Mitochondrial Function and Evolution
48 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of oxidative phosphorylation in aerobic organisms?

  • Conversion of energy to heat
  • Storage of carbohydrates
  • Decomposing nucleic acids
  • Synthesis of ATP (correct)

    • Oxidative phosphorylation occurs only in prokaryotic cells.

    False

    What major evolutionary event led to the origin of mitochondria?

    Endosymbiotic relationship with bacteria

    The final electron acceptor in the mitochondrial respiratory chain is __________.

    <p>molecular oxygen</p> Signup and view all the answers

    Which process is NOT associated with mitochondrial function?

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

    Match the mitochondrial functions to their descriptions:

    <p>ATP Synthesis = Production of cellular energy Thermogenesis = Heat production Apoptosis = Programmed cell death Fatty acid oxidation = Breakdown of fats for energy</p> Signup and view all the answers

    The appearance of oxygen in the atmosphere around 2.3 billion years ago was crucial for the evolution of more complex life forms.

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

    In eukaryotes, where does oxidative phosphorylation take place?

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

    What is the typical size range of mitochondria?

    <p>1 to 10 μm</p> Signup and view all the answers

    Mitochondria contain enzymes for glycolysis.

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

    What types of fuels do the pathways in the mitochondrial matrix oxidize?

    <p>Pyruvate, fatty acids, and amino acids</p> Signup and view all the answers

    The __________ is a selectively permeable membrane that segregates metabolic pathways.

    <p>inner mitochondrial membrane</p> Signup and view all the answers

    What percentage of proteins in mammalian mitochondria are currently enigmatic in function?

    <p>25%</p> Signup and view all the answers

    Match the following tissues with their mitochondrial demand:

    <p>Brain = High demand for aerobic metabolism Skeletal Muscle = High demand for aerobic metabolism Skin = Low demand for aerobic metabolism Liver = High demand for aerobic metabolism</p> Signup and view all the answers

    What cellular process allows mitochondria to divide?

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

    Mitochondria can fuse under certain circumstances.

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

    What function is associated with Complex II in the citric acid cycle?

    <p>Conversion of succinate to fumarate</p> Signup and view all the answers

    Heme b in Complex II is in the direct path of electron transfer.

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

    What is the primary consequence of mutations in Complex II subunits near heme b?

    <p>Increased production of reactive oxygen species (ROS)</p> Signup and view all the answers

    The binding site for succinate is located in subunit __ of Complex II.

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

    Match the following components of Complex II with their functions:

    <p>Heme b = Reduces electron leakage FAD = Initial electron acceptor Iron-sulfur centers = Transfer electrons to ubiquinone Ubiquinone = Final electron acceptor in Complex II</p> Signup and view all the answers

    Individuals with hereditary paraganglioma typically have mutations near which site in Complex II?

    <p>Ubiquinone-binding site</p> Signup and view all the answers

    Complex II solely impacts the citric acid cycle without any relation to mitochondrial electron transfer.

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

    What are the reactive oxygen species (ROS) produced when electrons leak from the system?

    <p>Hydrogen peroxide (H2O2) and superoxide radical (·O2−)</p> Signup and view all the answers

    What is Complex III also known as?

    <p>Ubiquinone:cytochrome c oxidoreductase</p> Signup and view all the answers

    Complex III consists of a single monomer.

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

    Name one of the proteins central to the action of Complex III.

    <p>Cytochrome b, cytochrome c, or the Rieske iron-sulfur protein</p> Signup and view all the answers

    The functional core of each monomer of Complex III consists of three subunits: cytochrome b, the Rieske iron-sulfur protein, and ___ .

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

    Which sites on Complex III correspond to its ubiquinone binding sites?

    <p>Site Q and Site N</p> Signup and view all the answers

    Antimycin A binds to the site Q on Complex III, blocking electron flow from cytochrome b to cytochrome c1.

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

    What process do the actions of Complex III couple with?

