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gen bio Chapter 2

gen bio Chapter 2 - Chapter 2 atoms and molecules the...

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Chapter 2 – atoms and molecules: the chemical basis of life Elements are substances that canot be broken down into simpler substances by chemical reaction Carbon, hydrogen, oxygen, and mitrogen are the most abundance elements in living things Ca2+, phosparate ? Element Functions - Carbon o Backbone of organize molecules - Hydrogen and oxygen o Components of water - Nitrogen o Component of proteins and nucleic acids Atom - An atom is defined as the smallest portion of an element that retains its chemical properties o Nucleaus Protons Neutrons o Electrons Encircle the nucleus Negative o In an electrically neutral aton- the # of protons = # of neutrons Atomic Number and Mass - Atomic number of an atom is the # of protons in that atom - Atomic mass is the sum of protons and neutrons Ex. If Oxygen has 8 protons and 8 neutrons - Atomic number is 8 - Atomic mass is 16n amu or daltons AMU - Atomic mass unit o Mass of a single proton or neutron - Mass of an electron o 5.489 x 10(-4) amu o 1/1836 th of a proton or 9.109 x 10(-31) kg - An element is a substance that consists of only one type of atom o Iron contains iron atoms Isotopes - If the same element has the same # of protons and electron; but differs by its neutron content, it is called an ISOTOPE - All isotopes of a given element have: the same characteristics, same atomic number, but different atomic masses - Unstable isotopes break down (decay) to stable isotopes o Emit radiation as beta particles - Emission of beta particles can be used in:
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o Radiotheraphy: interferes with cell division o Diagnosis: can be captured using autoradiography (dark grains on a photographic plate) o Measurement of actively synthesizing cells Autoradiography - Active DNA synthesis - Tritium is a radioactive isotope of hydrogen that decays into helium and emits low energy beta particles Orbitals - Electrons move rapidly in electron orbitals o Outside the nucleus - Electron shell o Electrons in each orbinal are at the same principal energy level
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gen bio Chapter 2 - Chapter 2 atoms and molecules the...

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