Mammalian cell biology 9

• what does cell motility do

  helps heal wounds, supports organ development
• prophase

  1. Chromosomes condense
  2. Nuclear envelope disrupts
  3. Spindle is formed
• metaphase

  1. Microtubules make contact with chromosomes
  2. Chromosomes are positioned in one plane
• anaphase

  1. Microtubules and motors pull on chromosomes
  2. Chromatids move to the poles
  3. Rapid elongation of the spindle
  4. Formation of a contractile ring
• telophase

  1. Cell middle contracts and separates (Cytokinesis)
  2. The chromosomes decondense
  3. The nuclear envelope is formed
• what is the mitotic spindle

  responsible for chromosome segregation
• G1 checkpoint

  is environment favourable 
• G2 checkpoint

  is all DNA replicated and is environment favourable 
• metaphase checkpoint

  ensures that all chromosomes are attached to the kinetochor microtubules
• normal situation at metaphase checkpoint

  all chromosomes align at the metaphase plate and sister chromatids are separated during anaphase
• Transient defects in microtubule-kinetochor attachment

  Progression into anaphase is delayed until the missing chromosome gets captured and aligned at the metaphase plate and
• what do molecular motors do in the spindle

  elongate the spindle, thereby supporting chromosome segregation in spindle function by:

  1. Sliding of polar microtubules against each other
  2. Pulling on astral microtubules
• process of cytokinesis

  • A contractile ring localises at the area of constriction
  • The ring forms near the cortex at the end of anaphase
  • The ring contains myosin, actin, regulators and actin-binding proteins
  • Myosin II and actin make the contractile ring
  • Blebbistatin disturbs the organisation actomyosin ring
  • Inhibition of myosin II abolishes cytokinesis
• essential functions of mitochondria

  ATP synthesis, fatty acid metabolism, control of programmed cell death/apoptosis
• who proposed the chemiosmotic theory

  Peter D. Mitchell in 1961
• process of oxidative phosphorylation

  1. Uptake of food molecules from the cytosol into the mitochondrial matrix
  2. Oxidation of Acetyl-CoA into carbon dioxide (Citric acid cycle = Krebs cycle); Production of the electron shuttle molecule NADH
  3. NADH transfers the electrons to the respiration chain at the inner membrane; electron flux is used to build up a proton gradient
  4. Back-flow of protons drives ATP synthesis
• what is apoptosis

  a mechanism by which cells die in a controlled way, followed by recycling of their building blocks
• what organisms have apoptosis

  multi cellular
• what advantages does apoptosis have

  separation of fingers and toes in a developing human embryo
• who proposed apoptosis theory

  Carl Vogt (1817-1895) German Zoologist
• what induces apoptosis

  • Electrons can "leak" out of the mitochondrial respiration chain
  • reactive oxygen species (ROS)
  • ROS is highly damaging and induces apoptosis
• process of apoptosis

  1. Stress (e.g. cell damage) triggers "apoptotic signalling"
  2. apoptotic proteins cause damage to the mitochondria, which releases factors that activate apoptotic enzymes
  3. Nucleus condenses
  4. Cell starts "blebbing"
  5. Nucleus and DNA fragmentises
  6. Phagocytosis of "apoptotic bodies" by a phagocytes