1. Enzymes - exercise - Vladimíra Kvasnicová

2. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point (incorrect answer) or 0 point (if ? is marked). All four statements can be either correct or incorrect or some of the statements can be correct and some incorrect. Use the following schema to complete the answer table: Y = I agree with the statementN = I disagree with the statement ? = I don't know NoNo abcd 1YN?YN?YN?YN? 2YN?YN?YN?YN? 3YN?YN?YN?YN? 4YN?YN?YN?YN? 5YN?YN?YN?YN?

3. NoNo abcd 1YN?YN?YN?YN? 2YN?YN?YN?YN? 3YN?YN?YN?YN? 4YN?YN?YN?YN? 5YN?YN?YN?YN?

4. Phosphatase catalyzes a) insertion of P i into a substrate b) removing of P i from a substrate c) hydrolysis of an ester bond d) reaction producing ATP

5. Phosphatase catalyzes a) insertion of P i into a substrate b) removing of P i from a substrate c) hydrolysis of an ester bond d) reaction producing ATP NoNo abcd 1YN?YN?YN?YN?

6. The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley ‑ Liss, Inc., New York, 1997. ISBN 0 ‑ 471 ‑ 15451 ‑ 2 dephosphorylation phosphorylation (hydrolytic cleavage of an ester bond) (isertion of phosphate to a substrate) hydrolase phosphotransferase (esterase)

7. Choose correct statements: a)dehydrogenases catalyze oxidative- reducing reactions b)carboxylases need ATP for their function c)kinases transfer a phosphate from an energy rich compound to a substrate d)hydroxylases catalyze oxidation of a substrate

8. Choose correct statements: a)dehydrogenases catalyze oxidative- reducing reactions b)carboxylases need ATP for their function c)kinases transfer a phosphate from an energy rich compound to a substrate d)hydroxylases catalyze oxidation of a substrate

9. The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley ‑ Liss, Inc., New York, 1997. ISBN 0 ‑ 471 ‑ 15451 ‑ 2 Alcohol dehydrogenase oxidation of a substrate without direct presence of oxygen (NAD + used as a coenzyme)

10. Carboxylase elongates a molecule by 1 carbon (as carboxyl, COO - ). It needs CO 2 disolved in water = HCO 3 -. It is a ligase – it needs energy for its function: ATP is cleaved to ADP and phosphate.

11. The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley ‑ Liss, Inc., New York, 1997. ISBN 0 ‑ 471 ‑ 15451 ‑ 2 Reaction catalyzed by glucokinase (or hexokinase)

12. The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley ‑ Liss, Inc., New York, 1997. ISBN 0 ‑ 471 ‑ 15451 ‑ 2 Hydroxylase = monoxygenase catalyzes an introduction of 1 oxygen atom to a substrate as –OH; the second oxygen (from molecular O 2 ) is reduced to H 2 O

13. Alanin aminotransferase (ALT) catalyzes a reaction of Ala with  - ketoglutarate. The reaction produces a) oxaloacetate b) aspartate c) glutamate d) pyruvate

14. Alanin aminotransferase (ALT) catalyzes a reaction of Ala with  -ketoglutarate. The reaction produces a) oxaloacetate b) aspartate c) glutamate d) pyruvate

15. The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley ‑ Liss, Inc., New York, 1997. ISBN 0 ‑ 471 ‑ 15451 ‑ 2 Alanine aminotransferase transfers –NH 2 group from alanine to  -ketoglutarate (alanine is converted to pyruvate,  -ketoglutarate gives glutamate) - reversible reaction -

16. Enzyme catalyzing cleavage of a bond between 2 amino acids in proteins belongs among a) lyases b) peptidases c) hydrolases d) transferases

17. Enzyme catalyzing cleavage of a bond between 2 amino acids in proteins belongs among a) lyases b) peptidases c) hydrolases d) transferases

18. The figure is found at http://www.richmond.edu/~jbell2/04F03.JPG (Jan 2007)http://www.richmond.edu/~jbell2/04F03.JPG H2OH2O AA 1 AA 2 dipeptide peptide bond

