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Flashcards in clinical chemistry Deck (23):
1

how is glucose measured?

not easy to measure glucose itself, so instead measure reduced product (NADPH)

2

glucose + ATP -->

glucose-6-phosphate + ADP
enzyme = hexokinase

3

glucose-6-P + NADP -->

glucono-lactone-6-P + NADPH
enzyme= G6P dehydrogenase

4

when measuring serum enzymes, describe importance of Km

want [substrate] > km

5

describe isozymes

closely related enzymes that catalyze the same reaction but have slightly different aa composition and come from different genes. usually have different charges (helps with electrophoresis) and different kinetics (vmax, Km), some are tissue specific

6

describe the forms of LDH

tetramer, 5 forms Muscle (M) and heart (H) - HHHH, HHHM, HHMM, HMMM, MMMM

7

elevation of which 2 forms of LDH indicate MI

elevation of LDH 1 (HHHH) and LDH2 (HHHM)

8

where, besides the heart, is LDH1 and LDH2 found?

in RBCs, consequence that these levels can be increased with hemolysis

9

which form is high in liver and skeletal mm?

MMMM (LDH5)

10

how is LDH visualized?

redox mechanism that results in conversion of NBT from oxidized (colorless) to reduced (blue) form

11

when does LDH increase after MI?

peaks at about 24 hours

12

3 problems with using LDH for MI detection

-other conditions may also elevate LDH levels
-electrophoresis is labor intensive and slow
-takes 12-24 hrs to appear

13

how is CPK measured?

couple with glucose reaction (common to both reactions is ATP), then measure NADPH

14

what can interfere with CPK measurement?

adenylate kinase- which catalyzes 2 ADP --> ATP and AMP and will thus elevate ATP

15

how can problem with adenylate kinase be avoided?

use a control that is run first without creatinine-P, this will yield the ATP that comes from the adenylate kinase run, then run the reaction with creatinine-P and take the difference

16

isozymes of CPK

dimeric- Muscle (M), brain (B)
MM, MB, BB

17

what increased CPK isozyme indicates MI

MB

18

what are other reasons, aside from MI, that will increase MB?

previously damaged mm and regenerating mm (like that of athletes in training)

19

describe the rise of CPK-MB vs. rise of LDH1/2 after MI

CPK-MB rises faster than LDH1/2

20

preferred enzyme for detecting MI

Troponin (T and I forms)

21

why are TnT and TnI good for detecting MI?

- low serum levels normally
- rise rapidly, can be measured early
- high specificity for cardiac tissue

22

describe RIA process (4)

- attach antibody to polymer
- add sample, remove excess, protein of interest binds Ab
- add second radio labeled ab to protein of interest
- measure radioactivity present

23

describe ELISA process (5)

- attach antibody to polymer
- add sample, remove excess, protein of interest binds Ab
- add second labeled Ab (with enzyme attached) to bind protein
- enzyme takes non-flourescent substrate and makes fluorescent product
- fluorescence is measured