Chapter 10 Cell Growth & Division

10-1 Cell Growth Limits –The larger a cell becomes, the more demand it places on the cell’s DNA. –The Cell has more trouble moving enough nutrients & waste across the cell membrane Surface Area-to-Volume Ratio –Volume increases much faster than surface area. –Causes the surface area to volume ratio to decrease.

Cell Division –A cell will divide into 2 “daughter cells” before it becomes too large. –Before Cell Division occurs, the cell must copy all of its DNA. –This gives each “daughter cell” an exact copy of the original cell’s DNA.

10-2: Cell Division Chromosomes Made of DNA (Carries genetic information) 1.Only visible during cell division. 2.Copied before the cell divides. 3.When visible, each chromosome consists of 2 identical sister chromatids. 4.Attached in the center by a centromere.

Before Replication After Replication Chromosomes Sister chromatids Centromere

The Cell Cycle A.Interphase 1.G 1 Phase-Cell growth 2.S-phase- DNA replicates 3.G 2 Phase- Prepare for Mitosis B.M-Phase 1.Mitosis a.Prophase b.Metaphase c.Anaphase d.Telophase 2.Cytokinesis

Cytokinesis- division of the cytoplasm –Animal cells-cytoplasm pinches in until 2 cells are formed –Plant cells- cell plate forms midway between the divided nuclei. (Eventually becomes the cell wall)

10-3 Regulating the Cell Cycle Controls on cell division –Cells at the edge of an injury are stimulated & divide rapidly –Division slows down when the healing process ends.

Cell Regulators Internal Regulators –Proteins that respond to events inside the cell. –Cyclins-regulate the timing of the cell cycle in eukaryotic cells. External Regulators –Direct cells to speed up or slow down the cell cycle.

Cancer A disorder in which some of the body’s own cells loose the ability to control growth. Change in 1 or more of the genes controlling the production of enzymes involved in the cell cycle. –Expressed as cancer when environmental factors trigger the damaged genes into action. –Forms masses of tissues called Tumors that deprive normal cells of nutrients & can damage the surrounding tissue.

Cancer Cont. Final Stage- –Cancer cells enter the circulatory system, spread throughout the body, forming new tumors that disrupt organ function. Enzymes- –Monitor the cell’s progress from phase to phase of the cell cycle. –Can trigger or inhibit the progression of the cell cycle.

Cancer Cont. Contact inhibition- –Cell-to-cell communication to know when to stop dividing. Normal Cells- Have Contact Inhibition (know when to stop dividing) Cancer cells- Loose ability of Contact Inhibition (do not realize the are in contact with each other and continue to divide).

Normal Cells Cancer Cells