5.1 Cell Cycle Chapter 5 Cell Growth and Division and Growth Mr. Shilala DAHS

KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

The cell cycle has four main stages: gap 1, synthesis, gap 2, and mitosis.. The cell cycle is a regular pattern of growth, DNA replication, and cell division. Stages get their name from early observations –Interphase when a cell was not dividing Improvements in technology led interphase being called –Gap 1,DNA synthesis and Gap 2 Realized during interphase cells carry out normal functions and grow –Mitosis when a cell was dividing

Stages of Cell Cycle 1.Gap 1 (G1): –Cell growth and normal functions –Cell Spends majority of time here –Varies by type of cell –Must pass a critical checkpoint before going to synthesis stage Like passing a physical before participating in sports

2.DNA Synthesis (S) –Cell copies DNA –Cell now contains 2 identical copies of DNA

3.Gap 2 (G 2 ): –Additional growth –Cell is getting ready to divide –Also contains critical checkpoint Undamaged DNA etc 4.Mitosis – division of cell nucleus –Two processes Mitosis Cytokinesis – cytoplasm splitting –Occurs only if the cell is large enough and the DNA undamaged

Cells divide at different rates. The rate of cell division varies widely with the need for those types of cells.

G 0 Stage Stage when a cell reaches a point where it is highly unlikely to divide –Example: Neuron in spinal cord –Lymphocytes – divide only when invader enters body

Cell size is limited and determined by the SA to V ratio. Cells have upper and lower limits Determined by the surface area to Volume ratio.

Surface area must allow for adequate exchange of nutrients. –Cells that must be large have unique shapes To maintain a suitable size cells divide

To maintain a suitable size cells must divide –Must be coordinated Example –If a cell doubles in size before dividing, daughter cells will be twice as large as original cell – eventually cells too large to survive