lec 1a - Lecture 2 Chemical Foundations I Life occurs in a...

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Lecture 2: Chemical Foundations I
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Biomolecules can be classified as: Hydrophilic Hydrophobic Amphipathic Life occurs in a watery environment sugars fats phospholipids
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Atomic bonds and molecular interactions Covalent bonds : strong bonds, small distance between atoms Noncovalent interactions : weaker, larger distance
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Covalent bonds
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Polar/nonpolar bonds Nonpolar: C-C, C-H Polar: O-H, C-O, N-H, P- O, …. O H C H
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Polar bonds: resonance hybrid H 3 PO 4
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Water is a polar molecule = electric dipole
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Covalent bonds >> noncovalent interactions !! in water !!
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Phosphoanhydre bonds of ATP Free energy ( G o’ ) for hydrolysis = -7.3 kcal
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Covalent bonds >> noncovalent interactions !! in water !!
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Single noncovalent interactions are unstable at 25-37 o C = dynamic!! Multiple noncovalent interactions can create strong and specific associations
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Ionic interactions Hydrogen bonds Van der Waals interactions Hydrophobic effext Noncovalent interactions:
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Noncovalent interactions: Ionic interactions - + + - + + - - + NaCl + + H 2 0 - strong interaction weak interaction “hydration shell” must be removed for direct interaction with protein
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Noncovalent interactions: Ionic interactions + long distance electrostatic forces between charges Attraction between anions and cations is diminished by the hydration layers (which keep ions apart) Hydration layers are made of water molecules interacting with ions through weak chemical bonds: + Water molecules tightly bound to ion = hydration layer Water molecules with looser hydrogen bonds with neighbors = move more freely - Electrons from O of water partly shared with cation Hydrogen bond
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Noncovalent interactions: Ionic interactions - + close contact protein-protein: water excluded = strong interaction
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Hydration shell and selectivity of ion K + channels
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Hydration shell and selectivity of ion K+ channels
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