The Cell Cycle and The Cell Cycle and MitosisMitosis

Why Do Cells Divide?

Why Do Cells Divide

1. Healing and Tissue Repair An average human looses 105 pounds of

dead skin cells in their life Every second, millions of your body cells

are injured or die and must be replaced Replacement of dead cells also occurs in

plants

Why Do Cells Divide

2. Growth All plants and animals begin life as a single

cell Only two ways for an organism to grow: 1)

single cell gets bigger; or 2) the single cell divides into more cells

Why Do Cells Divide One of the most important jobs of a cell is

to exchange materials with its environment (the body or outside world)

The cell needs to get food and nutrients in and waste out

Why Do Cells Divide Why Don’t Cells Just Keep Getting Bigger?

Eventually a cell will reach a size where it will not be able to get enough exchange of materials to sustain cell function

Why Do Cells Divide

3. Perpetuate Life Important for unicellular (prokaryotes)

organisms like bacteria – creates 2 new organisms

Why Do Cells Divide

3. Perpetuate Life Also essential for reproduction of multicellular

organisms

The Cell Cycle The repeating cycle in the life of a cell Interphase: when a cell is preparing for cell

division; this is the majority of the time Mitosis: the process of 1 cell dividing into 2

cells

Interphase First Growth Phase (G1)

Period of growth for a cell Produces new proteins and organelles

Synthesis Phase (S) Cell synthesizes entire copy of DNA

Second Growth Phase (G2) – shortest phase

Cell produces organelles and structures for cell division

Mitosis Remember IPMAT Interphase, Prophase, Metaphase,

Anaphase, Telophase Get a textbook and describe each phase of

mitosis along with a picture (pg. 30-32) Also define cytokinesis and apoptosis

Homework

1. Describe the events in the cell cycle.

2. Explain how mitosis ensures genetic continuity.

3. How does mitosis make the growth and repair of cells possible in an organism?

4. Mitosis Webquest (available on class website)