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Questions and Answers
Where does the citric acid cycle primarily take place?
Where does the citric acid cycle primarily take place?
Which of the following is NOT a type of electron carrier found in the electron-transport chain complexes?
Which of the following is NOT a type of electron carrier found in the electron-transport chain complexes?
What is the primary function of coenzyme Q (ubiquinone) in the electron transport chain?
What is the primary function of coenzyme Q (ubiquinone) in the electron transport chain?
Which deficiency is associated with a lack of hydride ion transfer?
Which deficiency is associated with a lack of hydride ion transfer?
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What is the impact when ubiquinone accepts two electrons?
What is the impact when ubiquinone accepts two electrons?
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What is the main purpose of oxidative phosphorylation in cellular respiration?
What is the main purpose of oxidative phosphorylation in cellular respiration?
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What is the significance of the proton gradient in oxidative phosphorylation?
What is the significance of the proton gradient in oxidative phosphorylation?
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What role does the inner membrane of mitochondria play?
What role does the inner membrane of mitochondria play?
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Which of the following statements about the outer membrane of mitochondria is true?
Which of the following statements about the outer membrane of mitochondria is true?
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What did Peter Mitchell contribute to the understanding of oxidative phosphorylation?
What did Peter Mitchell contribute to the understanding of oxidative phosphorylation?
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How is energy released by electron transport utilized in oxidative phosphorylation?
How is energy released by electron transport utilized in oxidative phosphorylation?
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What would happen if the membranes involved in chemiosmotic energy coupling were not present?
What would happen if the membranes involved in chemiosmotic energy coupling were not present?
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Which compartment of the mitochondrion has a higher concentration of protons?
Which compartment of the mitochondrion has a higher concentration of protons?
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What is the primary function of Cytochromes in the electron transport chain?
What is the primary function of Cytochromes in the electron transport chain?
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Which of the following statements about iron-sulfur proteins is true?
Which of the following statements about iron-sulfur proteins is true?
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What role does the chemiosmotic model play in ATP synthesis?
What role does the chemiosmotic model play in ATP synthesis?
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Which enzyme complex identified in the mitochondrial respiratory chain has the highest mass?
Which enzyme complex identified in the mitochondrial respiratory chain has the highest mass?
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How does the number of subunits in the human cytochrome c compare to that of other complexes?
How does the number of subunits in the human cytochrome c compare to that of other complexes?
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What is the primary prosthetic group found in Succinate dehydrogenase?
What is the primary prosthetic group found in Succinate dehydrogenase?
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Which components are part of the prosthetic groups in Ubiquinone: cytochrome c oxidoreductase?
Which components are part of the prosthetic groups in Ubiquinone: cytochrome c oxidoreductase?
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What distinct feature is observed in the structure of iron-sulfur clusters?
What distinct feature is observed in the structure of iron-sulfur clusters?
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What effect does the addition of cyanide (CN-) have on cellular respiration?
What effect does the addition of cyanide (CN-) have on cellular respiration?
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How do venturicidin and oligomycin affect ATP synthesis?
How do venturicidin and oligomycin affect ATP synthesis?
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What is the primary function of uncouplers like dinitrophenol (DNP)?
What is the primary function of uncouplers like dinitrophenol (DNP)?
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What role does valinomycin play in mitochondrial function?
What role does valinomycin play in mitochondrial function?
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What physiological role does thermogenin play in brown adipose tissue?
What physiological role does thermogenin play in brown adipose tissue?
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What is the result of using the malate-aspartate shuttle in the liver, kidneys, and heart?
What is the result of using the malate-aspartate shuttle in the liver, kidneys, and heart?
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How does the glycerol-3-phosphate shuttle differ from the malate-aspartate shuttle?
How does the glycerol-3-phosphate shuttle differ from the malate-aspartate shuttle?
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What is a consequence of the proton gradient established across the mitochondrial membrane?
What is a consequence of the proton gradient established across the mitochondrial membrane?
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What triggers the activation of caspases during apoptosis?
What triggers the activation of caspases during apoptosis?
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What is the inheritance pattern of mitochondrial DNA?
What is the inheritance pattern of mitochondrial DNA?
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Which of the following is primarily synthesized in the cytosol and then imported into the mitochondria?
Which of the following is primarily synthesized in the cytosol and then imported into the mitochondria?
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What condition is characterized by defects in oxidative phosphorylation leading to low ATP levels?
What condition is characterized by defects in oxidative phosphorylation leading to low ATP levels?
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What is the primary measure of the energy status of a cell during oxidative phosphorylation?
What is the primary measure of the energy status of a cell during oxidative phosphorylation?
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How is the proton motive force created in mitochondria?
How is the proton motive force created in mitochondria?
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Which is one of the key roles of ribosomes found in mitochondria?
Which is one of the key roles of ribosomes found in mitochondria?
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Which compound is produced during the conversion of pyruvate to acetyl-CoA?
Which compound is produced during the conversion of pyruvate to acetyl-CoA?
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What is the primary function of ATP in the cell?
What is the primary function of ATP in the cell?
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What is the total ATP yield when using the Malate Shuttle?
What is the total ATP yield when using the Malate Shuttle?
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Which process is directly linked to the failure of mitochondria in insulin release?
Which process is directly linked to the failure of mitochondria in insulin release?
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How is the rate of ATP synthesis primarily regulated during oxidative phosphorylation?
How is the rate of ATP synthesis primarily regulated during oxidative phosphorylation?
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Which of the following correctly describes the effect of high ATP concentrations on oxidative phosphorylation?
Which of the following correctly describes the effect of high ATP concentrations on oxidative phosphorylation?
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What is the role of the Mass-Action Ratio in ATP synthesis?
