Why do cells need to divide? Cell Size Limitations Why do cells need to divide? Surface area to volume ratio Plasma membrane relative to cell volume Transport of substances More efficient in smaller cells Cellular communications If urgent signals sent to organelles are not received quick enough, cell could die

Cell Cycle INTERPHASE 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

Cell Cycle Continued…. 4. Mitosis= Nuclear division (4 phases) 5. Cytokinesis= Cellular division into 2 identical daughter cells

MITOSIS Nuclear division in Eukaryotic cells Equal separation of genetic info Results in 2 identical “daughter cells” New cells allow for growth & replacement of damaged cells 4 Stages

Prophase Chromatin condenses into visible chromosomes(fuzzy X’s) Nuclear membrane disappears Centrioles migrate to poles of cell Spindle fibers form Spindle fibers attach to centromeres Spindle apparatus-centrioles & spindle fibers; organize chromosomes during division *Longest phase of Mitosis

Metaphase Chromosomes align at equator (MIDDLE) of cell Pulled to equator by spindle fibers attached to centromeres Ensures both new cells receive correct chromosomes * Shortest phase

Anaphase Chromatids pulled to opposite poles Spindle apparatus shortens causing the separation

Telophase Chromosomes arrive at opposite poles Chromosomes de- condense 2 nuclear membranes begin to form Spindle apparatus disintegrates

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

Cancer Uncontrolled growth and division Failure of regulation during cell cycle