Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry II > Chapter 67: Enzyme Diagnostics > Flashcards

Chapter 67: Enzyme Diagnostics Flashcards

1
Q

Enzyme leakage into the plasma may result from

A
  • Cellular necrosis
  • Membrane damage due to ischemia
  • Increased cellular turnover (normal active growth or malignant disease)
  • Induction of intracellular enzymes which increases the concentration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Enzyme activity is measured as

A
  • Substrate converted per unit time

- Optimal conditions of [S], Temp, pH, [cofactors]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Advantages of UV light absorption

A
  • Reduced NAD or NADP to absorb UV light at 340 nm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

If the reactions do not use NAD or NADP - coupled reactions

A
  • Particular tissues involved cannot usually be pinpointed

- Except Alcohol DH (liver) & Acid Phosphatase (prostate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Isoenzyme assay allows

A
  • Differential diagnosis

- They can be separated and quantified

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The absorption spectra of niacin and flavin coenzymes

A
  • Follows rate of reduction of NAD (increase in absorption at 340nm)
  • Follow rate of reduction of FAD (fall in absorbance at 450nm)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Alkaline phosphates (ALP)

A
  • Membrane bound isoenzymes

- Activity varies with both age and sex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Assay of plasma ALP activity is useful for

A
  • Assessing hepatobiliary and bone diseases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Hepatic disease (ALP)

A
  • Obstructed bile flow (cholestasis, pancreatic cancer) = 10x increase in plasma ALP
  • Viral hepatitis = 2x increase in plasma ALP
  • ALP only increases in small amounts following hepatocellular damage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Bone disease (ALP)

A
  • Paget’s disease of bone remodelling affecting the femur and hip of elderly men
  • Pagest’s = plasma ALP increases 25x
  • Ricketts = ALP increases 2-4x
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Separation of liver and bone ALP isoenzymes by

A
  • Electrophoresis at pH 8.6
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Gamma glutamyl transferase

A
  • Membrane bound enzyme
  • High concentrations in liver and kidney
  • Production is enhanced by drugs and alcohol
  • Used to confirm hepatic origin for ALP elevation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Elevated levels of GGT

A
  • (Often more than 10x) indicate cholestasis and cirrhosis
  • More sensitive than AP and more liver specific
  • Reyes syndrome, MI and acute pancreatitis as well
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Some pathological causes of high GGT include

A
  • Hepatitis (often 5x)

- Alcohol abuse (usually less than 5x)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Aspartate transaminase (AST)

A
  • Glutamic oxaloacetic transaminase (GOT)
  • Present in most tissues (primarily skeletal and cardiac muscle, liver and kidney)
  • Mitochondrial and cytoplasmic isoenzymes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In alcoholic liver disease levels of AST

A
  • AST > ALT
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Assay of plasma AST (activity coupled to MDH) measures

A
  • Myocardial infarction
  • Acute liver damage
  • Muscular dystrophy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Alanine transaminase (ALT)

A
  • Glutamic pyruvic transaminase (GPT): cytoplasmic enzyme
  • Generally lower concentrations than AST in tissues
  • In the liver the activity of ALT and AST are similar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

ALT levels increase > AST early hepatocellular disease

A
  • AST increase is greater in alcohol-related liver disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Alanine transaminase assay useful for

A
  • Acute liver damage (like viral hepatitis)
  • Monitoring effectiveness of new treatments of liver disease
  • Cardiac failure and muscle disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

De Ritis Ratio (DRR)

A
  • AST/ALT
  • Numerical values may vary
  • May reach 6.0 in alcohol-related liver disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Increased AST/ALT ratio plasma levels are seen in

A
  • Cirrhosis
  • Liver tumors
  • Obstructive jaundice
  • Burns and shock
23
Q

Creatine kinase catalyzes

A
  • Reversible phosphorylation of creatine by ATP

- Key to phosphagen metabolism

24
Q

Creatine kinase requires

A
  • Mg++, but is inhibited by excess ADP
25
Q

Creatine kinase

A
  • Cytosol of striated muscle, brain, heart tissue

- Exists as a dimer of 2 subunits; M and B (mwt 40,000)

