Cell cycle

Stages of cell cycle

  • interphase

    • duration 90%

    • G1, S, G2

  • M

    • mitosis and cytokinesis


  • cell cycle


  • cell cycle detailed


Interphase

  • when the cell is not dividing

  • carrying out normal cellular functions

  • eukaryotic cells have DNA in nucleus

  • chromosomes are uncoiled chromatin so cannot be seen

  • DNA and centrioles all replicated

  • replication of cell organelles eg. mitochondria occurs in the cytoplasm


Stages of interphase

  • G1: first growth phase

    • protein synthesis

    • synthesis of organelles and cytoplasm

  • S: synthesis

    • DNA replication

  • G2: second growth phase

    • cell organelles grow and divide

    • cell builds energy stores

    • duplicated DNA is checked for errors

  • (mitosis)

    • M - mitosis: nucleus divides

    • C - cytokinesis: cytoplasm/cell divides


  • cell cycle chromosomes


G0

  • why cells may enter G0

    • become differentiated/specialised

    • DNA is damaged

    • become senescent

  • lymphocytes can restart the cell cycle once in G0


Controlling the cell cycle

  • protein complexes determine when the cell enters each stage of the cell cycle

  • checkpoints in G1, G2 and M


  • checkpoints



  • checkpoints function


Control of cell cycle checkpoints

  • the formation of protein complexes determines whether the checkpoints are passed

  • enzyme

    • cyclin dependent kinase (CDK)

  • activating protein

    • cyclin

  1. cyclin binds to inactive CDK enzyme

  2. CDK enzyme activated

  3. CDK phosphorylates other proteins

  4. checkpoint passed


  • action of CDK