CC2 AST, ALT, AMMONIA

c

In the human bloodstream, free ammonia predominantly exists in equilibrium as which chemical form?
a) Ammonium hydroxide
b) Nitrogen gas
c) Ammonium ion (NH4)
d) Urea
e) Glutamate

b

Which organ is primarily responsible for the metabolic clearance of ammonia by converting it into non-toxic urea?
a) Kidney
b) Liver
c) Skeletal muscle
d) Intestines
e) Brain

d

A child presents with severe encephalopathy and fatty liver degeneration following a viral infection and aspirin use. This condition is known as:
a) Cirrhosis
b) Wilson's Disease
c) Infectious Mononucleosis
d) Reye's Syndrome
e) Myocardial Infarction

a

According to the provided table, the enzymatic method (GLDH) for ammonia measurement detects a decrease in absorbance at which wavelength?
a) 340 nm
b) 405 nm
c) 505 nm
d) 450 nm
e) 540 mm

a

To prevent the deamination of amino acids and bacterial metabolism in an ammonia specimen, what is the critical first step after collection?
a) Immediate chilling in an ice slush (0-4C)
b) Exposure to ambient laboratory air
c) Keeping the sample at room temperature
d) Using a prolonged tourniquet during collection
e) Centrifuging at $37^{\circ}C$

b

Why is hemolysis strictly unacceptable for ammonia analysis?
a) RBCs consume ammonia as an energy source
b) RBCs contain 2 to 3 times higher ammonia concentration than plasma
c) Hemolysis causes the specimen to turn blue
d) Hemolysis prevents the formation of urea
e) Hemolysis activates GLDH prematurely

a

Which patient preparation is mandatory before venipuncture for ammonia levels due to the high ammonia content in the product used?
a) Abstaining from smoking
b) Fasting for 12 hours
c) Strenuous exercise
d) Drinking ethanol
e) Taking barbiturates

c

Which analytical method for ammonia exploits the volatility of $NH_3$ gas diffusing into an acid/pH indicator solution?
a) Ion-Selective Electrode
b) Colorimetric Bromophenol Blue
c) Conway Microdiffusion
d) Wroblewski & LaDue
e) Reitman-Frankel

d

In the urea cycle, parenchymal cells of the liver consume ammonia to synthesize which non-toxic compound?
a) Alanine
b) Oxaloacetate
c) Creatine
d) Urea
e) Pyruvate

e

Which class of enzymes catalyzes the joining of two substrate molecules coupled with ATP hydrolysis?
a) Oxidoreductases
b) Hydrolases
c) Lyases
d) Isomerases
e) Ligases

b

What is the optimal pH range for most human enzymes, excluding exceptions like Acid Phosphatase?
a) 4.5–5.5
b) 7.0–8.0
c) 9.8–10.5
d) 1.0–2.0
e) 12.0–13.0

a

Under zero-order kinetics, the reaction velocity becomes independent of substrate concentration and depends strictly on:
a) Enzyme concentration
b) Temperature
c) pH
d) Product concentration
e) Time

c

Aspartate Aminotransferase (AST) was formerly known by which name?
a) SGPT
b) ALP
c) SGOT
d) LDH
e) GGT

d

Which coenzyme is a required secondary substrate for both AST and ALT catalytic activity?
a) NADH
b) Magnesium ions
c) NADPH
d) Pyridoxal Phosphate (Vitamin B6)
e) Flavin adenine dinucleotide

e

What is the clinical significance of a De Ritis ratio (AST/ALT) greater than 2.0?
a) Acute Viral Hepatitis
b) Normal Liver Function
c) Chronic Liver Disease
d) Obstructive Jaundice
e) Alcoholic Hepatitis or Hepatocellular Carcinoma

b

In the Karmen method for AST measurement, which coupled enzyme is used to facilitate the indicator reaction?
a) Lactate Dehydrogenase
b) Malate Dehydrogenase
c) Glutamate Dehydrogenase
d) Amylase
e) Lipase