26
Q

Plasma CK levels are proportional to

A
  • Muscle mass
27
Q

Plasma CK assay importance

A
  • Skeletal muscle and heart disease

- Differentiation between skeletal muscle and heart disease necessitates isoenzyme assay

28
Q

Creatine kinase isoenzymes must be distinguished by

A
  • Electrophoresis
29
Q

Elevated plasma creatine kinase levels are seen in

A
  • Muscle disease
  • Myocardial infarction (10x increase)
  • Surgery, muscular trauma, heavy exercise, muscle dystrophy (5x increase)
30
Q

Creatine kinase levels of well-trained athletes will be

A
  • Lower than untrained individuals because they secrete smaller amounts
31
Q

All types of muscular dystrophy demonstrate

A
  • Increase in CK (mainly CK3, but maybe CK2)
32
Q
  • Diseases of CNS and hypothyroidism show
A
  • 5-fold increase in creatine kinase (CK3)
33
Q

Decrease in plasma CK levels is observed in

A
  • Hyperthyroidism
34
Q

Plasma Cardiac Troponin T is better than

A
  • CK-MB in diagnosis and prediction of heart failure
35
Q

Major sources of amylase

A
  • Salivary glands

- Exocrine pancreas

36
Q

Amylase

A
  • Small protein that filters well

- Measurable in urine

37
Q

Plasma amylase may be

A
  • Normal in chronic pancreatic disease

- Elevated in renal disease

38
Q

Acute pancreatitis

A
  • Caused by gallstones/alcohol

- Elevates plasma amylase (10x) and lipase activity

39
Q

Acute pancreatitis

A
  • Initially managed medically

- Other acute abdomens usually require laparotomy

40
Q

Lactate dehydrogenase (LDH)

A
  • Cytoplasm of the majority of cell types

- Concentration is 500-fold that in the plasma

41
Q

Five distinct isoenzymes of LDH exist (mwt 136kD)

A
  • Tetramers of 4 distinct polypeptide chains

- Polypeptide chain may be 1 of 2 types, H or

42
Q

Five different combinations constitute the LDH isoenzymes

A
  • H4 isoenzyme = LD1
  • M4 isoenzyme = LD5
  • All 5 found in plasma of healthy individuals
43
Q

All LDH isoenzymes catalyze

A
  • Reversible oxidation of lactate

- NAD functions as the H acceptor in the reaction

44
Q

Plasma levels of LDH isoenzymes

A
  • Healthy: LD2 > LD1 > LD3 > LD4> LD5

- Changes to this pattern in disease

45
Q

LDH 1 and 2 primarily found in

A
  • Myocardium

- Erythrocytes

46
Q

LDH 3 primarily found in

A
  • Brain

- Kidney

47
Q

LDH 4 and 5 primarily found in

A
  • Liver

- Skeletal muscle

48
Q

Classic plasma LDH changes caused by diseases

A
  • Myocardial infarction

- Hepatic, hemolytic jaundice and other liver disorders

49
Q

Myocardial infarction plasma LDH changes

A
  • LD1 & LD2 are elevated
  • 8 - 12 hours after pain begins
  • Peak at 24 - 48 hours
  • Levels remain elevated for 7-12 days and decline slowly
50
Q

LD1 and LD2 may also be elevated in

A
  • Anemia
51
Q

Specimen hemolysis may generate

A
  • LDH profile that mimics that seen in MI

- cTroponin I now often preferred assay for infarction

52
Q

Plasma LDH in hepatic anoxia, hemolytic jaundice and other liver disorders

A
  • Elevated up to 10x normal
  • LD5 most elevated (combine results with AST/ALT assay)
  • Patients with malignant disease (Muscular dystrophy) exhibit elevated serum LDH
53
Q

The most useful enzyme assays are those that can easily be measured

A
  • Spectrophotometrically

Biochemistry II (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions