a. Draw out the pathways described above. Provide accurate line drawings for each lipid described b. For each step, identify if an elongase and/or desaturase is used. If a desaturase is used, indicate the type (for example  9 desaturase). c. For each step indicate whether the parasite could be using an enzyme from the human host to complete the step. Briefly justify your choices. d. This pathway is being considered as a parasite-specific target for drugs (to treat parasitic infections). Which step would you choose to target and why?

Using the ActiveModel for enoyl-CoA dehydratase, give an example of a case in which conserved residues in slightly different positions can change the catalytic rate of reaction.

Examine the ActiveModel for alcohol dehydrogenase and describe the structure and function of the catalytic zinc center.

Which of the following statements about the allosteric site is true? a. The allosteric site is a second active site on a substrate in a metabolic pathway. b. The allosteric site on an enzyme can allow the product of a metabolic pathway to inhibit that enzyme and stop the pathway. c. When the allosteric site of an enzyme is occupied, the reaction is irreversible and the enzyme cannot react again. d. An allosteric activator prevents binding at the active site. e. An enzyme that possesses allosteric sites does not possess an active site.

In an enzymatic reaction: a. the enzyme leaves the reaction chemically unchanged. b. if the enzyme molecules approach maximal rate, and the substrate is continually increased, the rate of the reaction does not reach saturation. c. in the stomach, enzymes would have an optimal activity at a neutral pH. d. increasing temperature above the optimal value slows the reaction rate. e. the least important level of organization for an enzyme is its tertiary structure.

Why Do Anabolic and Catabolic Pathways Differ? Why is the pathway for the biosynthesis of a biomolecule at least partially different from the pathway for its catabolism? Why is the pathway for the biosynthesis of a biomolecule inherently more complex than the pathway for its degradation?

PREDICT In the following reaction series, which enzyme(s) is/are most likely to have an allosteric site to which the end product E binds? (a) enzyme 1 (b) enzyme 2 (c) enzyme 3 (d) enzyme 4 (e) enzymes 3 and 4

Distinguishing the Mechanisms of Class I and Class I Aldolases Fructose bisphosphate aldolase in animal muscle is a class 1 aldolase, which forms a Schiff base intermediate between substrate (for example. fructose-1, 6-bisphosphate or dihydroxyacetone phosphate) and a lysine at the active site (see Figure I8.12). The chemical evidence for this intermediate conies from studies with aldolase and the reducing agent sodium borohydride, NaBH4. Incubation of the enzyme with dihydroxyacetone phosphate and NaBH4 inactivates the enzyme. Interestingly, no inactivation is observed if NabH4 is added to the enzyme in the absence of substrate. Write a mechanism that explains these observations and provides evidence for the formation of a Schiff base intermediate in the aldolase reaction.

Using the answer code on the right, indicate which form of energy production is being described: 1. takes place in the mitochondrial matrix 2. produces H2O as a by-product 3. results in a rich yield of ATP 4. takes place in the cytosol 5. processes acetyl-CoA 6. takes place in the mitochondrial innermembrane cristae 7. converts glucose into two pyruvate molecules 8. uses molecular oxygen 9. accomplished by the electron transport system and ATP synthase (a) glycolysis (b) citric acid cycle (c) oxidative phosphorylation

Consider the synthesis and degradation of tyrosine as shown in Figures 25.37, 25.38, and 25.48 to determine where the carbon atoms in PEP and erythrose-4-P would end up in acetoacetate and fumarate.