a

Which of the following is the primary cellular location of Alanine Aminotransferase (ALT)?
a) Cytoplasm exclusively
b) Mitochondria exclusively
c) 60% Cytoplasm and 40% Mitochondria
d) Nucleus
e) Cell membrane

c

An AST level that rises 6 to 8 hours post-chest pain and peaks at 24 hours is highly suggestive of:
a) Viral Hepatitis
b) Cirrhosis
c) Acute Myocardial Infarction
d) Biliary Obstruction
e) Muscular Dystrophy

d

Which enzyme class does Lactate Dehydrogenase (LDH) belong to?
a) Transferases
b) Hydrolases
c) Isomerases
d) Oxidoreductases
e) Lyases

e

At what temperature does the thermal energy typically begin to unfold an enzyme's protein structure completely, causing permanent loss of activity?
a) 0 C
b) 25 C
c) 37 C
d) 15 C
e) 40-50 C

b

Which anticoagulant is specifically avoided when collecting blood for ammonia testing?
a) EDTA
b) Ammonium Heparin
c) Lithium Heparin
d) Sodium Heparin
e) Sodium Citrate

a

In enzymology, the region where regulatory molecules bind and change the enzyme's conformation is the:
a) Allosteric Site
b) Active Site
c) Substrate Site
d) Catalytic Center
e) Transition State

c

Which enzyme catalyzes the cleavage of bonds by the addition or removal of water?
a) Isomerases
b) Transferases
c) Hydrolases
d) Ligases
e) Oxidoreductases

d

A De Ritis ratio of <1.0 is most commonly associated with which condition?
a) Alcoholic Hepatitis
b) Cirrhosis
c) HCC
d) Acute Viral Hepatitis
e) Myocardial Infarction

e

The Reitman-Frankel method for AST/ALT measurement uses which color developer?
a) Bromophenol Blue
b) Diazonium Salt
c) Malate Dehydrogenase
d) NADH
e) 2,4-dinitrophenylhydrazone (DNPH)

a

Which of the following is considered a source of ammonia production in the body?
a) Intestinal bacterial metabolism
b) Urea cycle in the liver
c) In vitro separation of plasma
d) Hyperalimentation therapy
e) Conversion of glutamate to oxaloacetate

a

The measurement of urine ammonia is primarily used to assess the capacity of which organ to maintain acid-base balance?
a) Kidney
b) Liver
c) Lungs
d) Pancreas
e) Spleen

c

Which enzyme class is responsible for the structural rearrangement of geometric or optical isomers?
a) Hydrolases
b) Transferases
c) Isomerases
d) Lyases
e) Oxidoreductases

d

In the Wroblewski & LaDue method for ALT, what is the indicator reaction?
a) LDH reduces pyruvate to lactate while oxidizing NADH to NAD+
b) MDH oxidizes oxaloacetate to malate
c) GLDH produces glutamate from ammonia
d) DNPH reacts with pyruvate to form a blue color
e) Bromophenol Blue forms a blue complex with ammonia

e

What is the adult reference interval for plasma ammonia?
a) 5-35mu g/dL
b) 7-45mu g/dL
c) 68-136mu g/dL
d) 140-1500mg/day
e) 19-60mu g/dL

Which inorganic activators are common metallic cofactors required for enzyme activity?
a) Vitamins
b) Mg2 and Zn2
c) NADH and NADPH
d) Glucose and Maltose
e) Amino acids

a

In first-order kinetics, the reaction rate is directly proportional to:
a) Substrate concentration
b) Enzyme concentration
c) Temperature only
d) Time elapsed
e) Atmospheric pressure

c

Which enzyme class does AST and ALT belong to?
a) Oxidoreductases
b) Isomerases
c) Transferases
d) Lyases
e) Hydrolases

