The Nucleus and Cell Death

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medstudent2017
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312128
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The Nucleus and Cell Death
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2015-11-26 08:05:52
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The Nucleus and Cell Death
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  1. What is one of the only cells in the body that lacks a Nucleus
    Erythrocytes (Red blood cells)
  2. Define Chromatin
    A complex of DNA, proteins, histones, and non-histone proteins in the nucleus of a eukaryotic cell
  3. Define Chromosome
    Structure composed of a long DNA strand and associated proteins. It contains part if not all of the heredity info
  4. Define a Nucleosome
    A basic unit of DNA packing
  5. What are the three types of RNA in the nucleus transcribed from DNA. Desribe their functions.
    • rRNA, Used to make new ribosomes
    • mRNA, codes for proteins
    • tRNA, each represents an amino acid, used during translation to make polypeptide chains out of mRNA
  6. All of the RNA are synthesized where and are exported where
    Synthesized in the nucleus and exported to the cytoplasm
  7. Heterochromatin is
    Highly condensed transcriptionally inactive chromatin (looks dark in the cell)
  8. Where is chromatin often found in the cell
    Attached to the nuclear lamina on the inner membrane of the nucleus
  9. Nuclear lamina
    • Provides mechanical support for the nuclear membrane and controls the disassembly of the nuclear envelope in mitosis
    • It is composed of intermediate filaments
  10. Euchromatin is
    Much less condensed transcriptionally active chromatin (only mRNA and tRNA are transcribed from genes in these)
  11. Where are the new ribosomes made
    The nucleolus, it also contains the genes that synthesize rRNA's
  12. What makes the nucleolus appear so dark
    It contains so many nascent ribosomes in the process of assembly
  13. Ribosomes are composed of proteins that surround what
    A core of rRNA
  14. The rRNA is transcribed where
    Nucleolus
  15. What information do the Y chromosome contain
    Only information necessary for men. Testosterone, sperm development ect.
  16. What is a kinetochore
    This is what links chromosomes to microtubules at the centromere during mitosis
  17. What three DNA sequences are required to produce a eukaryotic chromosome that can be replicated
    • Telomere
    • Replication Origin
    • Centromere
  18. Human peripheral lymphocyte
    This is when two copies of chromosomes occupy distinct locations in a nucleus
  19. The NPC is
    Nuclear Pore Complex, it is on the nucleus and is responsible for the movement of all macromolecules
  20. Signal for Nuclear Import
    • Nuclear Localization Signal (NLS)
    • Usually contains basic amino acids
  21. Signal for Nuclear Export
    • Nuclear Export Signal (NES)
    • Usually contains hydrophobic amino acids
  22. How is the unique amino acid sequence for protein delivery formed
    After the protein is formed it folds with the signal on a tail, or at a crevice in the protein made of different segments of the protein folded to align them for recognition
  23. How does a protein end up in the right place after being made
    It contains a unique amino acid sequence recognized by a carrier that binds it and takes it to its destination and releases it
  24. What happens to the protein carrier after delivering the protein
    It recycles back to the cytoplasm
  25. What are the nuclear carriers that recognize NLS and NES
    • Importins
    • Exportins
  26. Ran (ras-related nuclear protein) is
    A small GTPase that regulates cargo binding and releasing for both importins and exportins
  27. Inhibition of splicing of the rRNA in the nucleolus would have what effect on its destination
    If splicing doesn't happen exportation won't happen
  28. The exportation of rRNA is has a very tight relationship with
    The splicing and processing of newly transcribed mRNA and its export
  29. Senescence is
    The process of aging
  30. What are te primary differences in apoptosis and necrosis
    • Necrosis is unplanned death, and the cell in a way implodes.
    • Apoptosis is planned death and phagocytes consume the cell in efforts protecting cells surrounding it from its potentially harmful interior.
  31. In what conditions is apoptosis advantageous
    • To delete unwanted features
    • For the sculpting of tissues (webbing)
    • To control the number of cells in the body
    • For eliminating unwanted cells
  32. Why is apoptosis important for homeostasis
    Homeostasis is a balance between cell proliferation and cell death
  33. Why would apoptosis be researched so heavily
    If you can initiate planned death in infected cells you could cure a lot of diseases
  34. The severity of a noxious stimulant can effect cell death how
    If it is too severe it will cause the cell to undergo necrosis, if severity is mild and the cell can't repair the damage done it will under go apoptosis
  35. What is the BCL2 family
    A family of pro and anti apoptosis triggering proteins
  36. What is a caspase
    This is the protein that apoptosis always ends with, they are cystein proteases and cleave proteins at the C terminal
  37. How many caspases does it take to initiate cell death
    Just one molecule, every cell contains inactive ones
  38. What are the most important targets of caspases
    • Nuclear lamina
    • Cytoskeleton
    • Destruction of these is what causes blebbing
  39. What is a key feature of apoptosis not seen in necrosis
    The dying cell is engulfed by a phagocytic cell in apoptosis and no leakage of cellular contents therefore no inflammation response
  40. What are the physical manifestations of a cell undergoing necrosis
    • The cell swells
    • The cell bursts (Bleb)
    • An inflammation response follows
  41. What are two other markers that will lead to cell death
    Cytochrome C, and Phosphotidylserine being presented on the outside of a cell
  42. What are the two different activation pathways for apoptosis
    Extrinsic and Intrinsic
  43. In general intrinsic apoptosis is initiated via the involvement of what organelle through what action
    Mitochondria by the release of cytochrome C
  44. What signal on the outer leaflet of the cell membrane recruits phagocytes for apoptosis and how does it happen
    Phosphatidylserine (normally only in the inner leaflet) it is flipped there by scramblase which is different then the one found active on the ER membrane
  45. Cytochrome C assembles with and activates caspase to form what
    Apoptosome
  46. What do telomeres do and where are they located
    Telomeres cap the ends of chromosomes so they can’t be degraded
  47. Knobs on chromosomes 13, 14, 15, 21, and 22 indicate
    The positions of genes that code for rRNA
  48. All movement of macromolecules between the nucleus and cytoplasm occurs through
    NPCs
  49. Completely folded proteins as well as large complexes can fit through the
    NPC's (unlike protein import into the ER and mitochondria in which only unfolded proteins are small enough to cross the membrane).

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