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
MITOSISMITOSIS
Cell Growth and DivisionCell Growth and Division
2. Why do cells divide?2. Why do cells divide?
If the cell is too big:If the cell is too big: Too much demand is placed DNAToo much demand is placed DNA Harder to move enough nutrients and wastes Harder to move enough nutrients and wastes
across the cell membraneacross the cell membrane
Surface area vs. volumeSurface area vs. volume
4. 4. Surface Area vs. VolumeSurface Area vs. Volume
As a cell increases in size, volume As a cell increases in size, volume increases faster than surface areaincreases faster than surface area
This causes the ratio of surface area to This causes the ratio of surface area to volume to decrease.volume to decrease.
This is a serious problem for the cell and is This is a serious problem for the cell and is why the cell cannot grow any larger than it why the cell cannot grow any larger than it does.does.
5. Cell division solves those 5. Cell division solves those problemsproblems
Before a cell becomes too large, a growing Before a cell becomes too large, a growing cell replicates its DNA and then divides into cell replicates its DNA and then divides into two new “daughter” cells. This is called two new “daughter” cells. This is called mitosis.mitosis.
Cell CycleCell Cycle
http://www.cellsalive.com/mitosis.htm
http://www.johnkyrk.com/mitosis.html
Mitosis versus Meiosis FoldableMitosis versus Meiosis Foldable
Main Events of a Cell CycleMain Events of a Cell Cycle
Interphase Interphase G1, G1, G2, G2, G3G3
M PhaseM Phase ProphaseProphase Metaphase Metaphase AnaphaseAnaphase TelophaseTelophase
http://www.cellsalive.com/mitosis.htm
InterphaseInterphase
The cell grows and The cell grows and replicates its DNAreplicates its DNA
Chromosomes are Chromosomes are not visible, only not visible, only chromatinchromatin
ProphaseProphase
Chromatin condenses Chromatin condenses into chromosomesinto chromosomes
Centrioles separateCentrioles separate Nuclear envelope Nuclear envelope
breaks downbreaks down
MetaphaseMetaphase
Chromosomes line Chromosomes line up across the center up across the center of the cellof the cell
AnaphaseAnaphase
Chromosomes are Chromosomes are pulled apart by pulled apart by spindle into spindle into individual individual chromatidschromatids
TelophaseTelophase
Chromosomes gather at Chromosomes gather at opposite ends of the cellopposite ends of the cell
Two new nuclear Two new nuclear envelopes formenvelopes form
CytokinesisCytokinesis The cytoplasm pinches The cytoplasm pinches
in halfin half Plants lay down a cell Plants lay down a cell
plateplate Two new cells now exist.Two new cells now exist.
http://www.johnkyrk.com/mitosis.html
Label the stages #7Label the stages #7
What stops cell from growing?What stops cell from growing?
Proximity to neighbor cells.Proximity to neighbor cells. Cells in a petri dish will continue to grow until Cells in a petri dish will continue to grow until
they come into contact with other cells.they come into contact with other cells. Similarily, skin around a wound. Similarily, skin around a wound.
Which chemicals regulate the cell Which chemicals regulate the cell cycle?cycle?
How do cells respond to contact How do cells respond to contact with other cells?with other cells?
How are cancer cells different from How are cancer cells different from other cells?other cells?