WorksheetsTheories of Oxidative Phosphorylation Overview
Total questions: 20
Worksheet time: 10mins
If antimycin A is added to respiring mitochondria, what immediate change is expected?
Electron flow from ubiquinol to cytochrome c stops
Electrons from NADH reduce ubiquinone faster
Oxygen consumption increases markedly
Complex II activity bypasses Complex III fully
Blocking succinate dehydrogenase would most directly reduce which downstream component’s reduction state?
Ubiquinone receiving electrons from FADH2
Cytochrome c at the intermembrane space
NADH binding site on Complex I
Oxygen at the terminal oxidase
Which combination correctly pairs Complex and one representative inhibitor?
Complex II – TTFA
Complex III – Rotenone
Complex I – Malonate
Complex IV – Myxothiazol
A lab notes azide rapidly halts ATP synthesis despite normal substrates. What is the most direct site of action?
Cytochrome c oxidase at Complex IV
NADH dehydrogenase at Complex I
Succinate dehydrogenase at Complex II
Cytochrome bc1 at Complex III
Which statement best describes how chemical uncouplers affect oxidative phosphorylation in mitochondria?
They allow electron transport but dissipate proton motive force
They inhibit electron flow at Complex IV completely
They increase ATP yield by strengthening proton gradient
They block NADH oxidation while preserving ATP synthesis
Which pair correctly matches both items from the uncoupler list?
Valinomycin and Nigericin
Glucose and Pyruvate
Cytochrome c and NADH
ATP and ADP
Which listed compound is not an ionophore?
Dinitro cresol
Valinomycin
Nigericin
None of these
Select the compound that would most likely disrupt the proton gradient by shuttling ions, consistent with being lipophilic.
Valinomycin
Glutamate
Water
Phosphate
Which statement best explains why these compounds act as uncouplers?
Their lipophilicity allows membrane transport
They donate electrons to Complex IV
They inhibit ATP synthase binding
They increase mitochondrial DNA replication
Which chemical name in the list most clearly indicates multiple chlorine substitutions on phenol?
Penta chloro phenol
Dinitro cresol
Bilirubin
Thyroxine
A researcher wants a K+ carrier to collapse membrane potential. Which listed compound fits best?
Valinomycin
Bilirubin
Thyroxine
Penta chloro phenol
In the diagram, 2,4-dinitrophenol (DNP) shuttles across the membrane between low-pH and high-pH sides. Which statement best explains how this uncouples oxidative phosphorylation?
It carries protons across the membrane, collapsing the proton gradient
It inhibits electron flow through Complex IV directly and permanently
It binds ATP synthase catalytic sites, preventing ADP from binding
It increases inner membrane permeability to NADH and FADH2
At toxic high doses, aspirin most directly causes which cellular effect?
Uncoupling oxidative phosphorylation
Blocking complex I electron transfer
Irreversibly inhibiting ATP synthase
Stimulating cytochrome c oxidase
Which statement about thyroid hormone excess and mitochondria is most accurate?
It increases uncoupling, raising basal heat
It blocks ATP synthase, lowering heat
It inhibits electron flow, lowering oxygen
It lowers proton leak, reducing heat
Which patient presentation most aligns with salicylate uncoupling toxicity?
Hyperthermia with tachypnea
Profound bradycardia only
Hypothermia with sedation
Hypertension without fever
Which cellular outcome is expected when oxidative phosphorylation is uncoupled?
ATP synthesis drops as heat rises
ATP synthesis rises as heat falls
Both ATP and heat generation rise
Electron transport halts completely
Which phrase completes the idea: Physiological uncouplers primarily act by...?
Dissipating the proton motive force
Blocking ADP binding to ATPase
Oxidizing NADH to NAD+ directly
Inhibiting cytochrome oxidase
In what condition might neonatal mitochondria be at risk due to bilirubin?
Severe unconjugated hyperbilirubinaemia
Mild conjugated hyperbilirubinaemia
Resolved physiological jaundice only
Bilirubin bound to albumin strongly
Which metabolic consequence follows thyroid hormone–induced uncoupling?
Higher basal metabolic rate
Lower basal metabolic rate
No change in heat production
Complete ATP synthesis arrest
Which condition is least likely to act as a physiological uncoupler?
Conjugated hyperbilirubinaemia state
Thyroid hormone excess state
Unconjugated bilirubin excess
High-dose salicylate exposure
