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Chapter 14: Problem 12

If cyanide is added to tightly coupled mitochondria that are actively oxidizing succinate, A. subsequent addition of 2,4 -dinitrophenol will cause ATP hydrolysis. B. subsequent addition of 2,4 -dinitrophenol will restore succinate oxidation. C. electron flow will cease, but ATP synthesis will continue. D. electron flow will cease, but ATP synthesis can be restored by subsequent addition of 2,4 -dinitrophenol. E. subsequent addition of 2,4 -dinitrophenol and the phosphorylation inhibitor, oligomycin, will cause ATP hydrolysis.

Short Answer

Expert verified
Answer: Subsequent addition of 2,4-dinitrophenol will restore succinate oxidation.

Step by step solution

01

Understand the role of Cyanide

Cyanide is a potent inhibitor of mitochondrial electron transport chain (ETC). It binds to the ferric iron (Fe3+) of Cytochrome c oxidase (Complex IV), hindering electron transfer and stopping oxidative phosphorylation, which hampers ATP synthesis. In this case, cyanide has been added to the mitochondria oxidizing succinate, so it inhibits the ETC, stopping electron flow and ATP synthesis. Step 2: Know the function of 2,4-dinitrophenol
02

Understand the function of 2,4-dinitrophenol

2,4-dinitrophenol (DNP) is an uncoupler of oxidative phosphorylation in mitochondria. It acts by carrying protons across the inner mitochondrial membrane, dissipating the proton gradient that drives ATP synthesis. DNP does not directly affect the electron transport chain, so it allows electron flow to continue. Step 3: Analyze the given options
03

Analyze the given options

Now that we understand the roles of cyanide and DNP, we can analyze each option: A. ATP hydrolysis will not occur because DNP does not directly affect ATPase activity. B. This option is true because adding DNP will uncouple oxidative phosphorylation allowing succinate oxidation to continue, restoring electron flow. C. Electron flow ceases due to cyanide's action, but ATP synthesis will not continue, so this is incorrect. D. Electron flow ceases because of cyanide's action. Adding DNP will only uncouple oxidative phosphorylation, but it will not restore the electron flow inhibited by cyanide, so this is incorrect. E. ATP hydrolysis does not occur because DNP does not directly affect ATPase activity. Oligomycin, a phosphorylation inhibitor, will instead inhibit ATP synthesis. The correct answer is option B: subsequent addition of 2,4-dinitrophenol will restore succinate oxidation.

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Most popular questions from this chapter

During the transfer of electrons to \(\mathrm{O}_{2}\) via the mitochondrial electron transport chain, A. the energy released is used to translocate protons across the inner membrane. B. a proton gradient is generated with the matrix now being more positive than the intermembrane space. C. pumping of protons across the membrane occurs each time electrons are moved. D. no charge gradient develops because an OH" moves each time a proton does. E. the energy is used directly in the addition of \(P_{i}\) to ADP to form ATP.

Suppose the specific defect were a mutant pyruvate dehydrogenase (the first catalytic subunit) with poor binding of its prosthetic group. In this type of defect, sometimes greatly increasing the dietary precursor of the prosthetic group is helpful. In this case, increasing which of the following might be helpful? A. Lipoic acid B. Niacin (for NAD) C. Pantothenic acid (for CoA) D. Riboflavin (for FAD) E. Thiamin (for TPP)

All of the following starements are correct except A. reactive oxygen species (oxygen radicals) result when there is a concerted addition of four electrons at a time to \(\mathrm{O}_{2}\) B. superoxide anion \(\left(\mathrm{O}_{2}^{-}\right)\) and hydroxyl radical (.OH) are two forms of reactive oxygen. C. superoxide dismutase is a naturally occurring enzyme that protects against damage by converting \(\mathrm{O}_{2}^{-}\) to \(\mathrm{H}_{2} \mathrm{O}_{2}\) D. reactive oxygen species damage phospholipids, proteins, and nucleic acids. E. glutathione protects against \(\mathrm{H}_{2} \mathrm{O}_{2}\) by reducing it to water.

For the reaction \(A \rightleftharpoons B, \Delta G^{0}=-29.7 \mathrm{kJ} / \mathrm{mol} .\) At \(37^{\circ} \mathrm{C},-2.303\) \(R T=-5.94 \mathrm{kJ} / \mathrm{mol} .\) What is the equilibrium ratio of B/A?

ATP synthase (also known as complex \(V\) ) consists of two domains, \(F_{1}\) and \(F_{0}\) A. \(\mathrm{F}_{1}\) and \(\mathrm{F}_{\mathrm{o}}\) are both integral membrane protein complexes of the outer membrane. B. \(F_{1}\) domain provides a channel for translocation of protons across the membrane. C. \(F_{1}\) binds ATP but not ADP. D. \(F_{1}\) domain catalyzes the synthesis of ATP. E. Only the \(F_{0}\) domain contains more than one subunit.
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