Oxidative Phosphorylation Overview
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Questions and Answers

What is the primary function of Complex III in the electron transport chain?

  • To generate ATP directly
  • To reduce oxygen into water
  • To oxidize cytochrome c
  • To translocate additional protons to the intermembrane space (correct)

    • In what form of oxidation state can heme iron in cytochrome c exist?

  • Both ferrous (Fe3+) and ferric (Fe2+) (correct)
  • Neither ferrous nor ferric
  • Only ferrous (Fe3+)
  • Only ferric (Fe2+)

    • What is cytochrome c's role in the electron transport process?

  • It reduces ubiquinone to QH2
  • It carries a single electron from the cytochrome bc1 complex to cytochrome oxidase (correct)
  • It oxidizes oxygen to form water
  • It generates protons in the matrix

    • Which of the following components are found in mammalian cytochrome oxidase?

    <p>Copper ions and heme groups</p> Signup and view all the answers

    How many protons are picked up from the matrix during the process of reducing one molecule of oxygen in Complex IV?

    <p>Four protons</p> Signup and view all the answers

    What are the main reduced fuels that provide energy for ATP synthesis in cellular respiration?

    <p>Carbohydrates, lipids, and amino acids</p> Signup and view all the answers

    What role do NADH and FADH2 play in oxidative phosphorylation?

    <p>They act as electron donors in ATP synthesis.</p> Signup and view all the answers

    How is the energy required to convert ADP to ATP in oxidative phosphorylation provided?

    <p>From the flow of protons down the electrochemical gradient</p> Signup and view all the answers

    Which of the following structures is NOT a component of a mitochondrion?

    <p>Cell wall</p> Signup and view all the answers

    What is the significance of the cristae within the inner membrane of a mitochondrion?

    <p>They increase surface area for electron transport chain complexes.</p> Signup and view all the answers

    Which theory explains the coupling of electron flow with proton movement to produce ATP?

    <p>Mitchell's Chemiosmotic Theory</p> Signup and view all the answers

    Which component of the mitochondrion has the highest proton concentration during oxidative phosphorylation?

    <p>Intermembrane space</p> Signup and view all the answers

    Which mechanism primarily drives the transport of protons against the electrochemical gradient in mitochondria?

    <p>Coupling with electron transport chain reactions</p> Signup and view all the answers

    What is the total amount of ATP produced using the Malate Shuttle?

    <p>38 ATP</p> Signup and view all the answers

    Which compounds primarily regulate the rate of oxidative phosphorylation?

    <p>NADH and ADP/Pi</p> Signup and view all the answers

    How many ATP are produced from the oxidation of 2 NADH during glycolysis using the Malate Shuttle?

    <p>6 ATP</p> Signup and view all the answers

    Which of the following is a measure of the energy status of a cell?

    <p>Mass-Action Ratio</p> Signup and view all the answers

    What happens to the Mass-Action Ratio when energy is required in the cell?

    <p>It decreases</p> Signup and view all the answers

    What effect does high ATP concentration have on oxidative phosphorylation?

    <p>Inhibits ATP production</p> Signup and view all the answers

    How many ATP are generated from the Krebs cycle per molecule of acetyl-CoA?

    <p>2 ATP</p> Signup and view all the answers

    How does the intracellular concentration of ADP influence respiration rates?

    <p>Decreases respiration rates when high</p> Signup and view all the answers

    What effect does the addition of cyanide (CN-) have on cellular respiration?

    <p>It inhibits respiration and ATP synthesis.</p> Signup and view all the answers

    Which molecule is a known uncoupler that allows respiration without ATP synthesis?

    <p>Dinitrophenol (DNP)</p> Signup and view all the answers

    What role does thermogenin play in brown adipose tissue?

    <p>It provides heat through H+ flow.</p> Signup and view all the answers

    What is the primary function of the Malate-Aspartate Shuttle?

    <p>To transport reducing equivalents (NADH) into the mitochondrial matrix.</p> Signup and view all the answers

    How does valinomycin contribute to the process of ATP synthesis?

    <p>It generates a K+ electrochemical gradient.</p> Signup and view all the answers

    What is a consequence of the action of oligomycin?

    <p>Inhibits ATP synthase activity.</p> Signup and view all the answers

    What is the end result of transferring reducing equivalents to the mitochondrial matrix via the Glycerol-3-Phosphate Shuttle?

