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Enzymes - exercise - Vladimíra Kvasnicová
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Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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Page 1: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Enzymes- exercise -

Vladimíra Kvasnicová

Page 2: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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 statement N = I disagree with the statement

? = I don't know

No a b c d

1 Y N ? Y N ? Y N ? Y N ?

2 Y N ? Y N ? Y N ? Y N ?

3 Y N ? Y N ? Y N ? Y N ?

4 Y N ? Y N ? Y N ? Y N ?

5 Y N ? Y N ? Y N ? Y N ?

Page 3: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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 statement N = I disagree with the statement

? = I don't know

No a b c d

1 Y N ? Y N ? Y N ? Y N ?

2 Y N ? Y N ? Y N ? Y N ?

3 Y N ? Y N ? Y N ? Y N ?

4 Y N ? Y N ? Y N ? Y N ?

5 Y N ? Y N ? Y N ? Y N ?

Page 4: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Phosphatase catalyzes

a) insertion of Pi into a substrate

b) removing of Pi from a substrate

c) hydrolysis of an ester bond

d) reaction producing ATP

Page 5: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Phosphatase catalyzes

a) insertion of Pi into a substrate

b) removing of Pi from a substrate

c) hydrolysis of an ester bond

d) reaction producing ATP

No a b c d

1 Y N ? Y N ? Y N ? Y N ?

Page 6: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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)

Page 7: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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

Page 8: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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

Page 9: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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)

Page 10: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Carboxylase elongates a molecule by 1 carbon (as carboxyl, COO-). It needs CO2 disolved in water = HCO3

-.

It is a ligase – it needs energy for its function: ATP is cleaved to ADP and phosphate.

Page 11: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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)

Page 12: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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 O2)is reduced to H2O

Page 13: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Alanin aminotransferase (ALT) catalyzes a reaction of Ala with -ketoglutarate. The reaction produces

a) oxaloacetate

b) aspartate

c) glutamate

d) pyruvate

Page 14: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Alanin aminotransferase (ALT) catalyzes a reaction of Ala with-ketoglutarate. The reaction produces

a) oxaloacetate

b) aspartate

c) glutamate

d) pyruvate

Page 15: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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 –NH2 group from alanine to -ketoglutarate(alanine is converted to pyruvate, -ketoglutarate gives glutamate)

- reversible reaction -

Page 16: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Enzyme catalyzing cleavage of a bond between 2 amino acids in

proteins belongs among

a) lyases

b) peptidases

c) hydrolases

d) transferases

Page 17: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Enzyme catalyzing cleavage of a bond between 2 amino acids in

proteins belongs among

a) lyases

b) peptidases

c) hydrolases

d) transferases

Page 18: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

The figure is found at http://www.richmond.edu/~jbell2/04F03.JPG (Jan 2007)

H2O

AA1 AA2

dipeptide

peptide bond

Page 19: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose a corret statement(s):

a) maximal velocity Vmax is related to maximal number of substrate molecules transformed by the enzyme per unit of time

b) KM is expressed in velocity units (mol.s-1)

c) KM = concentration of a substrate needed to reach ½ Vmax of the reaction

d) KM = concentration of a substrate needed for transformation of ½ enzyme molecules to complex enzyme-substrate

Page 20: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose a corret statement(s):

a) maximal velocity Vmax is related to maximal number of substrate molecules transformed by the enzyme per unit of time

b) KM is expressed in velocity units (mol.s-1)

c) KM = concentration of a substrate needed to reach ½ Vmax of the reaction

d) KM = concentration of a substrate needed for transformation of ½ enzyme molecules to complex enzyme-substrate

Page 21: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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

Page 22: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

KM 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

Page 23: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

KM 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

Page 24: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

The figure is found at http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/EnzymeKinetics.html (Dec 2006)

Summary of an enzyme inhibition

Page 25: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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

Km describes affinity of an enzymeto its substrate

! indirect proportionality !

Page 26: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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 Vmax

Page 27: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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 Vmax

Page 28: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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)

Inhibition of enzymes

Page 29: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Competitive inhibition

• inhibitor resembles substrate

• it is bound to an active site but not converted by the enzyme

• increases Km (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)

Page 30: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

• inhibitor binds at a site other than the substrate-binding site

• inhibition is not reversed by increasing concentration of substrate(no Km change)

• Vmax 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)

Noncompetitive inhibition

Page 31: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme1

Page 32: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme2

Page 33: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme3

Page 34: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme4

Page 35: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme1

Page 36: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme2

Page 37: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme3

Page 38: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

Choose the proper graph describing

a) competitive inhibition

b) noncompetitive inhibition

c) inhibition by substrate excess

d) allosteric enzyme4

Page 39: Enzymes - exercise - Vladimíra Kvasnicová. Each question of the test contains 4 statements (a, b, c, d). You can obtain 1 point (correct answer), –1 point.

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