All organisms, including humans, have the ability to regenerate something in the body. Cells must divide and specialize to replace a lost limb. Chapter 10 Mystery
How many cells are in a typical adult human? • What process makes those cells different or unique (special) from one another? 2 terms
Why do cells divide? • The nucleus is not big enough to control a bigger cell. • The cell membrane’s surface area is not large enough to get food and expel waste for a bigger cell • growth • repair/replacement of injured or worn-out parts SURFACE-TO-VOLUME RATIO - Do the quick lab on page 275.
cell division liver cell undergoing cell division splits into two daughter cells
What very important step must occur prior to cell division? • cell replicates, or copies, all of its DNA so that each daughter cell will get one complete set of genetic information
chromosome number • species specific • fruit flies - 8 • human cells - 46 • carrot cells - 18
cell division • when a cell forms 2 “daughter” cells
essay question • How do all cells get a copy of the genetic code?
Mitosis vs. Meiosis http://www.pbs.org/wgbh/nova/miracle/divide.html
asexual reproduction • In 1-celled organisms, cell division is also reproduction called binary fission.
sexual reproduction • fertilization • pollination
Why can bacterial infections spread so rapidly? • genetically identical offspring are made by cell division • one parent
slower able to adapt in a changing environment genetically unique offspring two parents must find one another to mate • faster • take full advantage of a good environment • genetically identical offspring • only one parent
bacterial chromosomes and plasmids Plasmids carry between 2 and 30 genes. Some seem to have the ability to move in and out of the bacterial chromosome.
Describe the life cycle of a typical cell. What are the phases of the cycle, and what is happening in each phase? What happens when the cell cycle is out of control?
The Cell Cycle
Not all cells go through the cell cycle at the same rate. • heart cells – typically don’t divide • brain cells – typically don’t divide • bone marrow cells – divide rapidly
cyclins - proteins that regulate the cell cyclea protein that when injected into a non-dividing cell, would cause a mitotic spindle to form • internal regulators – respond to factors inside the cell • won’t begin mitosis until chromosomes replicate • won’t begin anaphase until chromosomes attached to spindle • external regulators – respond to factors outside the cell • growth factors - initiate cell division embryonic development and wound healing - stop cell division
contact inhibition • most cells grow and divide until they touch another cell • controls on cell growth and cell division can be turned on and off
apoptosis - programmed cell death two different reasons. • needed for proper development Examples: • The resorption of the tadpole tail • The formation of the fingers and toes of the fetus requires the removal of the tissue between them. • The sloughing off of the inner lining of the uterus at the start of menstruation • The formation of the proper connections between neurons in the brain 2. to destroy cells that represent a threat Examples: • Cells infected with viruses • Cells with DNA damage • Cancer cells
tumor - neoplasm • mass or growth of cells 1. benign • encapsulated • slow-growing • compacted (noninvasive) • seldom kill • malignant – cancerous • spreads to surrounding tissues and uses nutrients • prevents proper functioning
Explain how the DNA is your code. What does it code for? How does the code work? What happens if there is a mistake in the code?
What Is Cancer? • actually refers to many diseases • there are more than 100 types of diseases known collectively as cancer • overgrowth of cells • also known as malignancy • doctors who specialize in treating people with cancer are called oncologists
CARCINOGENS – GENERATE CANCER • tobacco, radiation exposure, and even viral infection mutagens – generate mutations Spit tobacco contains 28 known carcinogens. These include formaldehyde, arsenic, cyanide, nickel, and polonium-210.