Enfermeria

CLINICAL CHEMISTRY STUDY QUESTIONS
SET THREE

ENZYMES

1. Most methods which involve NAD AND NADH are read at what
wavelength? Why?
NADH absorbs light at 340 nm, NAD does not.

2. What is the effect of a 10 degree rise in temperature on an enzyme reaction?
Rxn rate doubles for every 10( rise.

3. How might the vortexing of an enzyme preparation affect the results? Why?

4.Name three variables which influence enzyme activity.
Time, Temp., pH
5. What are the two types of names given to enzymes.

Systemic – define substrate: rxn catalyzed (end in ase), possibly

coenzyme.
Trivial or recommended name – less lengthy.

6. What is a holoenzyme? apoenzyme? coenzyme?

Holoenzyme – whole protein Apoenzyme – protein portionCoenzyme – non-protein organic substances, loosely coupled.

7. How would the use of dirty glassware affect an enzyme test?

8. How do enzymes affect an chemical reaction?
Lowers energy activation, speeds rxn, not consumed, selective in
use of substrate – specificity

9 Define zero order kinetics for an enzyme reaction.
velocity independent of substrate concentrationSpeed remain constant.
10. Name four types of specificity which enzymes may exhibit.
1. Absolute- only one substrate
2. Group- act only on molecules w/ specific functional group
3. Linkage- act on type of bond
4. Stereochemical- particular isomer.

11. What is the relationship between a katal and IU?
They are units of enzyme activity.
Katal- catalytic amt. Result inconversion of one mole/sec.

IU- amt. Of enzyme that will catalyze the rxn of one micromole

of substrate/ min. under optimal conditions.

12. What are the two basic methods for measuring enzymes?
Endpoint – reactants combine and allowed to proceed for fixed
time. Measure absorbance at end of time. Rxn
usually stopped by changing pH
Kinetic - automation.Multiple measurements detect change in
absorbance.

13. Where is the best place to measure enzymes?
Zero order. Substrate has no effect on rxn. Constant speed.

14. Define Km.
Enzyme affinity for its substrate. Indicates the amt. of substrate
needed for a particular enzymatic rxn.

15. In each of the following diagrams identify the zero order region.

16. What is one advantage ofusing an enzyme as an analytical reagent?
Lowers activation energy and allows for a quick rxn.

17. Name the six classes of enzymes and give an example for each of the first four classes.
76. oxidoreductase – LD
77. transferase- AST, ALT
78. hydrolase- amylase
79. lyase- aldolase
80. isomerase-
81.ligase-

18. In the following hypothetical enzyme test, if you were to plot a vs. time, what would the graph look like?
Zase
Z + NADH --------> A + NAD Absorbance decreases

19.- Which type of inhibitors can be overcome by adding more substrate?

20 What is the name of the graph made by plotting 1/V vs. 1/S?

21 Define zero order kinetics for an enzyme reaction22 Which enzyme would require more substrate to reach V max, one with a low Km or one with a high Km value?

23 An anzyme is able to utilize two substrates .They have different km values. How can you tell which is probably the natural substrate?

24 One the Lineaweaver-Burket Plot, what is the Y intercept? X-intercept?

25 Give the Michaelis-Menton equation.

26. What is the effect ofhemolysis on lipase values?
Hemoglobin inhibits the activity of serum LPS (lipase)
causing false decrease values.

27 . What effect would morphine or codeine have on amylase values?
Increases values of amylase conc.

28. A technologist runs an amylase assay on a lipemic specimen and it is normal. The doctor insists that the patient has pancreatitis. Explain the results. What...