Mitosis-cell division; Interphase-most of the time the cell is in this cycle
What is interphase ?
The period that covers all the time the cell is not undergoing mitosis
What is Mitosis?
The orderly events that involve the division of the nucleus
What are the diff. phases of the cell cycle?
G0, G1, G2, S
G1 Phase (pre)
Variable in length (1 yr, hrs, days); Protein Synthesis; Regains normal size-Cell Growth; Checkpt. prior to entry to S phase (is enviro. favorable for division? is DNA intact?)
S Phase
DNA is replicated; 6-8 hrs. in length; Semiconservative Replication (old & new strands)
G2 Phase (post)
Completes preparation for cell division; 3-6 hours in length; Synthesis of tubulin for microtubules; Checkpt. for repair of DNA (has DNA totally replicated?)
M Phase
Mitosis; 1-2 hours in length
G0
Entered from G1; Cell is not dividing but still active b/c there's sufficient supply of that type of cell; Cardiac muscle and neurons permanently in G1
The cell cycle is regulated by what?
External and Internal factors
External Regulation
Specific receptors on the cell surface send cytoplasmic signals to cellular components to divide
Internal Regulation
Regulated by Cyclins & Maturation promoting factor (MPF)
What are cyclins?
Proteins that bind to specific kinases to regulate events of interphase (cell cycle)
What is MPF?
cyclin M + kinase; Rapid increase of the protein triggers cell entry into Mitosis
Mitosis is made up of what two main stages?
Karyonkinesis-nuclear division and Cytokinesis-division of the cytoplasm
Karyokinesis has how many stages?
4-Prophase, Metaphase, Anaphase, Telophase
Prophase
Chromosomes appear; Nuclear envelope breaks down; Centrosomes separate to opp. poles
Metaphase
Chromosomes migrate to Equatorial Plane; Chromosomes separate into sister chromatids
Band of actin filaments form at equatorial plane; constriction of band separates cytoplasm; begins at anaphase and end in telophase
What is Apoptosis?
Programmed cell death
Apoptosis can occur during what two stages of life?
Embryonic development and Adult Life
Apoptosis in Embryo Develop.
Normal reorganization of tissues; Ex. developing hand & foot once those are completed not all cells used to form are needed
Apoptosis in Adult Life
Occurs to balance cell divisions; removes cells that are damaged or ineffective; Nucleus condenses and breaks up; Does NOT initiate an inflammatory response
