week 1

• 4 common features of all cells are structure, function, reproduction, and the cell cycle
• The purposes of cell division are organism growth and development, damage repair of tissues, and reproduction to produce more cells
• mitosis is the division of the nuclei
• cytokinesis is the division of the cytoplasm
• unlike animal cells which have cell membranes, plant cells possess cell walls
• cells that frequently divide include skin cells, intestinal cells, and cheek cells
• a type of cell that infrequently divides are liver cells
• a type of cell that never divides are nerve cells
• If the cell cycle is not regulated, it could potentially lead to the development of cancer cells
• The stages of the cell cycle are: G1, S, G2, and M.
• G1 phase is the growth phase of the cell cycle where the cell grows and prepares for DNA replication.
• S is the stage of the cell cycle where the DNA replication occurs.
• G2 is where the cell rapidly grows to prepare for cell division
• The M-phase is mitosis.
• Interphase is composed of the G1, S, and G2 phase.
• Gap phases: preparation of the cell for mitosis
• Label this

  A) interphase

  B) g1

  C) s

  D) g2

  E) m

  
• Checkpoints during the cell cycle occur at the G1 phase (where it can go to the G0 phase), G2 phase (where the MPF complex occurs), and the m-phase (where the cells are stopped from dividing during mitosis).
• Mitosis-promoting factors or MPFs are at maximum levels during mitosis and the levels are correlated with cyclin levels.
• cyclin is a regulatory protein which activates kinase via phosphorylation. When cyclin is added to CDK forms MPF.
• The platelet derived growth factor (PDGF) is a growth factor that stimulates the cell division to result in the production of tissue to repair damage. The fibroblasts have a receptor to bind tyrosine kinases present in PDGF.
• Prophase = chromosomes appear with sister chromatids. The spindle apparatus forms (contains microtubules).
• Prometaphase = nuclear envelope breaks down. The microtubules attach to chromosomes at the centromere (kinetochores)
• Metaphase = sister chromatids migrate to the middle of the cell. Spindle apparatus is complete. Chromosomes line up.
• Anaphase = chromatids (chromosomes) are pulled along by kinetochore microtubules
• Telophase = spindle apparatus breaks down. Nuclear envelope forms around chromosomes. Chromosomes de-condense.
• Cytokinesis = division of cytoplasm and formation of cell membrane around two new cells
• Stem cells can differentiate into different cells and are normally derived from embryonic tissues, umbilical cord, or amniotic fluid.
• Struggles when differentiating stem cells into other cell types include: the cells being rejected by the immune system, or the stem cells growing irregularly or differentiating into undesired cell types