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Cell Growth and Division The cell cycle and Mitosis. When to Divide? • Diffusion is a limiting factor – Works well over short distances – Takes too long to travel far • Surface area to volume ratio – All nutrients and waste must cross the cell membrane – Larger the cell the smaller the surface area to volume ratio (A larger cell produces more waste, but has less surface area for it to get out of) • DNA is a limiting factor – Most cells have 1 nucleus and 1 set of DNA – If the cell is too Big one copy of the DNA is not enough to make enough proteins for a large cell Diffusion and cell size • Materials move through cells by diffusion. Oxygen and food move into cells, while waste products move out of cells. • The size of a cell affects how efficiently materials get to all parts of a cell. • The larger the cell the less efficient transport of materials across the cell membrane is. Surface area to Volume Ratio Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume • The higher the surface area to volume ratio the easier it is to get nutrients to the cell Prokaryotic cell division • • • • Binary fission DNA replicates No organelles to multiply Cell divides cytoplasm, ribosomes and DNA • Cell wall divides two cells The Cell Cycle G1 phase M phase S phase G2 phase Interphase • Interphase is when the cell is not dividing, but is going about its normal daily business. Ex. Nerve cells send messages, muscle cells contract. – G1- cell growth and day to day life – S -Synthesis- DNA is replicating – G2 –prepare for cell division, make extra copies of organelles so both daughter cells will get all the organelles. Root words • Look up what the following word pre-fixes mean • Inter• Pro• Meta• Ana• Telo- Root Words… Defined • Inter-Between, the cell is between divisions • Pro-Greek, from pro, before, before cells divide they must prepare. • Meta-Greek, from meta, beside, Chromosomes are side by side • Ana- Backward, Chromosomes are pulled back • Telo-From Greek telos, end Correct order… Prophase Interphase Spindle forming Centrioles Nuclear envelope Cytokinesis Chromatin Centriole Centromere Chromosomes (paired chromatids) Spindle Centriole Individual chromosomes Nuclear envelope reforming Anaphase Telophase Metaphase
