Apoptosis and Cell Death Quiz
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Questions and Answers

What is the primary role of apoptosis in the human body?

  • To remove cells that have undergone necrosis.
  • To maintain a constant number of cells by removing unwanted or unneeded ones. (correct)
  • To initiate an immune response against damaged cells.
  • To increase cell division in response to injury.
  • Which of the following is a characteristic of apoptosis but not necrosis?

  • DNA fragmentation into 200 bp units. (correct)
  • Cell swelling and lysis.
  • Release of cellular contents and inflammation.
  • Uncontrolled cell death due to external factors.
  • During embryonic development, how does apoptosis contribute to the sculpting of digits?

  • It causes localized inflammation to separate the digits.
  • It promotes rapid cell growth between the digits.
  • It facilitates cell death in the interdigital tissue. (correct)
  • It triggers the fusion of cells to form the digits.
  • What happens to the outer surface of the plasma membrane during apoptosis?

    <p>It is coated with a different substance. (B)</p> Signup and view all the answers

    What is a key difference between how cells die through apoptosis versus necrosis?

    <p>Apoptosis is a programmed process, while necrosis is due to cellular injury. (A)</p> Signup and view all the answers

    What is the initial event in the cell death process described?

    <p>Condensation of the cell nucleus (D)</p> Signup and view all the answers

    Which cellular component is fragmented into membrane-bound apoptotic bodies during cell death?

    <p>The cytoplasm (B)</p> Signup and view all the answers

    What is the characteristic pattern of DNA fragmentation observed during apoptosis?

    <p>Fragmentation into a ladder of nucleosomes (C)</p> Signup and view all the answers

    What is the role of caspases in apoptosis?

    <p>To degrade other proteins (C)</p> Signup and view all the answers

    What is the direct effect of caspase activation on the nuclear membrane during apoptosis?

    <p>Irreversible breakdown of the nuclear membrane (C)</p> Signup and view all the answers

    What role does ATP play in programmed cell death?

    <p>It is required for apoptosis to occur. (B)</p> Signup and view all the answers

    During necrosis, which event directly leads to an inflammatory response?

    <p>Cell lysis and release of cellular contents (D)</p> Signup and view all the answers

    What is the immediate outcome of a cell undergoing apoptosis?

    <p>Phagocytosis by immune cells (B)</p> Signup and view all the answers

    Which of the following would be classified as a negative signal that could induce apoptosis?

    <p>Increased levels of oxidants (D)</p> Signup and view all the answers

    What is a key distinction between how apoptosis and necrosis affect tissues in vivo?

    <p>Apoptosis only affects individual cells, while necrosis affects areas of tissue (A)</p> Signup and view all the answers

    Which of these chemical reactions is associated with necrosis?

    <p>Production of prostaglandins (C)</p> Signup and view all the answers

    What is the correct order of apoptosis?

    <p>decision to activate, cell suicide, cell engulfment, and cell degradation (D)</p> Signup and view all the answers

    Which of the following cell death mechanisms is most closely associated with a potential therapeutic target in cancer treatment?

    <p>Apoptosis (B)</p> Signup and view all the answers

    In the context of ischemia/reperfusion injury, what is the temporal relationship between apoptosis in endothelial cells and myocyte cells?

    <p>Endothelial cell apoptosis precedes myocyte cell apoptosis. (B)</p> Signup and view all the answers

    What is a consequence of the evasion of apoptosis?

    <p>Development of cancer (B)</p> Signup and view all the answers

    Which type of genes are associated with the development of cancer, as indicated by the provided content?

    <p>Oncogenes, tumor suppressor genes, and DNA repair genes (C)</p> Signup and view all the answers

    In the context of the content, what is a possible cause of altered proteins during cell division?

    <p>Mutations in somatic and germline cells (C)</p> Signup and view all the answers

    What are caspases primarily responsible for?

    <p>Executing proteolytic cleavage during apoptosis (A)</p> Signup and view all the answers

    How are caspases typically activated within the cell?

    <p>Via proteolytic cleavage involving prodomain and linker region removal (A)</p> Signup and view all the answers

    What is the primary role of death domain-containing receptors in the extrinsic apoptotic pathway?

    <p>To induce proximity and activation of caspase-8 (D)</p> Signup and view all the answers

    Which pathway is primarily associated with mitochondrial involvement in apoptosis?

    <p>The intrinsic pathway only (B)</p> Signup and view all the answers

    What is the key function of cytochrome C in the intrinsic apoptotic pathway?

    <p>To activate APAF1 and form the apoptosome complex with casp9 (D)</p> Signup and view all the answers

    How does the protein Bid contribute to apoptosis?

    <p>By linking the extrinsic and intrinsic pathways through its interactions with the Bcl-2 family proteins (B)</p> Signup and view all the answers

    Which of the following experimental techniques specifically detects DNA fragmentation, a hallmark of apoptosis?

    <p>TUNEL staining (C)</p> Signup and view all the answers

    What is the role of IAPs (Inhibitor of Apoptosis Proteins) in the apoptotic pathways?

