Biomedical Sciences I: Mitochondrion Quiz
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Questions and Answers

Which complex does FADH2 enter the electron transport chain?

  • Complex III
  • Complex II (correct)
  • Complex I
  • Complex IV

    • What is produced as a result of electron transfer to O2 in the electron transport chain?

  • Ubiquinone
  • H2O (correct)
  • NADH
  • ATP

    • How many molecules of ATP can be generated from a single molecule of glucose?

  • 36 (correct)
  • 18
  • 30
  • 42

    • What triggers the activation of caspases during apoptosis?

    <p>Cleavage of specific aspartic acids</p> Signup and view all the answers

    What type of proteins do mitochondrially encoded genes typically influence?

    <p>Mitochondrial proteins</p> Signup and view all the answers

    What successfully builds an electrochemical gradient in aerobic metabolism?

    <p>Protons (H+)</p> Signup and view all the answers

    The spherical F1 head of ATP synthase is primarily involved in which reaction?

    <p>Phosphorylation of ADP to ATP</p> Signup and view all the answers

    What characterizes mitochondrial myopathies?

    <p>Neuromuscular symptoms</p> Signup and view all the answers

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

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

    Which pathway is NOT one of the two best-understood activation mechanisms for caspases?

    <p>Autophagic pathway</p> Signup and view all the answers

    What role does the TOM complex play in mitochondrial function?

    <p>Import of nearly all nucleus-encoded mitochondrial proteins</p> Signup and view all the answers

    Which complex is responsible for the insertion and folding of b-barrel proteins?

    <p>SAM complex</p> Signup and view all the answers

    How do mitochondrial precursors remain in an unfolded state in the cytosol?

    <p>Thanks to chaperones of the hsp70 family</p> Signup and view all the answers

    What is the function of the OXA complex in mitochondria?

    <p>Mediates the insertion of mitochondrial genome-encoded membrane proteins</p> Signup and view all the answers

    What initiates mitochondrial fission?

    <p>Intervention of the endoplasmic reticulum</p> Signup and view all the answers

    What are mitochondria capable of doing as dynamic organelles?

    <p>Fusing with each other and splitting</p> Signup and view all the answers

    What does the interaction of mitochondria with the microtubular cytoskeleton determine?

    <p>Their orientation and distribution within the cell</p> Signup and view all the answers

    What color results from a fusion of a green-fluorescent mitochondrion with a red-fluorescent one?

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

    What is NOT a component of mitochondrial protein transport?

    <p>Golgi apparatus</p> Signup and view all the answers

    What is a function of the TIM complexes in mitochondria?

    <p>Transport of proteins at the inner membrane</p> Signup and view all the answers

    What characteristic of mitochondria allows them to change shape and move within cells?

    <p>Association with the cytoskeleton</p> Signup and view all the answers

    Which feature is NOT part of the mitochondrial structure?

    <p>Chlorophyll-rich matrix</p> Signup and view all the answers

    Which component of mitochondria is responsible for most ATP production?

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

    What role does mitochondrial DNA (mtDNA) play in cellular functions?

    <p>Storing genetic information for protein synthesis</p> Signup and view all the answers

    How is mitochondrial DNA inherited in humans?

    <p>Uniparentally from the mother</p> Signup and view all the answers

    What is a biological consequence of the high mutation rate of mtDNA?

    <p>Heteroplasmy in offspring</p> Signup and view all the answers

    What is a primary function of the intermembrane space in mitochondria?

    <p>Initiating cell death mechanisms</p> Signup and view all the answers

    Why are sperm mitochondria eliminated from fertilized eggs?

    <p>To ensure maternal inheritance of mtDNA</p> Signup and view all the answers

    What process occurs when nonfunctional mitochondria undergo organized degradation?

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

    Which of the following best describes the matrix of the mitochondrion?

    <p>Gel-like consistency filled with enzymes</p> Signup and view all the answers

    What is the primary reason for the degradation of mitochondrial DNA in sperm cells?

    <p>To allow maternal dominance of mtDNA</p> Signup and view all the answers

    What occurs to the mitochondrial protein import when there is a loss of the electrochemical gradient?

