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Bioenergetics and Biochemical Reaction Types
1. Entropy Changes during Egg Development Consider a system consisting of an egg in an incubator. The white and yolk of the egg contain proteins, carbohydrates, and lipids. If fertilized, the egg is transformed from a single cell to a complex organism. Discuss this irreversible process in terms of the entropy changes in the system, surroundings, and universe. Be sure that you first clearly define the system and surroundings. Answer Consider the developing chick as the system. The nutrients, egg shell, and outside world are the surroundings. Transformation of the single cell into a chick drastically reduces the entropy of the system (increases the order). Initially, the parts of the egg outside the embryo (within the surroundings) contain complex fuel molecules (a low-entropy condition). During incubation, some of these complex molecules are converted to large numbers of CO2 and H2O molecules (high entropy). This increase in entropy of the surroundings is larger than the decrease in entropy of the chick (the system). Thus, the entropy of the universe (the system surroundings) increases. 2. Calculation of G from an Equilibrium Constant Calculate the standard free-energy change for each of the following metabolically important enzyme-catalyzed reactions, using the equilibrium constants given for the reactions at 25 C and pH 7.0.
oxaloacetate 888888888888z aspartate y88888888888
triose phosphate isomerase
(b) Dihydroxyacetone phosphate 888888888888z glyceraldehyde 3-phosphate y88888888888
K eq ADP
0.0475 K eq 254
(c) Fructose 6-phosphate Answer
8888888z ATP 8888888 y888888888888 fructose 1,6-bisphosphate 8
RT ln [products]/[reactants] 0 and Q K...