25 - BIO 311C Spring 2010 Lecture 25 Wednesday 31 Mar. 1 A...

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Unformatted text preview: BIO 311C Spring 2010 Lecture 25 Wednesday 31 Mar. 1 A metabolic pathway must have a net negative G value in order to progress in the forward direction. However, it is not necessary for every reaction in the pathway to have a negative G value in order for the pathway to proceed in the forward direction. A D B C E 1 E 2 E 3 G 1 = - 8 kJ/mol G 2 = + 9 kJ/mol G 3 = - 14 kJ/mol = (- 8 + 9- 14 ) kJ/mol = - 13 kJ/mol Reaction 1 "pushes" reaction 2 in the forward direction. Reaction 3 "pulls" reaction 2 in the forward direction. * G net = G 1 + G 2 + G 3 3 Most metabolic pathways fall into two broad categories:- Catabolic pathways- Anabolic pathways Catabolic pathways may be described as "breakdown" pathways. Anabolic pathways may be described as "build-up" pathways. * 4 General Characteristics of Catabolic Pathways- Catabolic pathways result in the conversion of relatively large and/or complex initial reactant into smaller and/or simpler final products.- Individual reactions of catabolic pathways often result in a substrate becoming more oxidized as hydrogen atoms are removed.- Individual reactions of catabolic pathways pathway often release enough energy that a portion of the energy can be captured by the synthesis of ATP or can be stored in another form.- The final products of catabolic pathways are generally of less potential value to the cell than was the starting reactant. Not all catabolic pathways display all four of these listed features. * 5 Representation of a Catabolic Pathway ATP [2H] small molecules large initial reactant catabolic pathway small final product * The main value to cells of most catabolic pathways is the capture of energy and reducing units. The small and oxidized final products are often discarded as waste....
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25 - BIO 311C Spring 2010 Lecture 25 Wednesday 31 Mar. 1 A...

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