19. Choose a corret statement(s): a)maximal velocity V max is related to maximal number of substrate molecules transformed by the enzyme per unit of time b)K M is expressed in velocity units (mol.s -1 ) c)K M = concentration of a substrate needed to reach ½ V max of the reaction d)K M = concentration of a substrate needed for transformation of ½ enzyme molecules to complex enzyme-substrate

20. Choose a corret statement(s): a)maximal velocity V max is related to maximal number of substrate molecules transformed by the enzyme per unit of time b)K M is expressed in velocity units (mol.s -1 ) c)K M = concentration of a substrate needed to reach ½ V max of the reaction d)K M = concentration of a substrate needed for transformation of ½ enzyme molecules to complex enzyme-substrate

21. The figure is found at http://fig.cox.miami.edu/~cmallery/255/255enz/gk3x15.gif (Dec 2006)http://fig.cox.miami.edu/~cmallery/255/255enz/gk3x15.gif

22. K M of a pair enzyme-substrate a)is decreased by a competitive inhibitor b)is equal to the concentration of a substrate when an activity of the enzyme is maximal c)is increased by a noncompetitive inhibitor d)is directly proportional to an affinity of the enzyme to its substrate

23. K M of a pair enzyme-substrate a)is decreased by a competitive inhibitor b)is equal to the concentration of a substrate when an activity of the enzyme is maximal c)is increased by a noncompetitive inhibitor d)is directly proportional to an affinity of the enzyme to its substrate

24. The figure is found at http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/EnzymeKinetics.html (Dec 2006) http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/EnzymeKinetics.html Summary of an enzyme inhibition

25. The figure is found at http://fig.cox.miami.edu/~cmallery/255/255enz/gk3x15.gif (Dec 2006) http://fig.cox.miami.edu/~cmallery/255/255enz/gk3x15.gif K m describes affinity of an enzyme to its substrate ! indirect proportionality !

26. Choose a correct statement(s): a)an inhibition is competitive if an inhibitor competes with a substrate to be bound into an active site of an enzyme b)a noncompetitive inhibition can be decreased by an increasing of a substrate concentration c)competitive inhibitors have very often a similar structure as a substrate d)noncompetitive inhibitors decrease V max

27. Choose a correct statement(s): a)an inhibition is competitive if an inhibitor competes with a substrate to be bound into an active site of an enzyme b)a noncompetitive inhibition can be decreased by an increasing of a substrate concentration c)competitive inhibitors have very often a similar structure as a substrate d)noncompetitive inhibitors decrease V max

28. The figure is found at http://stallion.abac.peachnet.edu/sm/kmccrae/BIOL2050/Ch1-13/JpegArt1- 13/05jpeg/05_jpeg_HTML/index.htm (Dec 2006) http://stallion.abac.peachnet.edu/sm/kmccrae/BIOL2050/Ch1-13/JpegArt1- 13/05jpeg/05_jpeg_HTML/index.htm Inhibition of enzymes

29. Competitive inhibition inhibitor resembles substrate it is bound to an active site but not converted by the enzyme increases K m (  affinity of enzyme to its S) if concentration of a substrate is increased the inhibition is decreased the inhibition is reversible The figure is found at: http://www.steve.gb.com/science/enzymes.html (December 2006)http://www.steve.gb.com/science/enzymes.html

30. inhibitor binds at a site other than the substrate-binding site inhibition is not reversed by increasing concentration of substrate (no K m change) V max is decreased (it is related to decreasing of active enzyme concentration) reversible only if the inhibitor is not bound by covalent bond The figure is found at: http://www.steve.gb.com/science/enzymes.html (December 2006)http://www.steve.gb.com/science/enzymes.html Noncompetitive inhibition

31. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 1

32. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 2

33. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 3

34. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 4

35. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 1

36. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 2

37. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 3

38. Choose the proper graph describing a)competitive inhibition b)noncompetitive inhibition c)inhibition by substrate excess d)allosteric enzyme 4

39. The figure is adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley ‑ Liss, Inc., New York, 1997. ISBN 0 ‑ 471 ‑ 15451 ‑ 2 Allosteric enzyme: a) monomeric, b) oligomeric