Oxidative phosphorylation and PPP
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Questions and Answers

What is the main function of oxidative phosphorylation?

  • To convert glucose into ATP and GTP
  • To transfer energy to ATP and GTP molecules
  • To produce ATP by phosphorylating ADP (correct)
  • To carry out oxidation of NADPH and FADH2 in the electron transport chain

    • Where does the Electron Transport Chain (ETC) take place?

  • Inner mitochondrial membrane (correct)
  • Outer mitochondrial membrane
  • Endoplasmic reticulum
  • Cytosol

    • Which complex in the Electron Transport Chain accepts electrons from ubiquinone to cytochrome c?

  • Complex IV (cytochrome a/a3)
  • Complex I: NADH dehydrogenase
  • Complex II: Succinyl dehydrogenase
  • Complex III (cytochrome bc1) (correct)

    • What is the final product when Complex IV (cytochrome a/a3) transfers electrons to O2?

    <p>Water (H2O)</p> Signup and view all the answers

    Which complexes in the Electron Transport Chain also act as proton translocating complexes?

    <p>Complexes I, III, and IV</p> Signup and view all the answers

    What is the main function of the Electron Transport Chain?

    <p>Production of ATP</p> Signup and view all the answers

    Which inhibitor binds to Fe+3 in complex IV, preventing electron transfer to O2?

    <p>Cyanide</p> Signup and view all the answers

    Which ETC inhibitor displaces O2 by binding to hemoglobin?

    <p>Carbon monoxide</p> Signup and view all the answers

    Which inhibitor results in a decrease in ATP synthesis by affecting the F0F1 compartment?

    <p>Oligomycin</p> Signup and view all the answers

    Which inhibitor affects complex III in the Electron Transport Chain?

    <p>Antimycin A</p> Signup and view all the answers

    Which inhibitor binds to Fe+2 in complex IV and also displaces O2 by binding to hemoglobin?

    <p>Carbon monoxide</p> Signup and view all the answers

    What is the primary reason for cyanide being a deadly poison?

    <p>It binds Fe+3 in complex IV, preventing electron transfer to O2</p> Signup and view all the answers

    Which inhibitor affects complex I in the Electron Transport Chain?

    <p>Rotenone</p> Signup and view all the answers

    What is the primary effect of chemical uncouplers like dinitrophenol (DNP) and dinitro cresol on the electron transport chain?

    <p>Increase oxygen consumption and decrease ATP synthesis</p> Signup and view all the answers

    Where is thermogenin, a physiological uncoupler, found in the body?

    <p>Brown adipose tissue</p> Signup and view all the answers

    In which cells is the pentose phosphate pathway (hexose monophosphate shunt) most active?

    <p>Erythrocytes, liver, and adipose tissue</p> Signup and view all the answers

    What is the main function of uncouplers in the electron transport chain?

    <p>To dissipate energy as heat by uncoupling electron transport from ATP synthesis</p> Signup and view all the answers

    What is the primary effect of physiological uncouplers like thermogenin on energy balance?

    <p>Allowing energy loss as heat to maintain body temperature</p> Signup and view all the answers

    How do chemical uncouplers affect the inner mitochondrial membrane permeability to protons?

    <p>Increase permeability to protons</p> Signup and view all the answers

    What is the primary effect of dinitrophenol (DNP) and dinitro cresol, as chemical uncouplers, on the electron transport chain?

    <p>Increase oxygen consumption and dissipate energy as heat</p> Signup and view all the answers

    What is the primary function of uncouplers in the presence of electron transport?

    <p>Dissipate energy as heat without ATP synthesis</p> Signup and view all the answers

    What is the primary effect of chemical uncouplers on the inner mitochondrial membrane permeability to protons?

    <p>Increase permeability, allowing proton flow and halting ATP synthesis</p> Signup and view all the answers

    What is the primary function of NADPH in RBCs?

    <p>Detoxification of reactive oxygen species</p> Signup and view all the answers

    Which process requires a sufficient level of NADPH for maintaining reduced glutathione?

    <p>Detoxification reactions</p> Signup and view all the answers

    What is one of the major functions of NADPH in cellular metabolism?

    <p>Biosynthesis of fatty acids and steroid hormones</p> Signup and view all the answers

    Which process requires a sufficient level of NADPH for maintaining reduced glutathione?

    <p>Detoxification of reactive oxygen species</p> Signup and view all the answers

    What is the prevalence of G6PD deficiency highest in?

    <p>Middle East, tropical Africa, and Asia</p> Signup and view all the answers

    What is the recommended approach for treating G6PD deficiency?

    <p>Avoiding known triggers</p> Signup and view all the answers

    Which gender is more susceptible to hemolytic anemia in G6PD deficiency?

