20090204-clinical Enzymology Questions And Answers Final For Website 602f31

Clinical Enzymology Questions 1. For a biological process to occur a free energy of activation must be overcome. Enzymes work in this process to: a. b. c. d.

Lower the free energy of activation Raise the free energy of activation Enzymes have no effect on free energy of activation The effect on free energy of activation is dependent on the enzyme in question e. None of the above 2. CK-M and CK-B are examples of what type of enzyme? a. b. c. d. e.

Homogeneous enzymes Isoenzymes Heterogeneous enzymes Co-factors None of the above

3. A 68-year-old male presents to the emergency room with acute mental confusion. Upon questioning his family they recall that for the last several months he has been complaining of tingling and loss of feeling in his hands and feet, difficulty walking, and vomiting. Which of the following co-factors is he most likely suffering from a deficiency in? a. b. c. d. e.

Folic Acid coenzymes Biotin Flavin coenzymes Thiamine pyrophosphate B12 coenzymes

4. Which of the following type of enzyme reaction does not normally require the use of a cofactor? a. b. c. d.

Oxidation-reduction reaction Group Transfer reactions Isomerizations Hydrolytic reactions

e. Reactions that form covalent bonds 5. Factors that influence the plasma level of enzymes include which of the following: a. b. c. d. e. f.

The amount of tissue that is injured The relative concentration of the enzyme within the cell The type of cell injury (acute or chronic) The size of the enzyme in question All of the above None of the above

6. An enzyme reaction will occur at a constant rate until a saturation point is reached. What is the explanation for the existence of a saturation point? a. b. c. d. e.

Each enzyme only has a set number of binding sites Enzymes can only react at a certain speed Enzyme binding occurs at a set speed All of the above None of the above

7. The following graph is an example of what type of inhibition?

a. Simple noncompetitive inhibition b. Mixed noncompetitive inhibition c. Competitive inhibition

d. Uncompetitive inhibition e. None of the above 8. Enzyme activity is measured in international units (IU). Specific to enzymes define an IU: a. The amount of enzyme needed to catalyze 1 mole of product b. The amount of enzyme needed to catalyze 1 micromole of product c. The amount of enzyme needed to catalyze 1 micromole of product in 1 minute d. The amount of enzyme needed to catalyze 1 mole of product in 1 minute e. The amount of enzyme needed to catalyze 1 mole of product in 1 second 9. A physician’s office calls the pathology lab at 9pm on a Friday

inquiring about a patient’s lab results, which are significantly different from the previous results with no change in the patient’s condition. After ing that the collection and specimen processing were done correctly, what is the most logical explanation for the discrepancy. (Assume that both lab results are correct, but the patient is not suffering from an enzyme problem) a. The results are from different laboratories and they use a different standard of measurement. b. The laboratory machines where recently serviced, thus making the second test void. c. There was an error in the computer program that relays the results to the physician’s office changing the second lab value. d. The patient blood was switched with another patient and the second value is not the patients. e. None of the above 10.A patient with prostate cancer is being treated with androgen blockers. Which of the following enzymes would be the best to monitor for recurrence of disease? a. PSA b. Acid Phosphatase

c. Alkaline Phosphatase d. Estrogen e. Testosterone

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Clinical Enzymology Answers 1. Answer: A. The free energy of activation is the energy required by a biological process before a chemical reaction can occur. Enzymes all work to lower the free energy of activation and thus causing a chemical reaction to occur more rapidly. (Henry’s pg 246). 2. Answer: B. Isoenzymes are structurally different forms of the same enzyme that catalyze the same type of reaction in different parts of the body. Knowing this fact can be useful in determining which part of the body has dying tissue as the specific isoenzyme will be elevated. Other examples include Lactate dehydrogenase which has both a heart and muscle form. (Henry’s pgs 246-247). 3. Answer: D. The patient is suffering from beriberi which is due to a deficiency of Thiamine coenzymes and/or Vitamin B1 deficiency. Symptoms include vomiting, loss of sensation in hands and feet, tingling and hands and feet, coma, death, mental confusion, nystagmus, and speech difficulties. (Henry’s pg 247, table 20-3). 4. Answer: D. Hydrolytic reactions do not generally require the use of enzyme cofactors in their reactions. All of the other four types of reactions generally do require the use of an enzyme cofactor to catalyze the reaction. (Henry’s pg 247). 5. Answer: E. The relative concentration in plasma of enzymes is dependent on a number of factors including the type of cell injury, the extent of cell injury, the size of the enzyme, the location of the enzyme within the cell, and the relative concentration of the enzyme within the cell. (Henry’s pg 248). 6. Answer: A. Enzymes exhibit saturation, that is to say there is a point where no matter how much substrate you add the reaction cannot occur at a faster rate. The physical explanation for this is that binding of the substrate reduces the number of binding sites available for additional substrate to bind. Eventually the binding sites will all be filled and no additional substrate can bind to the enzyme thus saturating the reaction. (Henry’s pg 248, pg 249, Figure 20-4).

7. Answer: C. Competitive inhibition occurs when an inhibitory substrate binds to the same binding site as an enzyme. All of the lines intersect at the 0 point demonstrating that in an infinite concentration of the substrate there is no inhibition as the enzyme will always have something to bind to and create the reaction. (Henry’s pg 250-251, table 20-8, Quick Compendium pg 2-3). 8. Answer: C. The international unit for measuring enzyme activity is defined as the amount of enzyme needed to catalyze the formation of 1 micromole of product in 1 minute. Choice E defines a katal (kat) which is the SI unit of measurement for enzyme activity and is equal to 6x10^7 IU. (Henry’s pg 253, Quick Compendium pg 3). 9. Answer: A. Although laboratories may measure their lab tests in the same units, either IU or kal, the conditions between laboratories that run the assays are not identical and therefore the results may seem to be contradictory, but they actually may have a different normal range. Most labs will print their normal ranges along with the patient’s results to stop confusion between laboratories. (Henry’s pg 253). 10. Answer: B. Acid Phosphatase have largely been replaced by PSA for the detection and monitoring of prostate cancer, however in cases where androgen deprivation therapy is used, PSA activity is also decreased, but Acid Phosphatase is unaffected. (Henry’s pg 255).