    <p>Proton transport</p> Signup and view all the answers

    Match the following subunits/proteins with their respective characteristics:

    <p>Cytochrome b = Contains two hemes Rieske iron-sulfur protein = Contains 2Fe-2S centers Cytochrome c = Interacts with cytochrome c in the intermembrane space Ubiquinone = Shuttles electrons and protons across the membrane</p> Signup and view all the answers

    What is the primary role of glycerol 3-phosphate dehydrogenase in the respiratory chain?

    <p>Shuttling reducing equivalents from NADH to the mitochondrial matrix</p> Signup and view all the answers

    Ubiquinone is reduced to QH in the inner mitochondrial membrane by glycerol 3-phosphate dehydrogenase.

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

    What do the electron carriers cytochrome c and ubiquinone do in the context of supercomplexes?

    <p>They facilitate electron transfers and limit the production of reactive oxygen species.</p> Signup and view all the answers

    In β oxidation of fatty acyl–CoA, electrons are first transferred to the ___ of the dehydrogenase.

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

    Match the following components with their respective roles in the respiratory chain:

    <p>Cytochrome c = Facilitates electron transfer Ubiquinone = Electron carrier Acyl-CoA dehydrogenase = Catalyzes β oxidation Dihydroorotate dehydrogenase = Donates electrons to ubiquinone</p> Signup and view all the answers

    Which of the following statements is accurate regarding electron transfer pathways?

    <p>Multiple electron-transfer reactions can reduce ubiquinone.</p> Signup and view all the answers

    The reduced ubiquinone (QH) passes its electrons through Complex I.

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

    Name the two electron carriers mentioned in the respiratory chain that can diffuse between supercomplexes.

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

    What happens to the vesicles when F is depleted?

    <p>They cannot produce a proton gradient.</p> Signup and view all the answers

    Is ATP hydrolysis the same as ATP synthesis?

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

    What was the original name given to the isolated F that catalyzes ATP hydrolysis?

    <p>F ATPase</p> Signup and view all the answers

    The terminal __________ bond in ATP is cleaved and re-formed repeatedly on the enzyme surface.

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

    What does isotopic analysis of ATP synthesis reveal about the free-energy change?

    <p>It is close to zero.</p> Signup and view all the answers

    Match each component to its description:

    <p>F = Catalyzes ATP hydrolysis NADH = Electron donor in respiration ADP = Produces ATP when converted Pi = Inorganic phosphate involved in ATP synthesis</p> Signup and view all the answers

    Purified F can restore ATP synthesis capability to depleted vesicles.

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

    What does the presence of multiple 18O atoms in P released during ATP hydrolysis indicate?

    <p>The terminal pyrophosphate bond is cleaved and re-formed multiple times.</p> Signup and view all the answers

    Study Notes

    Oxidative Phosphorylation

    • Oxidative phosphorylation is the final stage of aerobic catabolism in organisms
    • It's the culmination of energy-yielding metabolic processes
    • All oxidative steps in the degradation of carbohydrates, fats, and amino acids converge at this stage of cellular respiration
    • The energy of oxidation drives the synthesis of ATP
    • This process accounts for most ATP synthesis in nonphotosynthetic organisms
    • In eukaryotes, it occurs in mitochondria, involving huge protein complexes embedded in the mitochondrial membranes
    • The pathway to ATP synthesis occurs within mitochondria

    Mitochondrial Respiratory Chain

    • The respiratory chain is a series of membrane-bound electron carriers
    • Electrons flow from electron donors (oxidizable substrates) to a final electron acceptor (usually oxygen)
    • This flow generates an electrochemical potential across the membrane, which is used to drive ATP synthesis
    • The chain consists of protein complexes, each performing specific electron-transfer reactions

    Principles of Oxidative Phosphorylation

    • Principle 1: Mitochondria play a central role in aerobic metabolism, acting as the site of the citric acid cycle, fatty acid β-oxidation, and amino acid oxidation pathways
    • Principle 2: Mitochondria trace their evolutionary origin to bacteria, evident in their structure and function
    • Principle 3: Electrons flow via a chain of membrane-bound carriers to the final electron acceptor, oxygen (O2)
    • Principle 4: Free energy from exergonic electron flow is used to transport protons across a membrane
    • Principle 5: Proton movement back through specific channels provides energy for ATP synthesis.

