Apoptosis

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  • Created by: Steff06
  • Created on: 24-04-16 14:20
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  • Apoptosis
    • PROGRAMMED CELL DEATH. Occurs in MULTICELLULAR organisms.
    • Cell NECROSIS = Untidy and damaging cell death that occurs after trauma and releases hydrolytic enzymes.
    • Events:
      • 1. ENZYMES break down the cell CYTOPLASM.
      • 2. Cytoplasm becomes DENSE, with organelles tightly packed.
      • 3. Cell surface MEMBRANE CHANGES and small bits called BLEBS form.
      • 4. CHROMATIN CONDENSES and nuclear envelope BREAKS. DNA breaks into FRAGMENTS
      • 5. Cell breaks into VESICLES that are taken up by PHAGOCYTOSIS. Cellular debris is disposed of and does not damage any other cells or tissues.
    • Apoptosis process occurs very quickly.
    • Controlled by cell SIGNALS including CYTOKINES, HORMONES, GROWTH FACTORS, NITRIC OXIDE.
      • Nitric oxide can induce apoptosis by making the INNER MITOCHONDRIAL membrane more PERMEABLE to hydrogen ions and dissipating the proton gradient.
    • Part of PLANT and ANIMAL tissue development.Excess cells shrink, fragment and are phagocytosed so components are reused and no harmful hydrolytic enzymes are released.
    • Tightly regulated during development, different tissues use DIFFERENT signals for inducing it.
    • PROTEINS released into cytosol + BIND to apoptosis inhibitor proteins and allow the process to take place.
    • In limb development, apoptosis causes digits to SEPARATE from eachother.
    • Rate of cells dying should BALANCE rate of cells produced by mitosis.
      • If not balanced: Too little apoptosis leads to formation of TUMOURS. Too much leads to cell LOSS and DEGENERATION.

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