    <p>Men</p> Signup and view all the answers

    What is the recommended approach for treating G6PD deficiency?

    <p>Avoiding known triggers</p> Signup and view all the answers

    Which of the following is a triggering factor for hemolytic anemia in individuals with G6PD deficiency?

    <p>Ingestion of fava beans (favism)</p> Signup and view all the answers

    During fasting (post-absorptive) state, which of the following is true about the liver's metabolic activity?

    <p>Glycogenolysis and gluconeogenesis are increased</p> Signup and view all the answers

    What is the primary metabolic response of adipose tissue during an overnight fast?

    <p>Release of fatty acids</p> Signup and view all the answers

    What is the primary metabolic response of adipose tissue during an overnight fast?

    <p>Release of fatty acids</p> Signup and view all the answers

    In the fasting (post-absorptive) state, what is the primary metabolic activity of the liver?

    <p>Glycogenolysis and gluconeogenesis</p> Signup and view all the answers

    What is the effect of glucagon and epinephrine during an overnight fast?

    <p>Promote release of glucose from liver glycogen stores</p> Signup and view all the answers

    What is the primary source of energy for the brain after several weeks of fasting?

    <p>Ketone bodies</p> Signup and view all the answers

    During prolonged fasting, which cells continue to use glucose as their primary source of energy?

    <p>Red blood cells (RBCs)</p> Signup and view all the answers

    What are the primary hormones that markedly increase levels during prolonged fasting (starvation), leading to lipolysis and ketone formation?

    <p>Glucagon and epinephrine</p> Signup and view all the answers

    What is the primary energy source for red blood cells during prolonged fasting?

    <p>Glucose</p> Signup and view all the answers

    Study Notes

    • Oxidative Phosphorylation is the final pathway in aerobic cells where electrons derived from various substrates are liberated to oxygen, reducing it to water, and the energy is used for phosphorylation of ADP to ATP.
    • The Electron Transport Chain (ETC) is the pathway responsible for the oxidation of NADH and FADH2, and the phosphorylation of ADP to ATP in the mitochondria.
    • The ETC is located in the inner mitochondrial membrane and is composed of four complexes: I, II, III, and IV.
    • Complex I (NADH dehydrogenase) and Complex II (succinyl dehydrogenase) transfer electrons from NADH and FADH2 to coenzyme Q, respectively.
    • Complex III (cytochrome bc1) and Complex IV (cytochrome a/a3) or cytochrome oxidase, accept electrons from ubiquinone and cytochrome c, and transfer them to oxygen, forming water.
    • Three of the complexes, I, III, and IV, are proton translocating complexes that use the free energy from electron transport to move protons from the inside to the outside of the inner mitochondrial membrane, creating a proton motive force (p.m.f).
    • Inhibitors of the ETC and oxidative phosphorylation, like cyanide and carbon monoxide, decrease oxygen consumption, increase intracellular NADH/NAD and FADH2/FAD ratio, and decrease ATP production.
    • Uncouplers, like dinitrophenol and dinitro cresol, increase the permeability of the inner mitochondrial membrane to protons, allowing electron flow to continue, but stopping ATP synthesis, and increasing oxygen consumption and the oxidation of NADH and FADH2.
    • The Pentose Phosphate Pathway (PPP) is a metabolic pathway that occurs in the cytoplasm of every cell, but is most active in the erythrocytes, liver, and adipose tissue.
    • The PPP has two major functions: (1) the formation of NADPH, a reducing agent, and (2) the synthesis of ribose for nucleotide and nucleic acid formation (DNA and RNA).
    • NADPH has important functions, including the biosynthesis of fatty acids and steroid hormones, and the maintenance of a supply of reduced glutathione to protect against reactive oxygen species (ROS).
    • G6PD deficiency is an X-linked recessive inborn error of metabolism that affects the erythrocytes, causing a hemolytic anemia, neonatal jaundice, and is most prevalent in the Middle East, tropical Africa, and Asia.
    • The most common triggering factors for G6PD deficiency hemolytic anemia are oxidant drugs (AAA), fava beans (favism), and infections.
    • In the fasting state, there is an increase in glucagon and epinephrine levels, resulting in glycogenolysis, gluconeogenesis, amino acid release from skeletal muscles, and fatty acid release from adipose tissue.
    • During prolonged fasting, the brain adapts to using ketone bodies as a source of energy, while the RBCs continue to use glucose. Lipolysis results in the formation of acetyl-CoA, which is then converted to ketones, and the brain uses two-thirds ketones and one-third glucose as a source of energy after several weeks of fasting.

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    Test your knowledge on the process of oxidative phosphorylation and the production of ATP from NADH and FADH2. Explore how energy is harnessed and utilized in the electron transport chain.

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