chapter2_Lecture - Molecules of Life Chapter 2 Science or...

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Molecules of Life Chapter 2
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Science or Supernatural? Natural hydrocarbons
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Methane Simplest organic molecule A greenhouse gas Main component of natural gas Produced by bacteria in vertebrate gut Found in deep ocean deposits as the world’s single largest carbon store
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Impacts, Issues Video Science or the Supernatural?
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Fig. 2-1, p.16 human body Oxygen 61.0% Carbon 23.0 Hydrogen 10.0 Nitrogen 2.6 Calcium 1.4 Phosphorus 1.1 Potassium 0.2 Sulfur 0.2 earth’s crust Oxygen 46.0% Carbon 27.0 Hydrogen 8.2 Nitrogen 6.3 Calcium 5.0 Phosphorus 2.9 Potassium 2.3 Sulfur 1.5
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Hydrogen Helium electron proton neutron Examples of Atoms
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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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Isotopes Atoms of an element with different numbers of neutrons Behave the same way in chemical reactions Radioisotopes emit particles and energy as they decay, eventually becoming a different element
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What Determines Whether Atoms Will Interact? The number and arrangement of their electrons
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Electrons Carry a negative charge Repel one another Are attracted to protons in the nucleus Move in orbitals (volumes of space that surround the nucleus)
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Electron Orbitals Orbitals can hold up to two electrons Atoms differ in the number of electrons in orbitals Orbitals closest to nucleus are lower energy and are filled first
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hydrogen 1p + , 1e helium 2p + , 2e carbon 6p + , 6e oxygen 8p + , 8e sodium 11p + , 11e chlorine 17p + , 17e Fig. 2-2, p.17 neon 10p + , 10e electron proton neutron The Shell Model
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Shell Model First shell Lowest orbital Holds 2 electrons Second shell 4 orbitals hold up to a total of 8 electrons Unfilled shells make atoms likely to react
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Chemical Bonds, Molecules, and Compounds Bond is union between electron structures of atoms Atoms bond to form molecules Molecules may contain atoms of only one element: O 2 Compounds contain more than one element: H 2 O
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Important Bonds in Biological Molecules Ionic bonds Covalent bonds Hydrogen bonds
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Ionic Bonding One atom loses electrons, becomes positively charged ion Another atom gains these electrons, becomes negatively charged ion Charge difference attracts the two ions to one another
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Formation of NaCl Sodium atom (Na) Outer shell has one electron Chlorine atom (Cl) Outer shell has seven electrons Na transfers electron to Cl, forming Na + and Cl - Ions remain together as NaCl (sodium chloride)
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Fig. 2-3a, p.18 NaCl
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Covalent Bonding Atoms share a pair or pairs of electrons to fill outermost shell Single covalent bond Double covalent bond Triple covalent bond Molecular hydrogen
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Polar or Nonpolar Bonds Nonpolar if atoms share electrons equally Hydrogen gas (H - H) Polar if electrons spend more time near nucleus with most protons Water Electrons more attracted to O nucleus than to H nuclei
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This note was uploaded on 03/12/2011 for the course BIO 1002 taught by Professor Bush during the Fall '08 term at University of Minnesota Morris.

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chapter2_Lecture - Molecules of Life Chapter 2 Science or...

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