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Cell Cycle All cells go through the cell cycle, some faster than others. Limits to Cell Size Diffusion – Limit to the rate at which O2 & CO2 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
