Lecture_3_DulaiS09_ALT2

Lecture_3_DulaiS09_ALT2 - Lifes Chemical Basis Chapter 2...

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Life’s Chemical Basis Chapter 2
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Elements • Fundamental forms of matter • Can’t be broken apart by normal means • 92 occur naturally on Earth
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Most Common Elements in Living Organisms Oxygen Hydrogen Carbon Nitrogen
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What Are Atoms? • Smallest particles that retain properties of an element • Made up of subatomic particles: – Protons (+) – Electrons (-) – Neutrons (no charge)
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Representing the Hydrogen Atom electron proton electron Shell model Ball model Electron density cloud
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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
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Mass Number Number of protons + Number of neutrons Isotopes vary in mass number
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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
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Radioisotopes • Have an unstable nucleus that emits energy and particles • Radioactive decay transforms radioisotope into a different element • Decay occurs at a fixed rate
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Radioisotopes as Tracers • 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
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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
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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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What Determines whether Atoms Will Interact?
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This note was uploaded on 11/18/2010 for the course SS 101 taught by Professor Denver during the Spring '10 term at Alabama.

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Lecture_3_DulaiS09_ALT2 - Lifes Chemical Basis Chapter 2...

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