Exam 3 enzymes

Question 1

Plasma/serum enzyme concentration levels are useful in

Answer 1

diagnosis in disease or physiologic abnormalities

Question 2

Isoenzyme

Answer 2

particular enzyme may exist in multiple forms in varying quaternary structures.

Question 3

Isoenzymes are differentiated based on

Answer 3

Electrophoretic mobility, solubility, or resistance to inactivation.

Question 4

Isoform

Answer 4

Enzyme is subject to post-translational modifications.

Question 5

___ and ____ contribute to heterogeneity in properties and functions.

Answer 5

Isoenzyme and Isoforms

Question 6

Proenzyme (zymogen)

Answer 6

secreted in inactive form (mostly digestive enzymes)

Question 7

Inorganic co factors are composed of

Answer 7

Metal Ions as activators (Cl-, Mg+, Cu-)

Question 8

Organic cofactors include

Answer 8

Coenzymes: NAD; ATP; ADP
Prosthetic group: coenzyme bound tightly to the enzyme
Holoenzyme: complete and active system
Apoenzyme: (enzyme portion + coenzyme)

Question 9

Michaelis and Menten Theory

Answer 9

Substrate readily binds to free enzyme at a low substrate concentration. Reaction rate (velocity) steadily increases when more substrate is added. With the amount of enzyme exceeding the amount of substrate.

Question 10

Michaelis- menten constant

Answer 10

Km= [S] 1/2 max, indicates the amount of substrate needed for a particular enzymatic reaction.

Question 11

In the michaelis-menten constant, if [S] is greater than Km by factor of 100

Answer 11

Follow zero order kinetics

Question 12

If more than one substrate

Answer 12

Lowest Km is a natural substrate (not man made)

Question 13

Lineweaver-burk plot

Answer 13

is a double reciprocal of Michaelis-Menten- yields a straight line.
Most accurate and convenient to determine Vmax and Km.
Reciprocal is taken of both substrate concentration and velocity of enzymatic reaction.
Can be used to identify the type of inhibitor.

Question 14

Optimal pH for enzymes

Answer 14

7.0-8.0, may denature an enzyme or influence in ionic state if >,<

Question 15

Common activators:

Answer 15

Calcium, iron, magnesium, manganese, zinc, and potassium.
Nonmetallic: bromide and chloride.
If there is excess, it may inhibit reaction.

Question 16

Coenzymes (organic)

Answer 16

Nucleotide phosphate and vitamins.
When quantitating an enzyme that requires coenzymes, always provide excess to avoid dependency.

Question 17

When measuring enzyme activity:

Answer 17

No inhibitors.
Control variables.
Use coupled reactions.
Colorimetric.
UV involving NAD and NADH (340 nm)
Measured at zero order region.

Question 18

Measurement of Enzyme Mass

Answer 18

Quantify enzyme concentration by mass.
CK-MB.
Can overestimate due to cross-reactivity with inactive enzymes, macroenzymes, zymogens or partially digested enzymes.
Can also be quantified by electrophoretic techniques- isoenzymes/isoforms