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Biology October 3-4 Test Debrief Osmosis lab debrief Mitosis HW: Study TX pgs. 250 – 252 Do 1-8 on SG 269 Do 1-15 on SG 270. MITOSIS. Cell Growth and Division. 2. Why do cells divide?. If the cell is too big: Too much demand is placed DNA
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Biology October 3-4 • Test Debrief • Osmosis lab debrief • Mitosis • HW: Study TX pgs. • 250 – 252 • Do 1-8 on SG 269 • Do 1-15 on SG 270
MITOSIS Cell Growth and Division
2. Why do cells divide? • If the cell is too big: • Too much demand is placed DNA • Harder to move enough nutrients and wastes across the cell membrane
4. Surface Area vs. Volume • As a cell increases in size, volume increases faster than surface area • This causes the ratio of surface area to volume to decrease. • This is a serious problem for the cell and is why the cell cannot grow any larger than it does.
5. Cell division solves those problems • Before a cell becomes too large, a growing cell replicates its DNA and then divides into two new “daughter” cells. This is called mitosis.
Cell Cycle • http://www.cellsalive.com/mitosis.htm • http://www.johnkyrk.com/mitosis.html
Main Events of a Cell Cycle • Interphase • G1, • G2, • G3 • M Phase • Prophase • Metaphase • Anaphase • Telophase • http://www.cellsalive.com/mitosis.htm
Interphase • The cell grows and replicates its DNA • Chromosomes are not visible, only chromatin
Prophase • Chromatin condenses into chromosomes • Centrioles separate • Nuclear envelope breaks down
Metaphase • Chromosomes line up across the center of the cell
Anaphase • Chromosomes are pulled apart by spindle into individual chromatids
Telophase • Chromosomes gather at opposite ends of the cell • Two new nuclear envelopes form
http://www.johnkyrk.com/mitosis.html Cytokinesis • The cytoplasm pinches in half • Plants lay down a cell plate • Two new cells now exist.
What stops cell from growing? • Proximity to neighbor cells. • Cells in a petri dish will continue to grow until they come into contact with other cells. • Similarily, skin around a wound.