Electron Transport Chain (ETC) and Oxidative Phosphorylation: Flashcards
(20 cards)
What molecule accumulates when Complex I of the electron transport chain is inhibited?
NADH
NADH donates electrons to Complex I; if Complex I is blocked, NADH cannot be oxidized and will accumulate.
What does oligomycin toxicity cause an increase in?
Proton gradient across the inner mitochondrial membrane
Oligomycin blocks ATP synthase, causing protons to accumulate in the intermembrane space.
How do uncoupling agents like 2,4-DNP increase heat production?
Stimulate oxygen consumption without ATP synthesis
Uncouplers dissipate the proton gradient, increasing electron flow and heat production without making ATP.
Which enzyme complex is directly inhibited by cyanide?
Complex IV
Cyanide inhibits cytochrome oxidase (Complex IV), blocking electron transfer to oxygen.
Which molecule donates electrons to Complex II?
FADH₂
FADH₂ donates electrons to Complex II (succinate dehydrogenase).
What is the role of ATP synthase?
Couples proton flow to ATP synthesis
ATP synthase uses the proton gradient to generate ATP.
What happens to oxygen consumption and ATP levels when a patient is exposed to a mitochondrial uncoupler?
Elevated oxygen consumption but low ATP levels
Uncouplers allow protons to flow back without going through ATP synthase.
Where is cytochrome c located in the mitochondria?
Inner membrane space
Cytochrome c is loosely associated with the inner membrane, facing the intermembrane space.
What is the final electron acceptor in oxidative phosphorylation?
Oxygen
Oxygen accepts electrons at Complex IV and forms water.
Rotenone poisoning inhibits ATP generation from which electron donor?
NADH
Rotenone blocks Complex I, preventing NADH oxidation.
Which molecule activates pyruvate carboxylase during a 3-day fast?
Acetyl-CoA
Acetyl-CoA from beta-oxidation activates pyruvate carboxylase in fasting.
Which substrate cannot be used for gluconeogenesis?
Acetyl-CoA
Acetyl-CoA cannot generate net glucose due to its entry point in the TCA cycle.
High levels of fructose-2,6-bisphosphate would most likely result in increased:
Glycolysis
Fructose-2,6-bisphosphate activates PFK-1, promoting glycolysis.
Which gluconeogenic enzyme is found exclusively in the endoplasmic reticulum of hepatocytes?
Glucose-6-phosphatase
Glucose-6-phosphatase is localized to the ER membrane.
What energy source does the brain adapt to use after prolonged fasting?
Ketone bodies
Brain uses ketone bodies after about 3 days of fasting.
What enzyme is deficient in patients with impaired gluconeogenesis who cannot convert pyruvate into oxaloacetate?
Pyruvate carboxylase
Pyruvate carboxylase catalyzes the conversion of pyruvate to oxaloacetate.
Why is beta-oxidation necessary for gluconeogenesis?
Supplies energy (ATP) and acetyl-CoA
Beta-oxidation provides both energy and acetyl-CoA to activate gluconeogenesis.
Which enzyme is upregulated during gluconeogenesis due to low insulin and high glucagon?
Phosphoenolpyruvate carboxykinase
PEPCK is induced by glucagon and inhibited by insulin.
During gluconeogenesis, oxaloacetate must be converted into malate in order to:
Cross the mitochondrial membrane
Oxaloacetate cannot cross the inner membrane; it is reduced to malate first.
An increase in AMP levels in hepatocytes during fasting would most likely:
Inhibit gluconeogenesis
High AMP indicates low energy, which inhibits gluconeogenesis and favors energy production.
