Chapter 10: Cell Growth and Division

Limits to Cell Growth

1. DNA “overload”- the larger the cell, the greater demand it places on its DNA

2. Exchanging materials- the larger the cell, the more trouble it has enough oxygen and nutrients in and waste products out

3. Ratio of Surface Area to Volume: cell volume increases more rapidly than surface area causing the ratio of surface area to volume to decrease

4. Cell Division: before a cell becomes too large, it divides into 2 daughter cells each with a complete set of DNA; it also solves the problem of increasing size by reducing cell volume

Chromosomes-made of DNA

• Chromatids: copies of chromosomes (each replicated chromosome has 2)

• Centromere: connects the 2 sister chromatids

The cells of every organism have a specific number of chromosomes.

• Humans have 23 pairs of 46 total chromosomes

The Cell Cycle

Interphase: consists of 3 parts G1 Cells grows

S DNA replication

G2 many organelles & molecules required for division are produced

https://study-biology.wikispaces.com/file/view/mitosis_stage.png/

4 phases (PMAT)

Prophase: • centrioles appear &

move to opposite ends of the cell

• Spindle fibers form • Nuclear membrane

breaks down

Centrioles

Spindle Fibers

Nuclear Membrane

Metaphase

• Chromatids attach to the spindle fibers at the centromere

• Chromosome line up across the center of the cell

Anaphase

• Sister chromatids separate into individual chromosomes

• Chromosomes move to opposite ends of the cell

Telophase

• 2 nuclei form • Chromosomes

uncoil • 2 nuclear

membranes form

Cytokinesis: cytoplasm splits in half

Animal Cells Plant Cells•Cell membrane pinches inward until cytoplasm is split into 2 equal parts

•A cell plate forms between the 2 nuclei • It eventually develops into a cell wall

Regulating the Cell Cycle !

• Controlled by different genes• Proto-oncogenes stimulate cells to divide • Tumor supressor genes prevent cells from

dividing uncontrollably

Uncontrolled Cell Growth

• When genes that regulate the cell cycle are damaged, cells divided uncontrollably

• Tumors (a mass of growing tissue) can be benign or malignant

https://thetruthaboutcancer.com/benign-malignant-tumors-difference/

http://www.aicr.org/cancer-research-update/2014/october_01/cru_Report-Half-of-Cancer-Deaths-are-Preventable.html

http://cancerprogressreport.org/Slides/Fig04_CPR15.jpg