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Problem solution lec 1-4 2016.pptx

Problem solution lec 1-4 2016.pptx - BIOC 3110 Discussion...

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BIOC 3110 Discussion Section Lectures 1-4 Fall 2016
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Ch.2 Problem #9 How does the second Law of Thermodynamics allow for the formation of biochemical order? 2 nd Law: The total entropy of a system and its surroundings always increases in a spontaneous process.
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Ch.2 Problem #9 How does the second Law of Thermodynamics allow for the formation of biochemical order? 2 nd Law: The total entropy of a system and its surroundings always increases in a spontaneous process. Association of the hydrophobic residues at the core of the protein liberates ordered water molecules, which increases entropy.
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Ch. 2 Problem #10 If an aqueous solution has a hydrogen ion concentration ([H + ]) of 10 -5 M, what is the concentration of the hydroxyl ion ([OH - ])? Equation for self-ionization of water: Rearrange to solve for [OH - ]: Substitute 10 -14 for K w and the given value of 10 -5 for [H + ]: K w [ H ][ OH ] [ OH ] K w [ H ] [ OH ] 10 14 10 5 10 9 M
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Ch. 2 Problem #11 If an aqueous solution has a hydroxyl ion concentration ([OH - ]) of 10 -2 M, what is the concentration of the hydrogen ion ([H + ])? Equation for self-ionization of water: Rearrange to solve for [H + ]: Substitute 10 -14 for K w and the given value of 10 -2 for [OH - ]: K w [ H ][ OH ] [ H ] K w [ OH ] [ H ] 10 14 10 2 10 12 M
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Ch.2 Problem #12 Using the Henderson-Hasselbalch equation, show that, for a weak acid, the pK a is the pH at which the concentration of the acid equals the concentration of the conjugate base. Henderson-Hasselbalch equation: We are given the following conditions: The ration of [A - ] to [HA] is 1, and log(1)=0 The equation reduces to this form: pH pK a log [ A ] [ HA ] [ A ] [ HA ] log [ A ] [ HA ] log 1 0 pH pK a
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Ch.2 Problem #13 What is the relation between the pK a of an acid and the strength of the acid? Stronger (more dissociated) acids have higher K a values: The definition of pK a: Rearranged equation: The same is true for pH and [H + ]: K a [ H ][ A ] [ HA ] pK a log 1 K a pK a   log( K a ) pH   log([ H ])
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Ch.2 Problem #16 For an acid HA, the concentration of HA and A - are 0.075 and 0.025, respectively, at pH 6.0. What is the pK a value for HA? Given information: Henderson-Hasselbalch equation: Solving for pK a : Plugging in values and solving: At pH 6.0: [HA] = 0.075 [A - ]=0.025 pH pK a log [ A ] [ HA ] pK a pH log [ A ] [ HA ] pK a 6.0 log 0.025 0.075 6.48
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Ch.3 Problem #6 In each of the following pairs of amino acids, identify which amino acid would be most soluble in water: a) Ala , Leu
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Ch.3 Problem #6 In each of the following pairs of amino acids, identify which amino acid would be most soluble in water: a) Ala , Leu Smaller carbon chain
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Ch.3 Problem #6 In each of the following pairs of amino acids, identify which amino acid would be most soluble in water: a) Ala , Leu b) Tyr, Phe
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Ch.3 Problem #6 In each of the following pairs of amino acids, identify which amino acid would be most soluble in water: a) Ala , Leu b) Tyr , Phe Can hydrogen bond
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Ch.3 Problem #6
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