    <p>To inhibit the activity of caspases (C)</p> Signup and view all the answers

    What is the primary function of a proto-oncogene?

    <p>To become an oncogene when mutated. (D)</p> Signup and view all the answers

    If a cell has a mutated ras gene, what is the most likely result?

    <p>Continuous stimulation of cell proliferation. (B)</p> Signup and view all the answers

    What is the primary role of tumor suppressor genes?

    <p>To inhibit cell proliferation. (A)</p> Signup and view all the answers

    Which of the following tumor suppressor genes is associated with Wilm's tumor?

    <p>WT1 (A)</p> Signup and view all the answers

    What is the direct outcome of p53 activation?

    <p>Activation of the p21 protein and cell cycle arrest. (D)</p> Signup and view all the answers

    What can be inferred if the p53 gene is disrupted or deleted?

    <p>Uncorrected DNA damage, and hence uncontrolled cell proliferation. (D)</p> Signup and view all the answers

    What can cause a cell to undergo apoptosis?

    <p>Unrepairable DNA damage causing continuous cellular division (C)</p> Signup and view all the answers

    What would NOT be a common characteristic of apoptosis?

    <p>Cellular content leakage into the extracellular space (B)</p> Signup and view all the answers

    Flashcards

    Apoptosis

    A process of cell death that is programmed and controlled by the cell itself, leading to a neat and clean dismantling without causing inflammation or damaging neighboring cells.

    Necrosis

    A form of cell death that occurs due to external factors such as injury or toxins, resulting in uncontrolled cell breakdown and inflammation.

    Why is cell death important?

    The process of cell death plays a crucial role in maintaining a healthy population of cells by removing cells that are damaged, old, or no longer needed.

    Apoptosis in development

    Apoptosis is essential for development, eliminating unwanted cells during embryonic growth. For example, the tadpole's tail disappears through apoptosis.

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    Apoptosis in adults

    Apoptosis is a continuous process in adults, removing billions of healthy cells each hour. This ensures proper regulation and eliminates cells that fail quality control checks.

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    Nucleosome Ladder

    The process of breaking down DNA in the nucleus into fragments containing multiples of nucleosomes, creating a ladder-like pattern during apoptosis.

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    Procaspases

    These are inactive precursors to caspases, activated by specific signals triggering apoptosis.

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    Extrinsic Apoptosis Pathway

    A type of programmed cell death that is activated by external signals, often involving death receptor proteins on the cell surface.

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    Apoptotic Bodies

    Apoptotic bodies are formed during apoptosis as the cell's cytoplasm fragments, each enclosed within a membrane.

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    Caspases

    A class of enzymes involved in apoptosis, specifically targeting and breaking down proteins within the cell.

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    Programmed Cell Death (PCD)

    Programmed cell death (PCD) is a controlled process where a cell self-destructs to maintain tissue homeostasis.

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    ATP Dependence in Cell Death

    Apoptosis requires ATP, while necrosis occurs when ATP is depleted.

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    Inflammation in Cell Death

    Apoptosis involves phagocytosis of the cell by immune cells, preventing tissue inflammation. In contrast, necrosis results in cell lysis and inflammation.

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    Triggers of Apoptosis

    Apoptosis is triggered by either the withdrawal of positive signals (growth factors) or the receipt of negative signals (such as DNA damage or death activators).

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    Steps in Apoptosis

    Apoptotic pathways involve a series of steps, including the decision to activate the pathway, the actual cell death process, engulfment by phagocytes, and degradation of the remains.

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    Negative Signals in Apoptosis

    Examples of negative signals that trigger apoptosis include DNA damage by X-ray or UV light, chemotherapeutic drugs, misfolded proteins, and death activators like TNF-α and FasL.

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    Proto-oncogene

    A gene that promotes cell growth and division. When mutated, it becomes an oncogene and can contribute to cancer development.

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    Tumor suppressor gene

    A gene that normally prevents uncontrolled cell growth. When mutated, it loses its tumor suppressor function, leading to increased cancer risk.

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    DNA repair genes

    Genes involved in repairing damaged DNA. When mutated, they increase the likelihood of mutations accumulating in other genes, including proto-oncogenes and tumor suppressor genes, increasing cancer risk.

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    Evasion of apoptosis

    The escape from programmed cell death (apoptosis) by cancer cells, allowing them to survive and proliferate.

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    What is the molecular basis of cancer?

    Cancer can be considered a genetic disease resulting from mutations in genes involved in cell growth, division, and DNA repair.

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    What are caspases?

    Caspases are a family of proteases (enzymes that break down proteins) that play a crucial role in apoptosis, also known as programmed cell death.

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    How are caspases activated?

    Caspases are activated by proteolytic cleavage, where a specific part of the caspase molecule is removed, enabling it to become active.

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    Describe the extrinsic apoptotic pathway.

    The extrinsic pathway is triggered when a death receptor on the cell surface binds to its specific ligand, initiating a signaling cascade that leads to caspase activation.

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    Describe the intrinsic apoptotic pathway.

    The intrinsic pathway is activated by internal cellular stress, such as DNA damage or mitochondrial dysfunction, leading to the release of cytochrome c from mitochondria, ultimately activating caspases.

