1-423-08Water - What happens when we get too much-drown hyponatremia 9 Ionization of water In pure water[H = 10-7 H H 2 O<> H OH-10 WEAK acids

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1 Biochemistry is chemistry in water; (almost) all life as we know it requires an aqueous environment, within narrow pH and temperature ranges. Therefore, we must always consider the effect of water on all biochemical interactions… Water is a polar molecule Hydrogen bonds
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2 Property of cohesiveness Ice is very ordered: 4 H-bonds/ water molecule in ice
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3 Relatively weak, noncovalent bonds/interactions are critical in biological systems Covalent bond energy = 350-450 kJ/mol
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4 H-bond energy = 8-21 kJ/mol * * * * Electrostatic interactions (ionic bonds) Bond energy = 40-90 kJ/mol
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5 Water weakens electrostatic interactions
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6 Hydrophobic interactions Bond energy = 4-8 kJ/mole Van der Waals interactions Bond energy = 4 kJ/mole All individually weak, thus readily reversible. But many possible, so cumulatively significant
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7 Hydrophilic Hydrophobic Amphipathic Thermal properties of water Any solute will depress freezing pt, raise boiling pt of water
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8 Osmosis What happens when we don’t get enough water? -dehydration, death
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Unformatted text preview: What happens when we get too much?-drown, hyponatremia 9 Ionization of water In pure water, [H + ] = 10-7 H + H 2 O <---> H + + OH-10 WEAK acids and bases in biochemistry… Tendency of an acid to dissociate HA<-> H + + A-is described by K a = ([H + ][A-])/[HA] pK a = -log K a (proton donor) (proton acceptor) High K a , low pK a Low K a , high pK a pK a is the pH at which an acid group is half-dissociated: [HA] = [A-] Also, the midpoint of the buffering region * HH equation: pH = pK a + log [proton acceptor]/ [proton donor] Describes the shape of the titration curve of any weak acid 11 WEAK acids and bases in biochemistry… Tendency of an acid to dissociate HA<-> H + + A-is described by K a = ([H + ][A-])/[HA] pK a = -log K a (proton donor) (proton acceptor) 12 Reality check: pH, pK a pH is a measure of all H + in solution pK a is a measure of the affinity of a dissociable group for its proton...
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This note was uploaded on 04/05/2008 for the course BIOCHEM 423 taught by Professor Osgood during the Spring '08 term at New Mexico.

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1-423-08Water - What happens when we get too much-drown hyponatremia 9 Ionization of water In pure water[H = 10-7 H H 2 O<> H OH-10 WEAK acids

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