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oxidative phosphorylation

oxidative phosphorylation

Biochemistry
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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In oxidative phosphorylation (mark all that are true)...

Choice 1 of 7:Succinate contributes 2e- to Complex II and 2H+ to the mitochondrial proton gradient.
Choice 2 of 7:NADH in the matrix passes 2 e- to coenzyme Q via Complex I.
Choice 3 of 7:Complexes I, II, III, and IV each contribute to the matrix proton gradient.
Choice 4 of 7:O2 stabilizes the catalytically active conformation of Complex V.
Choice 5 of 7:Reversible protonation of c subunits leads to rotation of the Complex V gamma subunit.
Choice 6 of 7:Each β subunit can bind ATP tightly under the right conditions.
Choice 7 of 7:For every 3 protons that pass across the inner mitochondrial membrane, 1 ATP is produced.
 
Below are screenshots of the answer from two different sources (for your consideration)
In the process of oxidative phosphorylation, succinate is converted to fumarate and this conversion transfers two electrons to Complex ll which is succinate ubiquinone reductase. This subsequently transfers electrons to CoQ, thus coenzyme Q translocates 2 protons to proton gradient. So complex ll doesn't transfer proton to proton gradient. So 1 is incorrect. NADH from alpha keto glutarate in TCA cycle is oxidised to transfer 2electrons to coenzyme Q through complex 1. This translocates 4 protons to proton gradient. So 2 is correct. The complexes that contribute to proton gradient are l, lll and IV. Complex ll doesn't involve in providing proton gradient, but only translocates electrons to coenzyme Q. So option 3 is incorrect. Oxygen acts as final electron acceptor and takes protons to form water molecule. Without oxygen, complex V, ATP synthase doesn't function to prepare ATP by chemiosmosis. Hence oxygen is important for catalytically active Complex V to form ATP, as ATP synthase gets destabilized if protons are not picked up by oxygen. So option 4 is correct. Option 5 is incorrect because reversible rotation of ganna subunit is not through protonation but occurs when proton gradient is collapsed to release ATP when beta subunit changes confirmation to release ATP. Option 6 is incorrect because different beta subunits are at different conformations like loose, tight confirmation to bind to ATP or ADP and Pi. Option 7 is correct because, for every three protons one ATP is produced. So 2,4 and 7 are correct
Transcribed Image Text:In the process of oxidative phosphorylation, succinate is converted to fumarate and this conversion transfers two electrons to Complex ll which is succinate ubiquinone reductase. This subsequently transfers electrons to CoQ, thus coenzyme Q translocates 2 protons to proton gradient. So complex ll doesn't transfer proton to proton gradient. So 1 is incorrect. NADH from alpha keto glutarate in TCA cycle is oxidised to transfer 2electrons to coenzyme Q through complex 1. This translocates 4 protons to proton gradient. So 2 is correct. The complexes that contribute to proton gradient are l, lll and IV. Complex ll doesn't involve in providing proton gradient, but only translocates electrons to coenzyme Q. So option 3 is incorrect. Oxygen acts as final electron acceptor and takes protons to form water molecule. Without oxygen, complex V, ATP synthase doesn't function to prepare ATP by chemiosmosis. Hence oxygen is important for catalytically active Complex V to form ATP, as ATP synthase gets destabilized if protons are not picked up by oxygen. So option 4 is correct. Option 5 is incorrect because reversible rotation of ganna subunit is not through protonation but occurs when proton gradient is collapsed to release ATP when beta subunit changes confirmation to release ATP. Option 6 is incorrect because different beta subunits are at different conformations like loose, tight confirmation to bind to ATP or ADP and Pi. Option 7 is correct because, for every three protons one ATP is produced. So 2,4 and 7 are correct
Answer: Oxidative phosphorylation - It is a metabolic pathway and the electron donars transfer the electrons to the electron acceptors. The process takes place as redox reaction and the energy released is used for the generation of ATP. Choice 1 of 7: TRUE-Succinate contributes 2e- to Complex Il and 2H+ to the mitochondrial proton gradient. Choice 2 of 7:TRUE - NADH in the matrix passes 2 e- to coenzyme Q via Complex I Choice 3 of 7: FALSE- only complex I contributes to matrix proton gradient ( pumping 4 Hydrogen ion across the membrane (matrix to intermembrane space). Choice 4 of 7: TRUE as 02 stabilizes the catalytically active conformation of Complex V. Choice 5 of 7: TRUE - Reversible protonation of c subunits leads to rotation of the Complex V gamma subunit. Choice 6 of 7:TRUE - Each B subunit can bind ATP tightly under the right conditions such as phosphorylation of ADP to produce ATP. Choice 7 of 7: FALSE - For every 2 protons that pass across the inner mitochondrial membrane, 1 ATP is produced.
Transcribed Image Text:Answer: Oxidative phosphorylation - It is a metabolic pathway and the electron donars transfer the electrons to the electron acceptors. The process takes place as redox reaction and the energy released is used for the generation of ATP. Choice 1 of 7: TRUE-Succinate contributes 2e- to Complex Il and 2H+ to the mitochondrial proton gradient. Choice 2 of 7:TRUE - NADH in the matrix passes 2 e- to coenzyme Q via Complex I Choice 3 of 7: FALSE- only complex I contributes to matrix proton gradient ( pumping 4 Hydrogen ion across the membrane (matrix to intermembrane space). Choice 4 of 7: TRUE as 02 stabilizes the catalytically active conformation of Complex V. Choice 5 of 7: TRUE - Reversible protonation of c subunits leads to rotation of the Complex V gamma subunit. Choice 6 of 7:TRUE - Each B subunit can bind ATP tightly under the right conditions such as phosphorylation of ADP to produce ATP. Choice 7 of 7: FALSE - For every 2 protons that pass across the inner mitochondrial membrane, 1 ATP is produced.
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