Why do Cells Need to Grow? Replace old cells Replace damaged cells Make new life

When do Cells Grow? Cells grow, or more accurately, divide to stay small Cells need to be small to function properly – Cellular organelles need to be able to communicate to each other and the outside world The surface area to volume ratio needs to be high – That means, the cell needs more membrane and less cytoplasm

The Cell Cycle The cycle of growing and dividing of eukaryotic cells It is a continuous production of new cells Controlled by a series of signals Three Main Stages of the Cell Cycle: 1.Interphase 2. Mitosis 3.Cytokinesis

Interphase - The Longest Stage Broken down into Three Sub-Stages 1.G 1 Sub-Stage Period of cell growth and maturing into a functioning cell Some cells, like muscle cells, stop here 2. S Sub-Stage Duplicates its DNA DNA is copied to put into new cell 3. G 2 Sub-Stage Prepares for Division Cell gets ready to divide

Mitosis and Cytokinesis Mitosis – When the nucleus and cellular material divides Cytokinesis – When the cell’s cytoplasm divides

Mitosis The accurate separation of the cell’s DNA 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase

Prophase Longest phase of Mitosis The copied DNA condenses into chromosomes – Chromosomes are shaped like an X – The center of the X is called the centromere – The pair of chromosomes are called sister chromatids Nuclear membrane disintegrates Spindle fibers (microtubules) begin to form

Metaphase Chromosomes attach to spindles (microtubules) Chromosomes align along the equator of the cell

Anaphase The microtubules of the spindles begin to shorten The sister chromatids are pulled apart The chromatids are moved to the poles of the cell

Telophase Chromosomes reach end of cell Nuclear membrane reappears Chromosomes decondense

Cytokinesis Division of the cytoplasm Animal cells – furrow Plant cells – cell plate

Cell Cycle Checkpoints The cell cycle has “checkpoints” “security” proteins at the “checkpoints” If something goes wrong, cell cycle stops Also regulation on when cell cycle starts and stops What is it called when the cell cycle continues uncontrollably?