24 - Friday Lecture 24 Announcements 1 In case you were sick make-up exam SUNDAY 10/24 noon 2:30PM in Biotech rooms Carbohydrates Structural roles

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Friday October 22, 2010 Lecture 24 Announcements 1. In case you were sick: make-up exam SUNDAY 10/24 noon - 2:30PM in Biotech rooms. Carbohydrates Structural roles Recognition Intro to bioenergetics: "high energy" compounds This discussion of high energy compounds is a discussion of G o . Another way to think of this discussion is that we consider, molecule by molecule, how the products are more stable than the reactants. For example, we note the excellent resonance stabilization of a phosphate. This molecule-by-molecule comparison is identical to saying, "we keep the concentration of reactants and of products the same, at 1 Molar". Molecule by molecule comparison is the same as keeping the concentrations the same! Today's lecture At the bottom of page 173, we note a few facts about standard states: . Often, we choose 1.0M as standard state. . But, for protons, biochemists always choose 10 -7 M. We indicate this convention by “marking” G o , as G o ' . . For a pure substance, we choose the concentration of the pure substance. . For reactions in water, we usually omit the [H 2 O], since it is essentially identical to its standard state value, even when it is a participant in the rxn. **Your text uses a convention in which concentrations of H + and some other ions are not shown explicitly, and units are allowed in log terms. Very unfortunate! This kind of nonsense gives biochemists a bad name. Ignore pp. 491-2 of your text, but do note that your text uses the non-standard terminology, G' o instead of G o ' . As an example of how to calculate G o ' , look at the hydrolysis of ATP: ATP + H 2 O ADP + P i + H +
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If all reactants and products are in their standard states, we get the equation shown at the bottom of p. 173, and since every term in both numerator and denominator is unity, then G = G o ' + RT ln(1) = G o ' See the top of page 174 for the hydrolysis of ATP at equilibrium. For ATP hydrolysis, K
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This note was uploaded on 12/10/2011 for the course BCHEM 3350 taught by Professor Feig during the Fall '09 term at Cornell University (Engineering School).

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24 - Friday Lecture 24 Announcements 1 In case you were sick make-up exam SUNDAY 10/24 noon 2:30PM in Biotech rooms Carbohydrates Structural roles

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