Cell Cycle All cells go through the cell cycle, some faster than others.

Limits to Cell Size  Diffusion –Limit to the rate at which O 2 & CO 2 can diffuse into and out of cell  DNA –Code for Proteins –Can only translate into proteins SO fast  Surface Area to Volume Ratio –The volume of a cell increases faster than the surface area (see diffusion)

Interphase  A cell spends MOST of its life here.  During interphase it: –Grows back to full size –Does its JOB!!! –Copies DNA –Gets ready to divide (if it is going to)

Interphase  Remember: –Most of the time DNA is “unwound” as chromatin so it can be “read”. Prior to cell division it condenses into visible chromosomes.

Mitosis  A process in which the cell’s chromosomes separate into two(2) new nuclei.  (the chromosomes duplicate before dividing)

Prophase  Chromosomes condense (appear)  Nuclear membrane dissolves  Centrioles move to poles  Spindles begin to form

Metaphase  Chromosomes line up at “equator”  Spindles attach to centromere of each chromosome  Spindles attach to centrioles (in animal cells)  Ready to Divide!

Anaphase  Centromere splits  Chromosome divides into sister chromatids  Chromatids begin to move towards “poles” as spindles shorten

Telophase  Chromosomes arrive at ends of cell  Chromosomes unwind  Nuclear membrane reforms  Nucleolus reappears

Cytokinesis  Cell Membrane pinches inward  Organelles distribute between two new cells  In plant cells a new cell wall grows between the cells  EACH NEW CELL HAS A COMPLETE SET OF DNA