BMS 324: Molecular Genetics and Cell Regulation - Cell Death
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Questions and Answers

What is the primary function of cell death in maintaining tissue size?

  • To destroy cells that are no longer needed (correct)
  • To maintain a balance between cell growth and division
  • To produce cells at the same rate as they are destroyed
  • To regulate the rate of cell migration
  • What is the characteristic feature of cells undergoing apoptosis?

  • They shrink and condense (correct)
  • They swell and burst
  • They migrate to other tissues
  • They undergo rapid cell division
  • What is the role of macrophages in apoptosis?

  • To produce inflammatory responses
  • To engulf and digest apoptotic cells (correct)
  • To stimulate cell growth and division
  • To regulate cell migration
  • What is the primary difference between apoptosis and necrosis?

    <p>Apoptosis is a programmed process, while necrosis is random</p> Signup and view all the answers

    During embryonic development, what is the role of apoptosis in shaping hands and feet?

    <p>To eliminate unwanted cells and sculpt structures</p> Signup and view all the answers

    What is the consequence of necrotic cell death?

    <p>Spilling of cellular contents, leading to inflammation</p> Signup and view all the answers

    What is the role of apoptosis as a quality-control process in development?

    <p>To eliminate abnormal, misplaced, or nonfunctional cells</p> Signup and view all the answers

    What is the likely cause of necrosis?

    <p>Energy depletion, leading to metabolic defects</p> Signup and view all the answers

    What is the result of apoptotic cells detaching from their neighbors?

    <p>They round up and detach from their neighbors</p> Signup and view all the answers

    What is the characteristic of the caspase cascade?

    <p>It is destructive and self-amplifying but also irreversible</p> Signup and view all the answers

    What is the function of the death domain in death receptors?

    <p>It is required for the receptors to activate the apoptotic program</p> Signup and view all the answers

    What is the role of Fas ligand in the extrinsic pathway of apoptosis?

    <p>It activates the Fas death receptors on the surface of target cells</p> Signup and view all the answers

    What is the main function of the DISC complex?

    <p>It forms a complex with initiator caspases to induce apoptosis</p> Signup and view all the answers

    What is the role of FLIP in the extrinsic pathway of apoptosis?

    <p>It inhibits the activation of the extrinsic pathway</p> Signup and view all the answers

    What is the function of the intrinsic pathway of apoptosis?

    <p>It is activated by stresses such as DNA damage from inside the cell</p> Signup and view all the answers

    What is required for the intrinsic pathway of apoptosis to operate?

    <p>At least one of Bax and Bak proteins</p> Signup and view all the answers

    What is the result of the activation of the caspase cascade in the extrinsic pathway of apoptosis?

    <p>It induces apoptosis by cleaving and activating downstream executioner caspases</p> Signup and view all the answers

    What is the role of BH3-only proteins in the intrinsic pathway of apoptosis?

    <p>They mediate the inhibition of anti-apoptotic Bcl2 family proteins</p> Signup and view all the answers

    What is the function of anti-apoptotic Bcl2 family proteins?

    <p>They bind to and inhibit pro-apoptotic Bcl2 family proteins</p> Signup and view all the answers

    How do IAPs help control caspases?

    <p>They bind to and inhibit activated caspases</p> Signup and view all the answers

    What is the role of BIR domains in IAPs?

    <p>They enable IAPs to bind to and inhibit activated caspases</p> Signup and view all the answers

    Why do insect viruses encode IAP proteins?

    <p>To prevent a host cell that is infected by the virus from killing itself by apoptosis</p> Signup and view all the answers

    What happens to caspases when they are polyubiquitylated by IAPs?

    <p>They are marked for destruction by proteasomes</p> Signup and view all the answers

    What is the outcome of activating a caspase cascade?

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

    What is the role of IAPs in regulating apoptosis?

    <p>To set an inhibitory threshold that caspases must overcome to trigger apoptosis</p> Signup and view all the answers

    What is the outcome of deleting the genes that encode IAPs in flies?

    <p>Apoptosis is blocked in flies</p> Signup and view all the answers

    What is the effect of inactivating one of the two genes that encode IAPs in flies?

    <p>All cells in the developing fly embryo undergo apoptosis</p> Signup and view all the answers

    What is the role of survival factors in regulating apoptosis?

    <p>They bind to cell-surface receptors and activate intracellular signaling pathways that suppress the apoptotic program</p> Signup and view all the answers

    Why do nerve cells that receive enough survival signals live?

    <p>Because they suppress the apoptotic program</p> Signup and view all the answers

    What is the role of Bcl2 family proteins in regulating apoptosis?

