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The activation energy is the difference between the energy of the reactants and the tip of the hump on the diagra

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The activation energy is the difference between the energy of the reactants and the tip of the hump on the diagra

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    2. How Enzymes Work

    14. Feedback Inhibition:The product forms shuts down the process by binding the enzyme at an allosteric site!

    26. Multiple Choice Question: E1 E2 E3 W X Y Z 1. In the series of enzyme reactions shown above, product Z is able to occupy the active site of enzyme E2. Product Z can therefore first inhibit the production of (A) W (B) E1 (C) X (D) E2 (E) Y

    27. Multiple Choice Question: 2. A substrate molecule may be bound to the active site of an enzyme by all of the following EXCEPT (A) hydrogen bonds (B) peptide bonds (C) ionic bonds (D) van der Waals interactions (E) hydrophobic interactions

    28. For the next 3 questions:

    29. Multiple Choice Question: 3. In an experiment to test the effect of amylase on starch, the control would be (A) flask A only (B) flask B only (C) flask C only (D) flasks A and B (E) flasks A and C

    30. Multiple Choice Question: 4. After 2 minutes, a positive test for sugar would most likely be observed in (A) flask A only (B) flask B only (C) flask C only (D) flask A and C (E) flask B and C

    31. Multiple Choice Question: 5. Support for the hypothesis of enzyme denaturation can be obtained by comparing starch digestion in (A) flasks A and B after 5 minutes (B) flasks B and C after 5 minutes (C) flasks A and C after 5 minutes (D) flask A at time zero and again after 5 minutes (E) flask B at time zero and again after 5 minutes

    32. Multiple Choice Question: Questions 6 - 8 In a laboratory experiment using spectrophotometry, an enzyme is combined with its substrate at time zero. The absorbance of the resulting solution is measured at time zero and at five-minute intervals. In this procedure an increase in absorbance is related to the amount of product formed during the reaction. The experiment is conducted using the three preparations shown in the table below. Absorbance Enzyme Preparation 0 min 5 min 10 min 15 min 20 min I. 3 mL of enzyme preparation 0.0 .22 .33 .38 .37 3 mL of substrate pH 5.0 II. 3 mL of boiled enzyme preparation 0.0 .06 .04 .03 .04 2 mL of substrate pH 5.0 III.3 mL of enzyme preparation 0.0 .32 .37 .36 .38 2 mL of substrate pH 6.0

    33. Multiple Choice Question: 6. The most likely reason for the failure of the absorbance to increase significantly after 10 minutes in preparation III is that (A) the reaction is thermodynamically impossible at pH 6.0 (B) the enzyme is not active at this pH (C) a pH of 6.0 prevents color development beyond an absorbance of .38 (D) the enzyme is degraded more rapidly at pH 6.0 than it is at pH 5.0 (E) most of the substrate was digested during the first 10 minutes

    34. Multiple Choice Question: 7. Which of the following statements is best supported by the data? (A) Increasing the pH to 7.0 would yield an absorbance higher than 0.30 after 5 minutes. (B) The enzyme demonstrates more activity at pH 6.0 than at pH 5.0. (C) The enzyme has no activity at pH 6.0. (D) A pH of 5.0 is the optimum for the activity of the enzyme. (E) The enzymatic activity is independent of pH.

    35. Multiple Choice Question: 8. Which of the following can best be concluded from a comparison of the results of preparation II with those of preparation I? (A) Heating the enzyme is not required to increase the absorbance. (B) Boiling does not break down the substrate. (C) Most of the increase in the amount of product in preparation I was due to an enzymatic degradation of the substrate. (D) Enzymatic reactions proceed at a faster rate after boiling the enzyme. (E) Products resulting from the breakdown of the enzyme are responsible for the absorbance increase in preparation II.

    36. Multiple Choice Question: 9. Which of the following can be used to determine the rate of enzyme-catalyzed reactions? (A) Rate of disappearance of the enzyme (B) Rate of disappearance of the substrate (C) Rate of disappearance of the product (D) Change in volume of the solution (E) Increase of activation energy

    37. Multiple Choice Question: 10. Within the cell, many chemical reactions that, by themselves, require energy input (have a positive free-energy change) can occur because the reactions (A) may be coupled to the hydrolysis of ATP (B) take place very slowly (C) take place when the cells are at unusually high temperatures (D) are catalyzed by enzymes (E) are aided by various metal ions that act as catalysts

    38. For the next 4 questions: Refer to the following graph. The solid curve and the dashed curve represent alternate pathways for the same reaction. One pathway is enzyme catalyzed.

    39. Multiple Choice Question: 11. Represent the activation energy of the enzyme- catalyzed reaction

    40. Multiple Choice Question: 12. Represents the net energy change of the reaction

    41. Multiple Choice Question: 13. Represent the energy state of the products of the enzyme-catalyzed pathway

    42. Multiple Choice Question: 14. Represents the energy state of the products of the pathway that is not enzyme-catalyzed

    43. FR Questions… 1994: Enzymes are biological catalysts. Relate the chemical structure of an enzyme to its specificity and catalytic activity.

    44. FR Questions… 1994: Enzymes are biological catalysts. Relate the chemical structure of an enzyme to its specificity and catalytic activity.

    45. FR Questions… 1994: Enzymes are biological catalysts. b. Design a quantitative experiment to investigate the influence of pH or temperature on the activity of an enzyme.

    46. FR Questions… 1994: Enzymes are biological catalysts. b. Design a quantitative experiment to investigate the influence of pH or temperature on the activity of an enzyme.

    47. FR Questions… 1994: Enzymes are biological catalysts. c. Describe what information concerning the structure of an enzyme could be inferred from your experiment.

    48. FR Questions… 1994: Enzymes are biological catalysts. c. Describe what information concerning the structure of an enzyme could be inferred from your experiment.

    49. FR Questions… 1988: After an enzyme is mixed with its substrate, the amount of product formed is determined at 10-second intervals for 1 minute. Data from this experiment are shown below:

    50. Graph of the data:

    51. FR Questions… a. What is the initial rate of this enzymatic reaction? b. What is the rate after 50 seconds? Why is it different from the initial rate?

    52. FR Questions… c. What would be the effect on product formation if the enzyme were heated to a temperature of 100 oC for 10 minutes before repeating the experiment? Why?

    53. FR Questions… d. How might altering the substrate concentration affect the rate of the reaction? Why?

    54. FR Questions… e. How might altering the pH affect the rate of reaction? Why?

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