    <p>Formation of FADH2, resulting in a loss of energy.</p> Signup and view all the answers

    What is required for the translocation of an additional proton per ATP synthesized?

    <p>Cotransport of substrates and products.</p> Signup and view all the answers

    What is primarily released from the mitochondria that triggers apoptosis?

    <p>Cytochrome c</p> Signup and view all the answers

    Which of the following is correct regarding mitochondrial DNA?

    <p>It is maternally inherited.</p> Signup and view all the answers

    What is a consequence of defects in oxidative phosphorylation?

    <p>Low ATP levels in the cell.</p> Signup and view all the answers

    Which process occurs in the mitochondria?

    <p>Protein synthesis using ribosomes</p> Signup and view all the answers

    What is the primary role of caspases in the cell?

    <p>Promoting apoptosis</p> Signup and view all the answers

    Which of the following best describes the genetic coding of mitochondrial proteins?

    <p>Most mitochondrial proteins are coded by nuclear DNA.</p> Signup and view all the answers

    What is the source of the proton motive force in mitochondria?

    <p>Electron transport chain activity</p> Signup and view all the answers

    Which of the following accurately describes the role of mitochondrial ribosomes?

    <p>They allow protein synthesis within mitochondria.</p> Signup and view all the answers

    What is the main role of Complex I in the electron transport chain?

    <p>To transfer two electrons from NADH to ubiquinone</p> Signup and view all the answers

    How much energy is produced when transporting a pair of electrons from NADH to O2?

    <p>220 kJ</p> Signup and view all the answers

    What happens to the four protons transported by NADH when it interacts with Complex I?

    <p>They are pumped into the intermembrane space</p> Signup and view all the answers

    What is one key characteristic of Succinate Dehydrogenase (Complex II)?

    <p>It has a dual role in both the citric acid cycle and electron transport chain</p> Signup and view all the answers

    What kind of reactions are involved in the transport of electrons through Complexes I to IV?

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

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

    <p>To bypass the H+ flow through ATPase</p> Signup and view all the answers

    What is the result of the energetic difference in redox potential during electron transfer?

    <p>Creation of a proton concentration gradient</p> Signup and view all the answers

    How many protons are transported into the intermembrane space for each NADH molecule processed by Complex I?

    <p>4 protons</p> Signup and view all the answers

    Study Notes

    Oxidative Phosphorylation Overview

    • Oxidative phosphorylation is a metabolic process that uses energy from NADH and FADH₂ to produce ATP.
    • Carbohydrates, lipids, and amino acids are the primary reduced fuels for the cell.
    • Electrons from reduced fuel molecules are transferred to cofactors NADH or FADH₂.

    Chemiosmotic Theory

    • Energy needed to phosphorylate ADP is provided by the flow of protons down the electrochemical gradient.
    • ∆G is related to ΔE = E₀ (e⁻ acceptor) – E₀ (e⁻ donor)
    • Electrons are transferred from lower (more negative) to higher (more positive) reduction potential.
    • Electrons released from redox processes, during electron transport transfer, power proton pumping against the electrochemical gradient.

    Chemiosmotic Energy Coupling

    • The proton gradient, necessary for ATP synthesis, is stably established across a membrane, impermeable to ions.
    • Membranes in mitochondria
    • inner membrane
    • thylakoid membrane in chloroplasts
    • plasma membrane in bacteria
    • Proteins in the membrane couple 'downhill' flow of electrons with 'uphill' flow of protons across the membrane
    • Another protein within the membrane couples the 'downhill' flow of protons to the phosphorylation of ADP.

    Electron Carriers in the Electron Transport Chain

    • Complexes in the electron transport chain contain multiple redox centers: flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD), cytochromes (a,b,c), and iron-sulfur clusters.
    • Electron transfer order depends on reduction potential.
    • These carriers have varying reduction potential (E'). Higher E' means greater tendency to accept electrons.

    Coenzymes (FAD/FMN, NAD+/NADH, and FAD/FADH₂)

    • Coenzymes associated with dehydrogenases transfer hydride ions (H⁻), consisting of one proton and two electrons.
    • NAD(P)+/NAD(P)H, FMN/FMNH2, and FAD/FADH₂ are important electron carriers.
    • FAD/FMN transfer hydrogen atoms (one proton and one electron)

    Coenzyme Q (Ubiquinone)

    • Lipid-soluble quinone, isoprenoid compound; readily accepts electrons from different redox-active compounds.
    • Accepts two electrons; picks up two protons to become ubiquinol.
    • Ubiquinol can diffuse freely in the membrane, carrying electrons with protons.
    • Coenzyme Q transports electrons from complexes I and II to Complex III.

