Enzyme Properties and Kinetics - Exam Questions

Question 1

The active site of an enzyme…

Answer 1

…is complementary to the transition state

Question 2

Give an example of an oxidoreductase.

Answer 2

Lactate dehydrogenase

Question 3

What do lyases catalyse?

Answer 3

The cleavage of C-C, C-O or C-N bonds

Question 4

What is the fastest rate of enzyme-catalysed reactions in the human body?

Answer 4

50oC

Question 5

What is the optimal pH of enzyme catalysed reaction in the human body?

Answer 5

Varies for each enzyme

Question 6

Cu2+ is a co factor for:

a. trypsin
b. chymotrypsin
c. urease
d. glutathione peroxidase
e. cytochrome oxidase

Answer 6

e. Cu2+ is a cofactor for cytochrome oxidase

Question 7

What is Fe2+/Fe3+ a co factor for?

Answer 7

Cytochrome oxidase

Question 8

K+ is a co-factor for.?

Answer 8

Pyruvate kinase

Question 9

Mg2+ is a cofactor for?

Answer 9

pyruvate kinase

Question 10

Ni2+ is a cofactor for..?

Answer 10

urease

Question 11

Se is a cofactor for..?

Answer 11

Glutathione peroxidase

Question 12

Zn2+ is a cofactor for..?

Answer 12

Carbonic anhydrase

Question 13

What are isoenzymes?

Answer 13

Different proteins that catalyse the same reaction.

Question 14

What is the Michaelis-Menten equation?

Answer 14

V0=Vmax[S]/(Km+[S])

Question 15

Km is…

Answer 15

Km = [S] when V0=0.5Vmax

Question 16

Km = k2+k-1/k1. Km represents the affinity of enzyme for its substrate…

Answer 16

…when k2 becomes negligible

Question 17

What is Kcat?

Answer 17

The number of product molecules produced by one active site of an enzyme per unit time

Question 18

The catalytic efficient of enzymes is best compares by..?

Answer 18

Kcat/Km

Question 19

The Lineweaver - Burker plo…

Answer 19

…uses the inverse of the Michaelis-Menten equation

Question 20

Where is 1/Vmax found on the Lineweaver-Burke plot?

Answer 20

At the interception of the Y-axis

Question 21

When will the enzymes ALT, troponin-t and CK be significatly raise in the blood.

Answer 21

Because they have escaped damaged tissues.

Question 22

Where is lactate dehydrogenase found?

Answer 22

Exists as a tetramer of heart or muscle subunits

Question 23

What do competitive inhibitors do to the Km?

Answer 23

Increases the Km

Question 24

Non competitive inhibitors…?

Answer 24

Lower the Vmax

Question 25

How can acetylcholinesterase by inhibited?

Answer 25

Can be inhibited reversibly by neostigmine

Question 26

Enzyme kinetics show a sigmoid curve when regulated…

a. by phosphorylation
b. be induction or repression of enzyme synthsis
c. allosterically
d. by adenylation
e. by ADP-ribosylation

Answer 26

c. Enzymes kinetics show a sigmoidal curve when regulated allosterically.

Question 27

Phosphorylation of enzymes:

Answer 27

Often adds a phosphate group to a serine residue

Question 28

ADP-ribosylation function..

Answer 28

..requires NAD as a reactant

Question 29

What is allosteric control of an enzyme typically effected by?

Answer 29

End-product inhibition