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    What are the ligands involved in ligand-induced cell death?

    FasL, TNF, and TRAIL are ligands that bind to their respective receptors on the cell surface, triggering the extrinsic apoptotic pathway.

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    What are the receptors involved in ligand-induced cell death?

    The Fas (CD95) receptor, TNF-R, and DR4 (TRAIL-R) are death receptors that bind to their specific ligands and initiate the extrinsic apoptotic pathway.

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    Explain the mechanism of ligand-induced cell death.

    When a ligand binds to its receptor, it triggers a series of events, including the assembly of death-inducing signaling complex (DISC) and activation of caspase-8, ultimately leading to apoptosis.

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    Describe the mitochondrial apoptotic pathway.

    The mitochondrial pathway is initiated by internal stress and involves the release of cytochrome c from mitochondria, forming a complex with Apaf-1 and caspase-9, ultimately activating other caspases and leading to apoptosis.

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    Oncogene

    A mutated version of a proto-oncogene that is constantly active, promoting excessive cell growth and contributing to cancer.

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    p53 gene

    The p53 gene is a crucial tumor suppressor gene responsible for halting the cell cycle when DNA damage occurs. It allows for DNA repair and, if unsuccessful, triggers programmed cell death (apoptosis).

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    Study Notes

    Cell Death & Apoptosis

    • Cell death is a crucial process for maintaining homeostasis in multicellular organisms
    • Two main forms of cell death: apoptosis and necrosis
    • Apoptosis is programmed cell death, crucial for development, tissue remodeling, and eliminating damaged/unwanted cells. Necrosis is an accidental form of cell death as a consequence of injury or stress
    • Apoptosis is a naturally regulated process to decrease the number of cells in the body
    • In apoptosis, cells shrink, condense their chromatin, and form apoptotic bodies that get engulfed by phagocytes
    • Necrosis involves cell swelling, damaging surrounding cells, and releasing inflammatory components
    • Apoptosis results in a clean cellular removal without harming neighbouring cells
    • Necroptosis is a programmed form of cell death and is a regulated form of necrosis that is activated by specific kinases to cause cell death

    Apoptosis

    • Apoptosis is signaled by various proteins, growth factors, and external stimuli
    • Examples of stimuli are increased oxidative stress, DNA damage, and withdrawal of growth factors
    • Cellular condensation is the initial step of apoptosis
    • Membranes are intact throughout apoptosis (preventing leakage of intracellular material)
    • ATP is required for apoptosis
    • The cell gets phagocytosed (engulfed by immune cells) without a major inflammatory response
    • DNA fragmentation occurs in apoptosis, creating a unique "ladder-like" pattern.
    • Individual cells appear affected in vivo (as opposed to whole tissues in necrosis)

    Morphological and Biochemical Changes in Apoptosis

    • Morphological changes during apoptosis include cell shrinkage, chromatin condensation, and membrane blebbing.
    • Biochemical changes include activation of caspases (proteases for apoptosis) and activation of endonucleases (which fragment DNA)

    Caspases

    • Caspases are proteases that are crucial in apoptosis
    • They are present as inactive precursors
    • Activated when signals for apoptosis are received
    • One caspase cleaves lamin proteins, leading to irreversible breakdown of the nuclear membrane

    Apoptosis Pathways

    • Two major pathways trigger apoptosis: intrinsic and extrinsic
    • Extrinsic pathway involves death receptors (initiated by external signals)
    • Intrinsic pathway occurs in response to cellular stress, e.g., DNA damage. This pathway involves the release of cytochrome c from mitochondria, initiating a cascade leading to caspase activation
    • The apoptosome is a multiprotein complex that activates caspases in apoptosis, usually from signalling in the intrinsic pathway.

    Cancer and Apoptosis

    • Cancer cells frequently demonstrate reduced apoptosis
    • Mutations in apoptosis-related genes can lead to uncontrolled cell growth and cancer development
    • Maintaining healthy levels of apoptosis is essential for preventing uncontrolled cell growth.

    Necrosis

    • Necrosis happens because of cell injury and irreversible cellular damage, potentially releasing reactive molecules into the tissues
    • Swelling of the cell is common in necrosis
    • Breakdown of the cell membrane is an important part of necrosis
    • Inflammation occurs upon necrosis
    • Loss of structural components occurs from leakage of cellular contents during necrosis

    Autophagic Cell Death

    • Autophagy is a cellular process in which the cell degrades part of its organelles
    • Autophagy can occur in healthy and stressed cells
    • A mechanism that can be either protective or destructive depending on the cell's internal state

    Other Forms of Cell Death

    • There are various forms of programmed cell death (PCD) beyond apoptosis (e.g. pyroptosis, autophagic cell death, ferroptosis, and immunogenic cell death)
    • Each form presents unique biochemical and morphological characteristics

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    Description

    Test your knowledge on the process of apoptosis and its significance in the human body. This quiz covers various characteristics of apoptosis, differences from necrosis, and its role in development. Explore concepts such as DNA fragmentation, caspase functions, and ATP's involvement in programmed cell death.

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