Cell cycle

• 1. Mitosis
  2. Cytokinesis
  3. G1
  4. S
  5. G2

  
• G1, S and G2 are all part of interphase
• Cells divide on a regular basis to bring about growth and asexual reproduction. Cells divide in a sequence of events known as the cell cycle.
• Interphase is a period of non-division when the cells increase in mass and size, carry out normal cellular activities (e.g respiration, protein synthesis) and replicate their DNA, cytoplasm and cell organelles, ready for division.
• The length of the cell cycle is variable
• Gap 1 (G1) is the time between the end of the previous round of mitosis cell division and the start of chromosome replication. The cell takes in material, grows, and develops. This is the time that is most variable. In actively dividing cells, G1, is very short
• S is the stage when chromosomes replicate and become double-stranded chromatids ready for cell division.
• A cell is in the interphase stage of the cell cycle for much of its life.
• During interphase, ATP production is stepped up at times to provide the extra energy needed as the cells divide.
• When everything the cell needs is present, and the parent cell is large enough, interphase ends and mitosis begins
• Gap 2 (G2) is the time that the organelles and other materials needed for cell division are synthesised - before a cell can divide, it needs two of everything
• Mitosis is when the cell is actively dividing.
• The control of the cell cycle is regulated at checkpoints when the cycle moves from one checkpoint to another, by chemical substances which are called cyclins. These build up and attach to enzymes called cyclin-dependent kinases (CDKs). The cyclin-CDK complex that forms phosphorylates, other proteins, changing their shape and bringing about the next stage in the cell cycle
• • the phosphorylates of the chromatin in the nucleus, results in the chromosomes becoming denser
  • the phosphorylation of some proteins in the nuclear membrane which leads to the breakdown of the nuclear membrane during cell division
• In animal cells, a ding of contractile fibres tightens around the centre of the cells, they continue to contract until the two cells have been separated.
• In the cytokinesis of plant cells, a cellulose cell wall will build up from the inside of the cell outwards.
• Cytokinesis is the final stage of the cell cycle and is when the cells separate, and the cytoplasm divides