    Cytochromes (a, b, and c)

    • One-electron carriers based on Fe³⁺/Fe²⁺ redox systems.
    • Cytochromes a, b, and c, differ by ring additions and substitutions, which affect their redox properties.

    Iron-Sulfur Proteins

    • One-electron carriers based on Fe³⁺/Fe²⁺ redox system.
    • Iron ions coordinated by cysteine residues in the protein.
    • Iron-sulfur clusters contain equal numbers of iron and sulfur atoms.

    Chemiosmotic Model for ATP Synthesis

    • Electron transport through complexes I-IV establishes a proton-motive force (PMF).
    • The energy of PMF drives ATP synthesis via ATP synthase.
    • Includes the flow of electrons creates a concentration gradient of protons established across the membrane.

    Mitochondrial ATP Synthase Complex

    • Consists of two functional subunits (Fo and F₁)
    • Fo is an integral membrane complex that transports protons from the intermembrane space to the matrix.
    • F₁ is a soluble complex in the matrix that hydrolyzes ATP.
    • Dimers, can exist in 3 different conformations (open, loose and tight).

    Synthesis of ATP in ATP Synthase

    • Translocation of 3 protons fuels synthesis of one ATP molecule
    • Electrochemical energy generated through proton concentration gradients drives ATP synthesis.

    Inhibitors and Uncouplers

    • Inhibitors block electron transport (e.g., cyanide, antimycin A).
    • Inhibitors block ATP synthase (e.g., oligomycin, venturicidin).
    • Uncouplers allow respiration to continue without ATP synthesis (e.g., dinitrophenol, valinomycin).
    • Uncouplers bypass H⁺ flow through the ATPase.

    Mitochondrial Transport of Species

    • Translocation of a fourth proton per ATP is required.
    • This allows cotransport of substrates into and products out of the matrix.
    • Adenine nucleotide translocase and phosphate translocase are important transport proteins in the inner mitochondrial membrane.

    Malate-Aspartate Shuttle

    • Transports reducing equivalents (NADH) from the cytosol into the mitochondrial matrix.
    • This shuttle is important in liver, kidneys, and heart.

    Glycerol-3-Phosphate Shuttle

    • An alternative method used by skeletal muscle and brain tissues to transport reducing equivalents.
    • Transfers electrons through FADH₂, reducing NADH production efficiency by one ATP generated per NADH molecule.

    Oxidation of Glucose

    • Oxidation of Glucose yields a total of 38 ATP molecules with the Malate Shuttle. With Glycerol Phosphate Shuttle the yield is 36 ATP.

    Regulation of Oxidative Phosphorylation

    • Primarily regulated by substrate availability (NADH and ADP/Pi).
    • The rate of O₂ consumption and ATP synthesis is regulated by the intracellular concentration of ADP.
    • High ATP levels inhibit oxidative phosphorylation.

    Mitochondria and Apoptosis

    • Mitochondrial membrane integrity loss during apoptosis (programmed cell death) releases cytochrome c that activates caspase proteases.

    Mitochondrial Genetics

    • Mitochondrial DNA (mtDNA) is circular and carries 37 genes.
    • mtDNA encodes rRNA, tRNA molecules, and enzymes critical to oxidative phosphorylation.
    • Mitochondria have their own ribosomes but rely on nuclear DNA for most proteins.
    • mtDNA inheritance is maternal.
    • Mutations in mitochondrial DNA can produce various diseases.

    Mitochondrial Mutations and Diabetes

    • Defects in oxidative phosphorylation can reduce ATP production.
    • This causes impaired insulin release from pancreatic beta cells which leads to a rare form of diabetes.

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    Oxidative Phosphorylation - Chapter 19 PDF

    Description

    This quiz covers the key concepts of oxidative phosphorylation, including the role of NADH, FADH₂, and the chemiosmotic theory. Understand how energy is harnessed to synthesize ATP through the flow of protons and electron transfer. Test your knowledge on the metabolic processes underlying cellular respiration.

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