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Chapter 2 - Chapter 2 Life's Chemical Basis Elements...

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Chapter 2 Life’s Chemical Basis Elements Fundamental forms of matter Can’t be broken apart by normal means 92 occur naturally on Earth Most Common Elements in Living Organisms Oxygen Hydrogen Carbon Nitrogen What Are Atoms? Smallest particles that retain properties of an element Made up of subatomic particles: Protons (+) Electrons (-) Neutrons (no charge) Atomic Number Number of protons All atoms of an element have the same atomic number Atomic number of hydrogen = 1 Atomic number of carbon = 6 Mass Number Number of protons + Number of neutrons Isotopes vary in mass number Isotopes Atoms of an element with different numbers of neutrons (different mass numbers) Carbon 12 has 6 protons, 6 neutrons Carbon 14 has 6 protons, 8 neutrons Radioisotopes Have an unstable nucleus that emits energy and particles Radioactive decay transforms radioisotope into a different element Decay occurs at a fixed rate Radioisotopes as Tracers
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Tracer is substance with a radioisotope attached to it Emissions from the tracer can be detected with special devices Following movement of tracers is useful in many areas of biology Radioisotopes in Medicine Positron-Emission Tomography (PET) uses radioisotopes to form images of body tissues Patient is injected with tracer and put through a PET scanner Body cells absorb tracer at different rates Scanner detects radiation caused by energy from decay of the radioisotope, and radiation then forms an image Image can reveal variations and abnormalities in metabolic activity Other Uses of Radioisotopes Drive artificial pacemakers Radiation therapy Emissions from some radioisotopes can destroy cells. Some radioisotopes are used to kill small cancers.
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