What is the role of the Mass-Action Ratio in ATP synthesis?
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Which intermediate is derived from citrate during the Krebs cycle?
Which intermediate is derived from citrate during the Krebs cycle?
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What is the outcome of the reaction catalyzed by FAD in the Krebs cycle?
What is the outcome of the reaction catalyzed by FAD in the Krebs cycle?
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Study Notes
Oxidative Phosphorylation Overview
- Oxidative phosphorylation harnesses energy from NADH and FADH₂ to produce ATP.
- Carbohydrates, lipids, and amino acids are the primary reduced fuels for the cell.
- Electrons from reduced fuels are transferred to NADH or FADH₂ cofactors.
Chemiosmotic Theory
- Energy needed to phosphorylate ADP comes from protons flowing down an electrochemical gradient.
- ΔG is directly related to ΔE = Eo (e⁻ acceptor) – Eo (e⁻ donor).
- ΔG = - ηIΔE, where T = 298°K = 25°C, R = 8.315 J/mol·K, η = # electrons transferred per molecule, J = 96.48 kJ/V·mol (Faraday).
Chemiosmotic Energy Coupling
- Proton gradient needed for ATP synthesis is established across membranes impermeable to ions.
- These include the plasma membrane in bacteria, inner membrane in mitochondria, and thylakoid membrane in chloroplasts.
- Membranes must contain proteins to couple electron flow (downhill) with proton flow (uphill) across the membrane.
- A protein couples the downhill flow of protons to the phosphorylation of ADP.
Structure of Mitochondrion
- Double membrane creates four distinct compartments:
- Outer membrane: relatively porous, permeable to small molecules.
- Intermembrane space (IMS): Similar environment to cytosol, with higher proton concentration (lower pH).
- Inner membrane: Impermeable, with proton gradient across it. Contains complexes of electron transport chain and cristae to increase surface area.
- Matrix: Contains citric acid cycle enzymes, fatty acid oxidation enzymes, amino acid oxidation enzymes, DNA, ribosomes, etc. Lower proton concentration (higher pH).
Electron Transport Chain Complexes
- Each complex contains multiple redox centers, including flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD), cytochromes (a, b, or c), and iron-sulfur clusters.
- Electron transfer order depends on reduction potential.
Coenzymes as Electron Carriers
- Coenzymes associated with dehydrogenases transfer hydride ions (H⁻, one proton plus two electrons).
- NAD+/NADH, FMN/FMNH₂, FAD/FADH₂ are important coenzymes.
Coenzyme Q (Ubiquinone)
- Lipid-soluble quinone isoprenoid compound, readily accepting electrons from different redox-active compounds.
- Accepts two electrons, picks up two protons to become ubiquinol.
- Freely diffuses, carrying electrons with protons across the membrane.
- Mobile electron carrier, transporting electrons from Complexes I and II to Complex III.
Cytochromes
- Composed of Fe³⁺/Fe²⁺ redox system and heme derivatives (a, b, or c). Ring additions/substitutions affect redox properties.
- One-electron carriers.
Iron-Sulfur Proteins
- One-electron carriers based on Fe³⁺/Fe²⁺ redox system.
- Iron ions coordinated by cysteine in proteins or as iron-sulfur clusters.
- Iron-sulfur clusters have equal numbers of iron and sulfur atoms.
Chemiosmotic Model for ATP Synthesis
- Electron transport through complexes I-IV creates a proton-motive force (proton gradient).
- Energy of proton-motive force drives ATP synthesis.
Mitochondrial ATP Synthase Complex
- Composed of two functional units, Fo and F₁.
- Fo is the integral membrane complex that transports protons dissipating the proton gradient.
- F₁ is the soluble complex in matrix catalyzing ATP hydrolysis and creation.
- Dimers exist in different conformations (open, loose, tight).
Synthesis of ATP in ATP Synthase
- Translocation of three protons fuels synthesis of one ATP.
Inhibitors
- Cyanide (CN⁻), carbon monoxide, antimycin A, myxothiazol, rotenone, amytal, piericidin A, DCMU, oligomycin, venturicidin, DCCD, FCCP, DNP, valinomycin, and atractyloside interfere with the process.
Transport of Different Species in/Out of Matrix
- Proton translocation facilitates cotransport of substrates into and products out of the mitochondria.
Malate-Aspartate Shuttle
- This shuttle transports reducing equivalents (NADH) from cytosol into the mitochondrial matrix.
Glycerol-3-Phosphate Shuttle
- An alternative mechanism for shuttling reducing equivalents (NADH) from cytosol to the mitochondrial matrix. This process results in the formation of FADH₂, rather than NADH, resulting in a lower energy yield (1 ATP less per NADH)
Regulation of Oxidative Phosphorylation
- Primarily regulated by substrate availability (NADH and ADP/Pi).
- Rate of O₂ consumption regulated by the amount of ADP/Pi.
- High ATP levels cause feedback inhibition Cascade up to PFK-1.
Mitochondria and Apoptosis
- Loss of mitochondrial membrane integrity releases cytochrome c, initiating apoptosis (programmed cell death).
Mitochondrial Genetics
- Mitochondrial DNA is circular and encodes rRNA, tRNA, and enzymes of central metabolism.
- Mitochondria have their own ribosomes for protein synthesis.
- Mitochondrial DNA is maternally inherited.
Mitochondrial Mutations and Diabetes
- Defects in oxidative phosphorylation result in low ATP, inhibiting correct insulin release from pancreatic β cells.
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Description
This quiz explores the key concepts of oxidative phosphorylation, including the role of NADH and FADH₂ in ATP production. Learn about the chemiosmotic theory and how protons flow to generate energy. Understand the coupling of electron and proton flow in various cellular membranes.
