Biochem (Test 1) 11. Which of the following statements most directly supports the claim that different species of organisms use different metabolic strategies to meet their energy requirements for growth, reproduction, and homeostasis? During cold periods pond-dwelling animals can increase the number of unsaturated fatty acids in their cell membranes while some plants make antifreeze proteins to prevent ice crystal formation in tissue. Bacteria lack introns while many eukaryotic genes contain many of these intervening sequences. Carnivores have more teeth that are specialized for ripping food while herbivores have more teeth that are specialized for grinding food. Plants generally use starch molecules for storage while animals use glycogen and fats for storage.

Biochem (Test 1) 20. Sickle-cell anemia results from a point mutation in the HBB gene. The mutation results in the replacement of an amino acid that has a hydrophilic R-group with an amino acid that has a hydrophobic R-group on the exterior of the hemoglobin protein. Such a mutation would most likely result in altered: properties of the molecule as a result of abnormal interactions between adjacent hemoglobin molecules. DNA structure as a result of abnormal hydrogen bonding between nitrogenous bases. Fatty acid structure as a result of changes in ionic interactions between adjacent fatty acid chains. Protein secondary structure as a result of abnormal hydrophobic interactions between R-groups in the backbone of the protein.

Biochem (Test 1) 22. Testosterone oxido-reductase is a liver enzyme that regulates testosterone levels in alligators. One study compared testosterone oxido-reductase activity between male and female alligators from Lake Woodruff, a relatively pristine environemtn and from Lake Apopka, an area that has suffered severe contamination. The graph below depicts the findings of that study. The data in the graph best support which of the following claims?

Environmental contamination elevates total testosterone oxido-reductase activity in females. Environmental contamination reduces total testosterone oxido-reductase activity in females. Environmental contamination elevates total testosterone oxido-reductase activity in males. Environmental contaminations reduces total testosterone oxido-reductase activity in males.

Bioshem(Test 1) 33-35. Both myoglobin and hemoglobin are proteins that bind reversibly with molecular oxygen. The graph below shows the oxygen binding saturation of each protein at different concentrations of oxygen.

33. Which of the following statements is correct> At 10 mmHg partial pressure, hemoglobin binds to oxygen but myoglobin does not. At 20 mmHg partial pressure, myoglobin and hemoglobin bind oxygen in equal amounts. At 40 mmHg partial pressure, myoglobin has a greater affinity for oxygen than hemoglobin has. At 80 mmHg partial pressure, myoglobin binds twice as much oxygen as hemoglobin does.

34. Strenuous exercise lowers the blood pH, causing the curves for both hemoglobin and myoglobin to shift to the right. This shift results in: a. an unloading of O2 at higher partial pressures. b. an increase in the number of O2 binding sites. c. the capture of more O2 by hemoglobin. d. The capture of more O2 by myoglobin.

35. Which of the following best describes the physiological significance of the different oxygen-binding capabilities of hemoglobin and myoglobin? The prevent muscles from depleting oxygen levels in the b blood. The cause muscles to become anaerobic. They prevent glycogen depletion in muscles. They enhance movement of oxygen from the blood into the muscles.

A substrate that closely resembles the active site of the enzyme. Biochem (Test 2) 51. Enzymes are globular proteins that have either tertiary or quarternary structure. This structure gives them a particular shape that is maintained as long as the environment of the enzyme remains stable. For an enzyme to be a productive catalyst for reactions, which of the following is required? A substrate that can be forced to fit into an allosteric site on the enzyme. A substrate that closely resembles the active site of the enzyme. An allosteric site that can be modified so that the substrate will fit into it. An enzyme with tertiary structure that closely resembles that of a different enzyme.

Biochem (Test 2) 52. Many enzymes require cofactors or coenzymes in order to catalyze reactions. Some like the metals copper, zinc, or iron and many vitamins act to speed the enzymatic activity. What do these cofactors and coenzymes contribute to the enzymatic process? Most cofactors and coenzyme modify the active site so that the substrate fits better and many cofactors and coenzymes contribute atoms to the reaction. Cofactors and coenzymes contribute to reactions by breaking hydrogen bonds of the substrate. An induced fit is encouraged by the participation of cofactors and coenzymes and their attachment to an allosteric site. Cofactors and coenzymes inhibit the reaction catalyzed by the enzyme by negative feedback.

Biochem (Test 2) 53. Enyzme structure and the shape of its active site are extremely important for the reaction that the enzyme catalyzes. Which of these choices is a method used to modify the shape of the active site, rendering the enzyme inactive? The product of the reactions binds to the active site on the enzyme causing the active site to be unavailable as a form of noncompetitive inhibition. The product of the reaction bind to an allosteric site on the enzyme causing a change to the shape of the active site as a form of competitive inhibition. The product of the reaction returns to the active site and changes the site as a form of positive feedback, inhibiting further reactions. The product of the reaction binds to an allosteric site on the enzyme causing a change to the shape of the active site as a form o f noncompetitive inhibition. If product binds to allosteric site, NOT active site, it is noncompetitive inhibition.

Biochem (Test 2) 54. A group of students designed an enzyme catalysis experiment. In the experiment, the enzyme, catalase, was used to decompose hydrogen peroxide over a time course. The results are presented below. This data is useful to show the concentration of the product of the catalyzed reaction. This data is useful to show the concentration of the substrate the enzyme decomposed. This data shows the presence of a competitive inhibitor. This data is useful in the determination of the rate of the enzymatic reaction Time (s) 5 10 15 20 25 30 H2O2 decomposed (mL) 2 4 6 8

The increased temperature has caused the enzyme to become denatured. Biochem (Test 2) 55. A further experiment by the same group of students found that a small increase in the temperature of the enzyme catalase and the substrate H2O2 produced a significant increase in the amount of substrate degraded. Which of these possible explanations is the most likely reason for the increased enzymatic activity? The increased temperature has caused the enzyme to become denatured. The increased temperature removed a noncompetitive inhibitor from the enzyme. Evaporation due to the increased temperature increased the concentration of the solutions and as a result increased the reaction rate. The increased temperature caused the enzyme and the substrate to move faster and collide more frequently.