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?