Hormones for cell growth and division

1. Hormones for cell growth and division Science 9

2. Differences from one organism to another • Cell growth and cell division are important for understanding differences between organisms of the same species • Cells communicate with one another using chemical messengers • These messengers are called hormones • Hormones are produced in cells in one part of the body and can affect cell division and growth in another part of the body • Some hormones trigger cells to grow and divide

3. Plant growth hormones • Plants produce a variety of growth hormones • Auxins are plant hormones that cause cells to grow longer • Cytokinins are plant hormones that stimulate cell division • They are found in the roots but communicate with all parts of the plant

4. Animal growth hormones • Growth hormone (GH) is produced in the pituitary gland of humans • It is carried by blood to all areas of the body • It does not affect all parts of the body in the same way • Low amounts of GH during childhood can cause dwarfism and high amount can cause gigantism

5. Cell division and Patterns of growth • Humans grow fastest during the nine months before birth and the first three months after • Not all body parts grow at the same rate

6. Aging and cell division • Very few of the cells you were born with are still dividing • Red blood cells live about 120 days • Skin cells are replaced daily • To stay alive, we rely on cell division • There is a limit to how often a cell can divide • Eventually, cells die and are not replaced • Injuries are not repaired • Accumulating damage and the function of organs are compromised