20-XC Enzymes Due right at the end of lecture 1. Enzymes belong to which class of organic compounds? a. Carbohydrates b. Esters c. Lipids d. proteins 2. Kinases belong to which class of enzymes? a. Isomerases b. Transferases c. Ligases d. hydrolases 3. Match the type of reaction with an enzyme. 1) aminase 2) dehydrogenase 3) isomerase 4) synthetase A. Converts a cis-fatty acid to a trans-fatty acid. B. Removes 2 H atoms to form a double bond. C. Combines two molecules to make a new compound. D. Adds NH3. 4. What class of enzymes catalyzes each of the following? a. the transfer of an amino group b. the removal of hydrogen from lactate 5. What is the class of the enzyme lipase that catalyzes the hydrolysis of ester bonds in triglycerides?

6. The compound that has a reaction catalyzed by an enzyme is called a(n): a. Activator b. Coenzyme c. Cofactor d. substrate 7. A patient arrives in the emergency room complaining of chest pains. All of the following enzymes would be tested for in the blood serum except: a. lactate dehydrogenase b. creatine kinase c. aspartate transaminase d. alkaline phosphatase 8. What is the function of the active site in an enzyme? 9. The optimum temperature for most enzymes operating in the human body is: a. 273 K b. 37 °C c. 98.6 °C d. 120 °C 10. Trypsin, a peptidase that hydrolyzes polypeptides, functions in the small intestine at an optimum pH of 8. All of the following would decrease rates of a trypsin catalyzed reaction except: a. lowering the concentration of polypeptides b. adding more trypsin c. changing the pH to 3 d. running the reaction at 75ºC 11. Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction. 1) no change 2) increase 3) decrease A. Increasing the concentration of sucrose B. Changing the pH to 4 C. Running the reaction at 70°C

12. Describe what effect the following changes would have on the rate of the reaction catalyzed by urease: a. increasing the urea concentration b. lowering the temperature to 10 ˚C 13. Identify each description as an inhibitor that is: 1) Competitive 2) Noncompetitive A. Increasing substrate reverses inhibition. B. Binds to enzyme surface, but not to the active site. C. Structure is similar to substrate. D. Inhibition is not reversed by adding more substrate. 14. Identify each statement as: zymogen (Z) allosteric enzyme (A) positive regulator (PR) feedback control (FC) 1. An enzyme in a pathway that controls the rate of the reaction. 2. Speeds up a reaction by combining with an enzyme in the pathway. 3. Removal of a peptide activates the enzyme. 4. Some product binds to the first enzyme to limit the synthesis of product. 15. How is the rate of a reaction sequence regulated in feedback control? 16. Why is pepsin, a digestive enzyme, produced as the zymogen pepsinogen?

17. The deficient vitamin in the condition called rickets is: vitamin C or ascorbic acid b. vitamin B3 or niacin c. vitamin B12 or cobalamin d. vitamin D or cholecalciferol 18. Identify each compound as a water-soluble vitamin (W)or fat-soluble vitamin (F): 1. Folic acid (vitamin B9) 2. Retinol (Vitamin A) 3. Vitamin C 4. Vitamin E 5. Niacin (vitamin B3) 19. Identify the vitamin associated with each 1. Thiamin (B1) 2) Vitamin A 3) Vitamin K 4) Vitamin D 5) Vitamin C (Ascorbic Acid) A. Collagen formation B. Beriberi C. Absorption of phosphorus and calcium in bone D. Vision E. Blood clotting 20. All of the enzymes described in each of the following statements require a cofactor except: a. needs Zn2+ for catalytic activity b. an enzyme that consists of a quaternary structure attached to vitamin B6 c. its active form consists of two polypeptide chains d. requires vitamin B1 (thiamine) 21. Indicate whether each of the following is active as a simple enzyme or requires a cofactor: a. a polypeptide that needs Mg2+ for catalytic activity b. an active enzyme composed only of a polypeptide chain c. an enzyme that consists of a quaternary structure attached to vitamin B6 22. Why do you need a certain amount of thiamine and riboflavin in your diet every day but not vitamin A or D?