Chapter 3, Problem 1RT

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.

The process of bulk flow transports fluids in a plant. Describe the two main bulk flow processes.

In answering the previous question, did you use the product rule, the sum rule, or both?

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?

Bruce Ames and his colleagues have pointed out that although detailed toxicological analysis has been conducted on synthetic chemicals, almost no information is available about the mutagenic or carcinogenic effects of the toxins produced by plants as a natural defense against fungi, insects, and animal predators. Tens of thousands of such compounds have been discovered, and he estimates that in the United States adults eat about 1.5 g of these compounds each daylevels that are approximately 10,000 times higher than those of the synthetic pesticides present in the diet. For example, cabbage contains 49 natural pesticides and metabolites, and only a few of these have been tested for their carcinogenic and mutagenic effects. a. With the introduction of new foods into the U.S. diet over the last 200 years (mangoes, kiwi fruit, tomatoes, and so forth), has there been enough time for humans to develop resistance to the mutagenic effects of the toxins present in those foods? b. The natural pesticides present in plants constitute more than 99% of the toxins we eat. Should diet planning, especially for vegetarians, take into account the doses of toxins present in the diet?

Radiotracer Labeling of Pyruvate from Glucose Determine the anticipated location in pyruvate of labeled carbons If glucose molecules labeled (in separate experiments.) with 14C at each position of (.tie carbon skeleton proceed through the glycolytic pathway.

Which of the following methods is not used by enzymes to increase the rate of reactions? a. covalent bonding with the substrate at their active site b. bringing reacting molecules into close prosimity c. orienting reactants into positions to favor transition states d. changing charges on reactants to hasten their reactivity e. increasing fit of enzyme and substrate that reduces the energy of activation

What is the significance that the combined absorption spectra of chlorophylls a and b roughly match the action spectrum of photosynthesis? Would photosynthesis be more efficient if their individual absorption spectra coincided exactly?

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.