Why Must Cells Divide? Size Limitation Surface area to volume ratio Substance transport efficiency Cellular communications If urgent signals sent to organelles are not received quick enough, cell could die

The Cell Cycle INTERPHASE (90% of cell cycle) The process of a cell growing and dividing 5 Stages of the cell cycle: G1 Phase - Cell GROWS and performs normal functions S Phase - SYNTHESIS of DNA (DNA is replicated) G2 Phase - Cell prepares for mitosis by making specialized proteins, and taking inventory of cell ALSO KNOWN AS INTERPHASE (90% of cell cycle)

The Cell Cycle Continued…. 4. Mitosis - Nuclear division Prophase Metaphase Anaphase Telophase 5. Cytokinesis - Cellular division into 2 identical daughter cells

MITOSIS: PMAT Nuclear division in Eukaryotic cells Equal separation of genetic info Results in 2 identical “daughter cells” New cells allow for growth and replacement of damaged cells

Prophase Nuclear membrane disappears Nucleolus disappears Chromatin condenses into chromosomes or sister chromatids Spindle apparatus begins to form: spindle fibers, centrioles, and aster fibers Longest phase of Mitosis

Metaphase Spindle pulls and pushes the centromeres until the chromosomes are lined up across the equator Ensures both new cells receive correct chromosomes Shortest phase

Anaphase Spindle apparatus shortens causing the sister chromatids to separate and move to opposite sides of the cell

Telophase Chromosomes arrive at opposite poles Chromosomes uncoil into chromatin Two nuclear membranes begin to form around chromosomes Spindle apparatus disintegrates Nucleolus reforms

Cytokinesis Pinching or constricting of the cytoplasm in animal cells Area of constriction called “furrow” Forms a new cell plate or cell wall in plant cells Separates the 2 new identical daughter cells

Which Phase of the cell cycle?