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CP Biology Chapter 2The Chemistry of Life
Chemicals make up ALL matter – living and nonliving.• All life processes are chemical reactions.• Chemical signals between cells regulate
metabolism– enzymes, hormones
• Chemical signals in the environment– Attract a mate; attract pollinators– Scare away predators– Find food
Why is chemistry important in the study of biology?
ELEMENTS, ATOMS, AND MOLECULES
There are 92 naturally occurring elements–Only 4 make up most of the human body–CARBON–HYDROGEN (C H O N)- OXYGEN- NITROGEN
Elements of Living Cells
Major elements
Minor elements
LE 2-3
Sodium Chlorine Sodium Chloride
Na
Metal, soft
Highly reactive
Cl
Gas
toxic
Salt
Crystal
Common, edible
Two or more elements in a FIXED RATIO
COMPOUNDS
Elements can combine to form compounds
LE 2-7b
Na+
Cl-
NaCl is ionic - “crystal lattice” structure
What is an isotope?Isotopes are atoms with the same atomic number but different masses
• different number of neutrons
• Behave the same way chemically!!
• Most elements have at least one isotope
Isotopes of Carbon
Isotopes of the same element have the same number of PROTONS and the same number of ELECTRONS.
- have the same chemical behaviors
Radioactive Isotopes
Have unstable nuclei
• Emit atomic particles as the “decay”
• Become a stable atom of a different element
Radioactive isotopes
• Also emit radiation• at a steady rate, called “half-life”
– Half-life: time for ½ of a sample to decay– Ex. Half-life of C-14 is 5700 years
• Can use radiation for many purposes
DATE FOSSILS
Carbon-14 and other isotopes • measure amount of C-14 present in a
fossil• compare to amount present when it died• tells us how old the fossil is
Use as “tags” or “tracers”
• Same chemical properties as stable isotopes• Used the same in life processes• Can show how atoms and molecules are used in
living things– Carbon-14
• showed how plants make food from CO2
– Radioactive sulfur and phosphorus• showed how viruses enter cells
PET Scan - MEDICAL DIAGNOSIS
PET scan = Positron Emission Tomography• Radioisotope in blood collects in tissues• Amount of radiation shows organ function
- more active cells use more food and energy (ex. cancer cells)
- more active cells emit more radiation- ”hot spot”
A thyroid scan showing a “hot spot”
Scan showing increased uptake in thyroid gland
A body scan showing areas of increased radiation
Increased radiation shows abnormal function
PET scans show functionCAT scans show structure
Radiation Therapy – treats cancer External therapy• beam of radiation aimed at tumor• from radioisotope, or from therapy X-ray
machine
Internal Therapy with Radioisotopes
1. Isotope injected into blood - Concentrates in diseased organ and radiation kills some cells 2. Radioactive “seeds” put directly into tumor- Radiation reaches cancer cells without going through healthy tissue
Radioisotopes kill cancer cells
Uses in Industry• Nuclear energy• Sterilize surgery instruments• Kill bacteria in food