    Mitochondria: Components and Function

    • Outer membrane: readily permeable to small molecules and ions
    • Inner membrane: impermeable to most small molecules and ions, including protons (H+). Contains the crucial electron transfer chain components and ATP synthase
    • Cristae: foldings in the inner membrane, increasing surface area for electron transfer reactions
    • Matrix: fluid-filled space inside the inner membrane, containing enzymes of the citric acid cycle, fatty acid β-oxidation, and amino acid oxidation
    • Ribosomes: mitochondria's own ribosomes synthesize some proteins

    Electron Carriers in the Respiratory Chain

    • Ubiquinone (Coenzyme Q): hydrophobic quinone, readily diffuses within the membrane, accepting single or double electrons
    • Cytochromes: proteins with heme prosthetic groups; absorb visible light, and participate in one-electron transfers
    • Iron-sulfur proteins: proteins containing iron-sulfur clusters; readily accept or donate single electrons.

    Electron Carrier Complexes within the Respiratory Chain

    • Complex I (NADH dehydrogenase): Oxidizes NADH and transfers electrons to ubiquinone. Pumps protons across the inner mitochondrial membrane
    • Complex II (succinate dehydrogenase): Oxidizes succinate and transfers electrons to ubiquinone. Does not pump protons
    • Complex III (ubiquinone-cytochrome c oxidoreductase): Transfers electrons from ubiquinol (QH2) to cytochrome c. Pumps protons
    • Complex IV (cytochrome c oxidase): Transfers electrons from cytochrome c to oxygen (O2), reducing it to water (H2O). Pumps protons

    The Q Cycle

    • The Q cycle is how Complex III accepts electrons from ubiquinol, moving electrons to cytochrome c and pumping protons across the inner membrane
    • Two molecules of ubiquinol are sequentially oxidized, releasing 4 protons
    • This process is central to using the energy from electrons to create a proton gradient

    Complex IV (Cytochrome C Oxidase)

    • Complex IV is responsible for transferring electrons from cytochrome c to oxygen to produce water
    • It contains a binuclear center with copper atoms and a heme group, and this allows for efficient electron transfer and proton pumping
    • Involves the binding and reduction of oxygen to release water

    Regulation of Oxidative Phosphorylation

    • The rate of oxidative phosphorylation is typically controlled by the availability of ADP and oxygen.
    • Other conditions, such as the ADP/ATP ratio or intracellular concentrations, can also affect the rate of the process
    • The cell regulates oxidative phosphorylation to ensure ATP production matches the rate of ATP consumption

    Uncoupling Protein 1 (UCP1)

    • Brown adipose tissue (BAT) uses UCP-1 to uncouple mitochondrial respiration from ATP synthesis—producing heat instead of ATP from fuel oxidation

    Mitochondrial P-450 Monooxygenases

    • Involved in steroid hormone biosynthesis.
    • Located in the inner mitochondrial membrane.

    Mitochondrial DNA and Mutations

    • Mitochondria contain their own DNA (mtDNA) separate from nuclear DNA
    • mtDNA codes for some proteins needed for cellular respiration
    • Mutations in these are more pronounced with age due to the increased oxidative stress on the molecule
    • Mutations in mitochondrial genes may lead to several diseases, affecting different cell types varying in severity or severity of symptoms
    • Mitochondrial DNA mutations often affect the number and distribution of affected mitochondria, resulting in disease phenotypes that vary among individuals having the same mutation

    Apoptosis

    • Apoptosis, or programmed cell death, is a normal process that involves mitochondrial dysfunction
    • This dysfunction leads to an increase in the permeability of the outer mitochondrial membrane, which allows Cytochrome c to leave. This process triggers a cascade of events leading to cell death

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Chapter 19: Oxidative Phosphorylation PDF

    Description

    This quiz explores key concepts related to mitochondrial function and oxidative phosphorylation in aerobic organisms. It covers the evolutionary origins of mitochondria, their roles in energy production, and the significance of oxygen in the development of complex life forms. Test your understanding of these essential cellular processes.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser