biochem- block III

Question 1

difference b/w ALT & AST enzymes in lab?

Answer 1

ALT is very specific to liver where AST is also found in other organs such as heart & skeletal muscle

both are used as a general measure of liver inflammation/disease

Question 2

what is the normal value of serum AST?

Answer 2

males: 6-34 IU/L

females: 8-40 IU/L

Question 3

AST & ALT belongs to which group of enzymes?

Answer 3

transaminase enzyme

Question 4

where is AST found in the body?

Answer 4

mainly in the
- liver
- heart
- skeletal muscle
- kidneys
- brain
- RBCs

Question 5

in vivo, which cofactor is required to AST to perform its function?

Answer 5

pyridoxial phosphate

is a cofactor in the reaction and is necessary for enzyme activity

Question 6

what was AST formerly called?

Answer 6

serum glutamate oxaloacetate transaminase (SGOT)

Question 7

what is the clinical significance of serum AST estimation?

Answer 7

amount of AST in blood directly related to extent of tissue damage

after severe damage, AST levels rise in 6-10 hrs & remain high for about 4 days

elevated AST values may also be seen in disorders affecting heart, skeletal muscle, & kidney

Question 8

name few conditions in which serum AST is raised

Answer 8

• liver damage (acute viral hepatitis, toxins/drugs including acetaminophen overdose, acute fulminant hepatitis)
• hepatic/tumor necrosis
• heart damage (heart attack, heart failure)
• kidney damage
• muscle injury (muscular dystrophy, dermatomyositis, trauma)
• hemolysis

Question 9

what is the normal value of serum ALT?

Answer 9

males: less than or equal to 45 IU/L

females: less than or equal to 34 IU/L

Question 10

name few conditions in which serum ALT is raised

Answer 10

• liver cirrhosis
• hepatitis
• hepatotoxic drugs
• liver ischemia
• liver tumor
• congestive cardiac failure

Question 11

why are serum ALT level raised in liver disease?

Answer 11

normally, ALT is found inside liver cells

but if liver is inflamed/injured, ALT is released into bloodstream

Question 12

while taking blood sample for ALT, hemolysis should be avoided. why?

Answer 12

since ALT activity in RBCs is 3-5 times higher than in normal serum

hence false result may be obtained in case of hemolysis

Question 13

where is ALT found in the body?

Answer 13

• mainly in the liver
• but also in smaller amounts in kidneys, heart muscles, & pancreas

Question 14

what was ALT formerly called?

Answer 14

serum glutamic pyretic transaminase (SGPT)

Question 15

what is the clinical significance of serum ALT estimation?

Answer 15

test is done to:

• identify liver disease, esp cirrhosis & hepatitis caused by alcohol, drugs, or viruses
• helps to investigate liver damage
• find out whether jaundice was caused by a blood disorder or liver disease
• keep track of the effects of cholestrol-lowering medicines

Question 16

what is bilirubin

Answer 16

greenish yellow pigment excreted in the bile & eliminated in the feces

Question 17

where is the bilirubin formed

Answer 17

reticuloendothelial cells by the breakdown of hemoglobin which splits into heme & globin

Question 18

what is the fate of bilirubin formed?

Answer 18

80% of bilirubin combines w/ glucuronic acid to form bilirubin diglucoronide in the liver (which is conjugated bilirubin)

Question 19

what is the significance of conjugated bilirubin?

Answer 19

conjugated bilirubin is water soluble

about 10% binds w/ sulphate to form bilirubin sulphate & final 10% with variety of other substances which are finally excreted into the intestines

in the intestines, conjugated bilirubin is converted to urobilinogen by action of bacterioglucoronidases

after exposure to air urobilinogen is oxidizied to urobilin & feces to stercobilin

Question 20

what is jaundice?

Answer 20

clinical term referring to yellow appearance of skin and mucous epithelium resulting from an increased bilirubin concentration in the body fluids

it is detectable when serum bilirubin concentration increases above 3 mg/dl

Question 21

normal values of plasma bilirubin (IMP)

Answer 21

total serum bilirubin: 0.3-1.1 mg/dl (17 μmol/L)

direct (conjugated): 0.1-0.4 mg/dl

indirect (unconjugated): 0.2-0.7 mg/dl

Question 22

Name primary bile acids

Answer 22

• cholic acid (triol)
• chenodeoxychilic acid (a diol)

Question 23

what are secondary bile acids?

Answer 23

bacteria in the intestine can remove glycine & taurine from bile salts regenerating bile acids

they can also convert some of the primary bile acids into “secondary” bile acids by removing a hydroxyl group, producing deoxycholic acid from cholic acid & lithocholic acid from chenodeoxycholic acid

Question 24

what is meant by “tonicity”?

Answer 24

tonicity means ability of given solute to cause osmosis

because integrity of cell membrane depends upon ability to exert osmotic pressure

Question 25

what is meant by isotonic solution?

Answer 25

solution which exerts **same osmotic pressure** as the human plasma **0.9% saline solution** exerts same osmotic pressure as that of human plasma hence, **0.9% of saline solution is called isotonic to human plasma**

Question 26

what is meant by hypotonic solution?

Answer 26

solution which exerts **lower osmotic pressure** with respect to 0.9% of saline solution - *0.5% NaCl solution in water*

Question 27

what is meant by hypertonic solution?

Answer 27

solution which exerts **higher osmotic pressure** with respect to 0.9% of saline solution - *3.0% NaCl solution in water*

Question 28

what is the principle of the **estimation of AST** experiment?

Answer 28

*optimized modified method without PLP* **L aspartate + α-ketoglutarate → oxaloacetate + L-glutamate** (*w/ enzyme AST*) **oxaloacetate + NADH + H+ → L-Malate + NAD+** (*w/ enzyme MDH- malate dehydrogenase*) rate of NADH consumption is measured photometrically & is directly proportional to AST activity in the sample!

Question 29

normal AST:ALT ratio

Answer 29

**normal**- 2:5 **greater than 2**: alcoholic liver disease **less than 1**: acute viral hepatitis **greater than 1**: viral chronic hepatitis

Question 30

how do you calculate AST activity when given these values (absorbances) from photometry: 0: 0.451 1: 0.397 2: 0.340 3: 0.307

Answer 30

1. calculate first reading: **0-1** 2. calculate second reading: **2-1** 3. calculate third reading: **3-2** 4. find **average per min by adding all these up & dividing by 3** - this is the **λ** 5. multiply λ by **factor (F = 3236)** 6. units is **IU/L**

Question 31

what is the factor value used in ALT estimation and at what wavelength?

Answer 31

3235 (at λ = 360)

Question 32

ALT & AST activity estimation formula

Answer 32

**ALT/AST activity (IU/L) = ΔA per min x F** ALT F is 3235 ALT F is 3236

Question 33

principle of ALT estimation principle

Answer 33

*optimized modified method without PLP* **L alanine + 2-oxoglutarate → pyruvate + L-glutamate** (*w/ enzyme ALT*) *optimized modified method without PLP* **pyruvate + NADH + H+ → lactate + NAD** (*w/ enzyme LDH*) *the rate of absorbance changing at λ = 360nm is directly proportional to ALT activity*

Question 34

estimation of total bilirubin by colorimetric method **principle** + formula to calculate total bilirubin

Answer 34

caffeine releases albumin bound bilirubin by reacting with **diazotized sulphanilic acid** to form a **purplish compound diazo red** *color intensity produced is directly proportional to amount of bilirubin present* **calculation = AT x 10.8** (this is the constant)

Question 35

physical properties of bile

Answer 35

- translucent liquid - yellow or greenish yellow color - characteristic foul smell - alkaline to litmus pH - avg specific gravity is **1.040**