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Questions and Answers
What is the main function of oxidative phosphorylation?
Where does the Electron Transport Chain (ETC) take place?
Which complex in the Electron Transport Chain accepts electrons from ubiquinone to cytochrome c?
What is the final product when Complex IV (cytochrome a/a3) transfers electrons to O2?
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Which complexes in the Electron Transport Chain also act as proton translocating complexes?
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What is the main function of the Electron Transport Chain?
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Which inhibitor binds to Fe+3 in complex IV, preventing electron transfer to O2?
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Which ETC inhibitor displaces O2 by binding to hemoglobin?
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Which inhibitor results in a decrease in ATP synthesis by affecting the F0F1 compartment?
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Which inhibitor affects complex III in the Electron Transport Chain?
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Which inhibitor binds to Fe+2 in complex IV and also displaces O2 by binding to hemoglobin?
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What is the primary reason for cyanide being a deadly poison?
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Which inhibitor affects complex I in the Electron Transport Chain?
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What is the primary effect of chemical uncouplers like dinitrophenol (DNP) and dinitro cresol on the electron transport chain?
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Where is thermogenin, a physiological uncoupler, found in the body?
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In which cells is the pentose phosphate pathway (hexose monophosphate shunt) most active?
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What is the main function of uncouplers in the electron transport chain?
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What is the primary effect of physiological uncouplers like thermogenin on energy balance?
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How do chemical uncouplers affect the inner mitochondrial membrane permeability to protons?
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What is the primary effect of dinitrophenol (DNP) and dinitro cresol, as chemical uncouplers, on the electron transport chain?
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What is the primary function of uncouplers in the presence of electron transport?
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What is the primary effect of chemical uncouplers on the inner mitochondrial membrane permeability to protons?
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What is the primary function of NADPH in RBCs?
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Which process requires a sufficient level of NADPH for maintaining reduced glutathione?
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What is one of the major functions of NADPH in cellular metabolism?
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Which process requires a sufficient level of NADPH for maintaining reduced glutathione?
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What is the prevalence of G6PD deficiency highest in?
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What is the recommended approach for treating G6PD deficiency?
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Which gender is more susceptible to hemolytic anemia in G6PD deficiency?
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What is the recommended approach for treating G6PD deficiency?
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Which of the following is a triggering factor for hemolytic anemia in individuals with G6PD deficiency?
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During fasting (post-absorptive) state, which of the following is true about the liver's metabolic activity?
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What is the primary metabolic response of adipose tissue during an overnight fast?
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What is the primary metabolic response of adipose tissue during an overnight fast?
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In the fasting (post-absorptive) state, what is the primary metabolic activity of the liver?
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What is the effect of glucagon and epinephrine during an overnight fast?
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What is the primary source of energy for the brain after several weeks of fasting?
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During prolonged fasting, which cells continue to use glucose as their primary source of energy?
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What are the primary hormones that markedly increase levels during prolonged fasting (starvation), leading to lipolysis and ketone formation?
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What is the primary energy source for red blood cells during prolonged fasting?
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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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Description
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.