    <p>It becomes inefficient.</p> Signup and view all the answers

    What is produced when pyruvate is decarboxylated and linked to coenzyme A in the mitochondria?

    <p>Acetyl CoA</p> Signup and view all the answers

    Which organelle regulates the calcium concentration of the cytosol?

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

    Which steps in aerobic metabolism are directly associated with the generation of NADH?

    <p>Glycolysis and the TCA cycle</p> Signup and view all the answers

    What is the role of PINK1 in the context of mitochondria?

    <p>Phosphorylates ubiquitin and Parkin</p> Signup and view all the answers

    How does NADH produced during glycolysis enter the mitochondrion?

    <p>By the malate-aspartate shuttle</p> Signup and view all the answers

    Which component of the electron transport chain is a soluble protein in the intermembrane space?

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

    What is the main outcome of the electron transport chain in mitochondria?

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

    What is shared between the mitochondrion and the cytoplasm in the context of heme group biosynthesis?

    <p>Biosynthesis process</p> Signup and view all the answers

    Study Notes

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    Biomedical Sciences I: Cellular Biology I

    • Course information: Biomedical Sciences I, Cellular Biology I
    • Instructor: Lorena Di Pietro
    • Email: [email protected]

    Mitochondrion and Aerobic Respiration

    • Title: Mitochondrion and Aerobic Respiration.

    Mitochondrion

    • Mitochondria are dynamic structures.
    • They move within cells, constantly changing shape, dividing, and fusing.
    • They are associated with the cytoskeleton, which influences their distribution.
    • Morphology varies depending on cell type, (e.g., individual bean-shaped organelles, highly branched, interconnected tubular networks).
    • Dimensions: 1–4 µm in length.

    Mitochondrion: Endosymbiosis (page 6)

    • Mitochondria evolved from an ancient aerobic bacterium via endosymbiosis.
    • Ancestral eukaryote consumed aerobic bacteria that then became mitochondria.
    • A second endosymbiotic event led to photosynthesis bacteria becoming chloroplasts in the early eukaryote.

    Mitochondrion: Organization and Structure (page 7)

    • Double-membrane system (inner and outer membranes + cristae).
    • Intermembrane space
    • Matrix

    Mitochondrion: Outer Mitochondrial Membrane (page 8)

    • Smooth and uniform outer membrane, similar to the outer bacterial membrane.
    • Freely permeable to small ions and molecules (<50kDa) due to nonselective porins.
    • Contains enzymes with varied functions (e.g., oxidation of epinephrine, degradation of tryptophan, elongation of fatty acids).
    • Composed of 50% lipids.

    Mitochondrion: Inner Mitochondrial Membrane (page 9)

    • Enriched in proteins (>100 different proteins, ~80%).
    • Highly impermeable.
    • Contains two domains:
      • Inner boundary membrane, parallel to the outer membrane, with protein import translocases lacking cholesterol but rich in cardiolipin.
      • Cristae, invaginated membranous sheets with 25% lipids containing enzymes and structural proteins for aerobic respiration and ATP production.
      • Cristae junctions connect inner and outer domains.

    Mitochondrion: Intermembrane Space (page 10)

    • Contains proteins involved in cell death initiation.
    • pH and ionic composition similar to cytoplasm.

    Mitochondrion: Matrix (page 10)

    • Gel-like consistency with high concentration of soluble proteins (e.g., Krebs cycle enzymes)
    • Contains mitochondrial DNA (~1% of total cellular DNA content).
    • Contains free ribosomes which are smaller than cytoplasmic ribosomes.

    Mitochondrion: mtDNA (page 11)

    • mtDNA encodes 13 mitochondrial polypeptides, 2 rRNA, and 22 tRNA.
    • mtDNA has a high mutation rate, leading to heteroplasmy.
    • Lower fidelity of mitochondrial DNA replication, and inefficent DNA repair.
    • Useful in estimating dates of recent evolutionary events.

    Mitochondrion: Inheritance (page 12, 13)

    • Mitochondrial inheritance is uniparental (maternal) in both animals and plants.
    • Typical human oocytes contain ~100,000 copies of mtDNA.
    • Sperm mtDNA is degraded during maturation.
    • Sperm mitochondria are eliminated from the fertilized egg cell by autophagy.
    • Germ-line mitochondrial mutations are passed to the next generation by the mother.