    <p>They regulate the apoptotic program</p> Signup and view all the answers

    How do some survival factors act in Drosophila?

    <p>By phosphorylating and inactivating anti-IAP proteins</p> Signup and view all the answers

    What is the outcome of deleting the genes that encode XIAP or Smac/Diablo and Omi in mice?

    <p>The mice develop normally</p> Signup and view all the answers

    What is the process by which phagocytic cells engulf and remove apoptotic cells?

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

    What is the main change that occurs on the surface of an apoptotic cell that recruits phagocytic cells?

    <p>Flip of phosphatidylserine from the inner to the outer leaflet</p> Signup and view all the answers

    What is the consequence of excessive apoptosis in certain diseases?

    <p>Tissue damage</p> Signup and view all the answers

    What is the function of the Fas death receptor and Fas ligand genes?

    <p>To stimulate apoptosis</p> Signup and view all the answers

    What is the role of the tumor suppressor protein p53 in cancer development?

    <p>To promote apoptosis</p> Signup and view all the answers

    What is the effect of p53 dysfunction on cancer cells' response to anticancer drugs?

    <p>Decreased sensitivity</p> Signup and view all the answers

    What is the consequence of decreased apoptosis in cancer development?

    <p>Cancer development</p> Signup and view all the answers

    What is the percentage of human cancers in which the p53 gene is mutated?

    <p>50%</p> Signup and view all the answers

    Study Notes

    Cell Death and Apoptosis

    • The growth, development, and maintenance of multicellular organisms depend on the production of cells and mechanisms to destroy them.
    • Cell death is not a random process but occurs by a programmed sequence of molecular events.
    • Apoptosis (programmed cell death) is a process by which cells die and are engulfed by other cells, including macrophages.

    Characteristics of Apoptosis

    • Cells dying by apoptosis undergo characteristic morphological changes: • Shrinkage and condensation • Cytoskeleton collapse • Nuclear envelope disassembly • Nuclear chromatin condensation and fragmentation • Cell surface breakdown into membrane-enclosed fragments (apoptotic bodies)

    Contrasting Apoptosis with Necrosis

    • Apoptosis is distinct from necrosis, a process of cell death caused by acute insults (trauma, lack of blood supply) leading to: • Cell swelling and bursting • Inflammatory response • Energy depletion and metabolic defects • Loss of ionic gradients across the cell membrane

    Functional Roles of Apoptosis

    • Apoptosis helps sculpt body shape during embryonic development
    • Apoptosis eliminates unwanted cells, including: • Abnormal, misplaced, nonfunctional, or potentially dangerous cells • Cells that form structures that are no longer needed (e.g., tadpole tail)
    • Apoptosis functions as a quality-control process during development

    Regulation of Apoptosis

    • The caspase cascade is a self-amplifying and irreversible process
    • Two primary activation mechanisms in mammalian cells: • Extrinsic pathway (death receptors, Fas ligand, and Fas death receptor) • Intrinsic pathway (mitochondrial pathway, Bax, Bak, and anti-apoptotic Bcl2 family proteins)

    Intrinsic Pathway of Apoptosis

    • Cells can activate apoptosis in response to stresses, such as DNA damage
    • At least one of the Bax and Bak proteins is required for the intrinsic pathway
    • Anti-apoptotic Bcl2 family proteins (Bcl2 and BclXL) inhibit apoptosis by binding to and inhibiting pro-apoptotic Bcl2 family proteins

    Inhibitors of Apoptosis (IAPs) and Anti-IAPs

    • IAPs bind to and inhibit activated caspases
    • Some IAPs polyubiquitylate caspases, marking them for destruction by proteasomes
    • Balance between IAPs and anti-IAPs is crucial for controlling apoptosis

    Extracellular Survival Factors and Apoptosis

    • Most animal cells require continuous signaling from other cells to avoid apoptosis
    • Survival factors bind to cell-surface receptors, activating intracellular signaling pathways that suppress apoptosis
    • Some survival factors stimulate the synthesis of anti-apoptotic Bcl2 family proteins or inhibit pro-apoptotic BH3-only proteins

    Phagocytic Removal of Apoptotic Cells

    • Apoptotic cells and their fragments are efficiently eaten by phagocytic cells
    • Chemical changes on the surface of apoptotic cells, including the exposure of phosphatidylserine, recruit phagocytic cells

    Apoptosis and Disease

    • Excessive or insufficient apoptosis can contribute to various diseases
    • Examples include autoimmune disease, cancer, and neurodegenerative disorders

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    Description

    This quiz covers the molecular events of cell death, a programmed sequence necessary for maintaining tissue size in multicellular organisms. Learn about the mechanisms that regulate cell death, an essential process for growth and development.

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