22 - BIO 311C Spring 2010 Lecture 22 – Wednesday 24 Mar....

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Unformatted text preview: BIO 311C Spring 2010 Lecture 22 – Wednesday 24 Mar. 1 The formation of a acid anhydride bond from two phosphoric acid functional groups in a dehydration reaction under standard conditions requires an input of approximately 30 kJ/mole of energy, twice the amount of energy that is required in the formation of an ester bond. The formation of ATP from ADP + P i also requires approx. 30 kJ/mole of energy under standard conditions. * AMP + P i ADP + H 2 O Δ G° ≈ + 30 kJ/mole Dehydration rx. Consider the formation of ADP H 2 O Acid anhydride bond formation Now consider some hydrolysis reactions, the reverse of dehydration reactions. Hydrolysis of an acid anhydride bond releases about twice as much energy as does the hydrolysis of an ester bond. * NH 2 N N N N O CH 2 O OH OH P ~ P ~ P acid anhydride bonds ("high-energy" bonds) ester bond Hydrolyses of each of the acid anhydride bonds of ATP releases about twice as much energy as does hydrolyses of the ester bond. ATP * Reactions which release more than approximately 20 kJ/mole of energy produce a large enough amount of energy that some of the energy released during the reaction may be captured to perform useful work in a cell. The reverse of these reactions requires special mechanisms since they require the input of over 20 kJ/mole of energy. ATP is sometimes called the "energy currency" of cells since its hydrolysis to ADP or AMP is used extensively to provide energy for cellular processes. * The Energy Currency of Cells 2 + + + + Δ G° ≈ ¡- 30¡kJ/mole Δ G° ≈ ¡- 15¡kJ/mole Δ G° ≈ ¡- 30¡kJ/mole Δ G° ≈ ¡- 30¡kJ/mole Δ G° ≈ ¡- 30¡kJ/mole * Review Practice Problems Suppose a large number of molecules X are placed into solution and a pathway exists to convert X into Y. The reaction is allowed to come to equilibrium under standard conditions, after which there are 1,000 times as many molecules Y as molecules X in the solutions. Then: a. What is K eq for the reaction X...
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This note was uploaded on 08/29/2010 for the course BIO 49720 taught by Professor Brand during the Spring '10 term at University of Texas.

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22 - BIO 311C Spring 2010 Lecture 22 – Wednesday 24 Mar....

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