Cell Growth and Division Cell Cycle 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

Surface area vs. volume

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, S G2 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

Cytokinesis The cytoplasm pinches in half Plants lay down a cell plate http://www.johnkyrk.com/mitosis.html Cytokinesis The cytoplasm pinches in half Plants lay down a cell plate Two new cells now exist.

Label the stages #7

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.

Which chemicals regulate the cell cycle?

How do cells respond to contact with other cells?

How are cancer cells different from other cells?