d

Mitochondrial AST is released specifically during which pathological process?
a) Normal cellular turnover
b) Mild viral infection
c) First-order kinetics
d) Severe tissue necrosis
e) Allosteric activation

e

Which factor can cause a false decrease in plasma ammonia levels?
a) Tobacco smoke
b) Lab air contamination
c) Diuretics
d) Detergents
e) Lactobacillus acidophilus

b

In the AST reaction, the amino group is transferred from L-aspartate to which alpha-keto acid?
a) Pyruvate
b) a-ketoglutarate
c) Oxaloacetate
d) L-glutamate
e) Malate

a

Which tissue contains the highest concentration of AST?
a) Heart muscle, liver, and skeletal muscle
b) Kidney and lungs
c) Brain and skin
d) Intestines and stomach
e) Spleen and pancreas

c

What is the optimal pH for Acid Phosphatase (ACP)?
a) pH 7.4
b) pH 10.0
c) pH 5.0
d) pH 8.5
e) pH 2.0

d

The removal of groups from substrates without hydrolysis, leaving double bonds, is catalyzed by:
a) Isomerases
b) Ligases
c) Transferases
d) Lyases
e) Hydrolases

e

What is the end product of the ALT reaction when alpha-ketoglutarate receives an amino group?
a) Pyruvate
b) L-aspartate
c) Oxaloacetate
d) NADH
e) L-glutamate

b

Which clinical example is categorized under the class of Hydrolases?
a) Creatine Kinase (CK)
b) Alkaline Phosphatase (ALP)
c) Pyruvate Decarboxylase
d) DNA Ligase
e) Malate Dehydrogenase

a

How does an allosteric activator affect an enzyme?
a) It changes an inactive active site into a functional conformation
b) It prevents substrate binding by blocking the active site
c) It denatures the protein structure at $37^{\circ}C$
d) It acts as a secondary substrate to be consumed
e) It decreases the reaction rate by binding to the active site

c

Which of the following is a source of error that increases plasma ammonia?
a) Levodopa
b) Diphenhydramine
c) Reagent contamination
d) Lactulose
e) Cold centrifugation

d

Severe false elevation in AST results is most often caused by:
a) Fasting
b) Mild exercise
c) Chilling the sample
d) Hemolysis
e) Storing at 4C

e

In the Reitman-Frankel method, what acts as the color intensifier to yield a blue-colored hydrazone?
a) 2,4-DNPH
b) Diazonium Salt
c) NADH
d) Pyridoxal Phosphate
e) 0.4 N NaOH

e

AST levels that are markedly elevated (>5x the Upper Limit of Normal) are typical of:
a) Pericarditis
b) Cirrhosis
c) Slight muscle strain
d) Common cold
e) Acute hepatocellular damage

d

What is the required coenzyme for ALT to transfer an amino group from Alanine?
a) ATP
b) NAD+
c) Mg2+
d) Pyridoxal Phosphate
e) NADPH

c

Why is the AST/ALT ratio (De Ritis) helpful in diagnosing alcoholic hepatitis?
a) Alcohol specifically inhibits ALT in the cytoplasm
b) Alcohol stimulates the production of urea
c) Alcohol damages mitochondria, causing mitochondrial AST leakage
d) Alcohol increases first-order kinetics in the liver
e) Alcohol acts as an allosteric inhibitor of LDH

b

Which method for ammonia is characterized by membrane stability issues and high accuracy?
a) Conway Microdiffusion
b) Ion-Selective Electrode (ISE)
c) Bromophenol Blue
d) Karmen Method
e) GLDH Gold Standard

a

Enzyme activity in the plasma is a vital biomarker for disease because:
a) Tissue injury causes intracellular enzymes to leak into plasma
b) Enzymes are naturally high in plasma during health
c) Enzymes are consumed by the disease itself
d) Plasma enzymes are necessary for allosteric inhibition
e) Healthy cells constantly secrete enzymes into the bloodstream