    Mitochondrion: Biparental Inheritance (page 14)

    • While maternal inheritance of mtDNA is the norm, very rare instances of biparental mtDNA transmission have been observed in specific families.
    • These cases could potentially disrupt the idea of strict maternal mitochondrial heritage.

    Mitochondrion: Mitochondrial Protein Import (pages 15-17)

    • Mitochondrial proteins are synthesized on cytosolic ribosomes and imported by targeting signals.
    • Key translocator complexes: TOM (outer membrane), SAM (outer membrane), TIM (inner membrane) mediate the process.
    • OXA complex facilitates membrane protein insertion.
    • Chaperone interaction (e.g., hsp70 family) helps in precursor protein processing and insertion.

    Mitochondrion: Dynamic Organelles (page 18)

    • Mitochondria can fuse (or merge) and/or split.
    • Typically associated with the microtubular cytoskeleton.
    • Endoplasmic reticulum participates in mitochondrial division, starting the process

    Mitochondrion: Video - Mitochondrial Dynamics (page 19)

    • Video demonstrates mitochondria labeled with fluorescent proteins fusing and/or dividing.

    Mitochondrion: Mitochondrial Degradation (pages 20-21)

    • Nonfunctional mitochondria undergo organized degradation (mitophagy).

    • Inefficient protein import is linked to the loss of electrochemical gradient, and accumulation of PINK1 (a protein kinase) on the outer membrane.

    • PINK1 phosphorylates ubiquitin and regulator Parkin which initiates autophagosome formation.

    • Mutations in PINK1 and Parkin are linked to Parkinson's disease related to dysfunctional mitochondria accumulation.

    Mitochondrion (page 22):

    • Role in respiration and the urea cycle.
    • Involvement in lipid biosynthesis and apoptosis.
    • Regulates cytosolic Ca2+ concentration

    Aerobic Metabolism

    • Glycolysis: Glucose metabolism to pyruvate is initiated outside the mitochondria, and converts glucose into chemical energy.

    • Pyruvate and/or Fermentation: Oxygen availability is key; with oxygen (aerobic), pyruvate enters mitochondria; without oxygen (anaerobic), fermentation begins.

      • Decarboxylation: Pyruvate is converted into Acetyl CoA with the release of CO2 and creation of NADH from NAD+.

    • TCA Cycle (Citric Acid Cycle): Acetyl CoA proceeds through the TCA cycle in the mitochondrion, producing NADH and FADH2.

    • **Electron Transport Chain (ETC): ** High-energy electrons from NADH and FADH2 are transferred along the ETC, generating a proton gradient.

    Electron Transport Chain (pages 28-31)

    • 4 complexes and ubiquinone and cytochrome c support electron transfer.
    • Ubiquinone acts as an electron carrier.
    • Cytochrome c is a peripheral protein.
    • The ETC passes electrons to molecular oxygen forming water, releasing energy that is utilized for ATP synthesis.
    • The process conserves free energy through proton translocation across the inner membrane.

    Aerobic Metabolism: ATP Synthesis (pages 32-33)

    • The electrochemical proton gradient drives ATP synthase.
    • ATP synthase is a protein complex comprising F1 (spherical head) and F0 (basal portion), embedded in the membrane.
    • Proton flow through ATP synthase facilitates ADP to ATP phosphorylation.
    • Approx. 36 ATP molecules are generated from one glucose molecule.

    Mitochondrial Apoptosis (page 34)

    • Caspases are proteases, activated only during apoptosis.
    • Two main activation pathways, extrinsic and intrinsic.

    Mitochondrial Diseases (page 35)

    • Heterogeneous group of disorders caused by mtDNA or nuclear gene mutations.
    • Often associated with neuromuscular symptoms (Mitochondrial Myopathies).
    • Maternal inheritance often but not always the case.

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    Description

    Test your knowledge on mitochondria and their role in aerobic respiration as part of the Biomedical Sciences I course. This quiz covers dynamic structures of mitochondria, their morphology, and connection to cellular processes. Perfect for students looking to reinforce their understanding in Cellular Biology I.

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