0' values for the oxidation of succinate by NAD+ and by FAD. Use the data given in Table 18.1 to find the E0' of the NAD+-NADH and fumarate-succinate couples, and assume that E0' for the FAD – FADH2 redox couple is nearly 0.05 V. Why is FAD rather than NAD+ the electron acceptor in the reaction catalyzed by succinate dehydrogenase?arrow_forwardThe TCA cycle enzyme aconitase and the electron transport proteins have chromophores that absorb in the visible part of the spectrum, and therefore mitochondria have a dark brown color. In contrast, none of the glycolytic enzymes have visible spectrum chromophores. Which of the following statements is true? Question 3 Select one: a. Migrating birds, such as ducks have “white” breast meat, because flying long distances requires anaerobic ATP generation. d. The leg muscle of turkeys is specialized for anaerobic ATP generation via glycolysis. e. The flight muscle of turkeys is specialized for anaerobic ATP generation via glycolysis. f. None of the answers are correct.arrow_forwardCitrate and isocitrate are interconverted via the enzyme aconitase: The standard free energy change for this reaction is +6.7 kJ/mol. In my pet llama's mitochondria, the free energy change was measured to be +0.8 kJ/mol. (No llamas were harmed in this experiment!) a. Calculate the [isocitrate]/[citrate] ratio in these mitochondria. b. If [isocitrate] =0.03 mM, what is [citrate]?arrow_forward
- You are isolating mitochondria from insect cells and incubating in a test tube with 0.005 M FADH2, 0.05 M ADP and 0.05 M Pi. Assuming, these 3 can enter mitochondria at no cost,no glucose/products of glucose metabolism remain in the isolated mitochondria, and oxygen is present. Part 1) If all expected reactions go to completion, how much ATP is expected formed? (0 M)(0.02 M) (0.03 M) (0.05 M) (0.1 M) (0.005 M) (0.01 M) (0.015 M) Part 2) The ratio of FADH2/FAD at completion of all expected reactions would be? (2) (>>2) (0) (1) Part 3) After completion of all expected reactions, ratio of H ion concentration inside vs. outside the mitochondrial inner membrane should be? (<1) (~1) (>1)(0) Please provide brief explanationarrow_forwardTwo biochemistry students are about to usemitochondria isolated from rat liver for an experiment on oxidative phosphorylation. The directions for the experiment specifyaddition of purified cytochrome c from any source to the reactionmixture. Why is the added cytochrome c needed? Why does thesource not have to be the same as that of the mitochondria?arrow_forwardExplain why the coupled reaction ATP → ADP + Pi in the P-class ion pump mechanism does not involve direct hydrolysis of the phosphoanhydride bond.arrow_forward
- ATP Synthase is known to catalyze the synthesis of ATP with a ΔG°’ close to zero, and a Keq' close to. Why is the value of ΔG°’ different from the known value which is 30.5 kJ/mol (the energy for the reverse of ATP hydrolysis)? If the Keq' value is close to one, how is it ensured that the reaction is driven to the product side and more ATP is obtained?arrow_forwardShown below are reduction potentials for four half-reactions. Which of the coupled reactions is favorable? (Note that for Cytochrome c you must multiply the reduction potential by 2 for each coupled reaction because only one electron is involved) a) 2 Cytochrome c (Fe3+) + H2O ó 2 Cytochrome c (Fe2+) + O2 b) NADH + Succinate- ó NAD+ + Fumarate- c) Fumarate- + H2O ó Succinate- + O2 d) All of the abovearrow_forward(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 torrarrow_forward
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