CC2 LEC (P) L4: LDH and GGT

amatz shantidope

A

What reaction does Lactate Dehydrogenase (LDH) catalyze in the glycolytic pathway?

a. The reversible conversion of lactate and NAD into pyruvate and NADH.

b. The irreversible conversion of glucose into lactate.

c. The transfer of an amino group from aspartate to alpha-ketoglutarate.

d. The hydrolysis of phosphomonoesters into alcohol and phosphate.

A

Which trace element is a structural component of the Lactate Dehydrogenase enzyme?

a. Zinc

b. Magnesium

c. Copper

d. Iron

A

Which of the following accurately describes the tissue distribution of Lactate Dehydrogenase?

a. Present in almost all types of tissue; tissue non-specific.

b. Found exclusively in cardiac muscle.

c. Found only in the red blood cells and liver.

d. Limited solely to skeletal muscle and brain tissue.

A

What is the reference range for Lactate Dehydrogenase (LDH)?

a. 125-220 U/L

b. 5-35 U/L

c. 6-55 U/L

d. 300-500 U/L

A

During the conversion of Lactate to Pyruvate, what action does Lactate Dehydrogenase perform regarding hydrogen?

a. Lactate Dehydrogenase donates Hydrogen to NADH.

b. Lactate Dehydrogenase removes Hydrogen from NADH.

c. Lactate Dehydrogenase adds Hydrogen to water molecules.

d. Lactate Dehydrogenase donates Hydrogen to zinc.

A

What is the optimal pH range for the forward reaction (Lactate to Pyruvate) of Lactate Dehydrogenase?

a. 8.3-8.9 pH

b. 7.1-7.4 pH

c. 5.0-6.0 pH

d. 10.0-10.5 pH

A

What is the polypeptide subunit composition of the LDH-1 isoenzyme?

a. HHHH (4 H subunits)

b. HHHM (3 H, 1 M subunits)

c. HHMM (2 H, 2 M subunits)

d. MMMM (4 M subunits)

A

Which LDH isoenzyme is characterized by having 3 H subunits and 1 M subunit (HHHM)?

a. LDH-2

b. LDH-1

c. LDH-3

d. LDH-4

A

The LDH-3 isoenzyme is predominantly found in which of the following tissues?

a. Lung, Lymphocytes, Spleen, Pancreas

b. Heart and Red blood cells

c. Liver and Skeletal muscle

d. Brain and Kidneys

A

Which tissues are the primary source of the LDH-5 (MMMM) isoenzyme?

a. Skeletal muscle

b. Heart

c. Lungs

d. Red blood cells

A

Elevated levels of LDH-1 and LDH-2 are most commonly associated with which disorder?

a. Myocardial Infarction

b. Pulmonary embolism

c. Hepatic injury

d. Skeletal muscle injury

A

Which marker combination can be used to assess for Acute Myocardial Infarction when LDH-1 is higher than LDH-2?

a. LDH-1&2, Troponin I, and HS-CRP

b. LDH-4, AST, and ALT

c. LDH-5, CK-MM, and Myoglobin

d. LDH-3, Amylase, and Lipase

A

What is the normal concentration order of LDH isoenzymes in serum from highest to lowest?

a. LD 2 > 1 > 3 > 4 > 5

b. LD 1 > 2 > 3 > 4 > 5

c. LD 5 > 4 > 3 > 2 > 1

d. LD 3 > 2 > 1 > 5 > 4

A

Which LDH isoenzyme migrates the farthest (is the most anodal) during electrophoresis?

a. LD1

b. LD2

c. LD4

d. LD5

A

Which LDH fractions are known to be cold labile (easily destroyed in cold environments)?

a. LD4 and LD5

b. LD1 and LD2

c. LD2 and LD3

d. LD1 and LD5

A

What is the role of Alpha-hydroxybutyric dehydrogenase (HBD) in relation to LDH?

a. It has the same kinetic properties as LD1 but does not act on the substrate lactate.

b. It is an inhibitor that blocks LD5 activity in skeletal muscle.

c. It acts as a coenzyme required for the reverse reaction.

d. It represents the 6th band in electrophoresis.

A

Which enzyme is represented by the 6th band in electrophoresis (LD6) and is elevated in drug hepatotoxicity?

a. Alcohol dehydrogenase

b. Glutamate dehydrogenase

c. Malate dehydrogenase

d. Glucose-6-phosphate dehydrogenase

A

What does an elevated level of LD6 often signify in patients with atherosclerotic cardiovascular failure?

a. It can be a sign of impending death or grave prognosis.

b. It indicates successful reperfusion therapy.

c. It signifies complete recovery of cardiac function.

d. It points to an acute skeletal muscle injury.

A

An LDH form composed of four C subunits is found in which specific fluid or cells, though never detected in serum?

a. Spermatozoa and semen

b. Cerebrospinal fluid

c. Synovial fluid

d. Saliva and tea

A

During an Acute Myocardial Infarction (AMI), when does total LDH typically begin to increase?

a. 12-24 hours after the onset of AMI

b. 1-2 hours after the onset of AMI

c. 48-72 hours after the onset of AMI

d. 4-6 days after the onset of AMI

A

At what time frame does total LDH typically peak following an Acute Myocardial Infarction?

a. 48-72 hours after the onset of AMI

b. 12-24 hours after the onset of AMI

c. 4-6 hours after the onset of AMI

d. 7-10 days after the onset of AMI

A

Within how many days does total LDH normally return to baseline following an Acute Myocardial Infarction?

a. Normalizes within 10 days

b. Normalizes within 2 days

c. Normalizes within 48 hours

d. Normalizes within 30 days

A

Which condition is associated with the highest elevation of LDH (pronounced elevation, 5 or more times normal)?

a. Megaloblastic anemia (Pernicious anemia)

b. Uncomplicated viral hepatitis

c. Acute pancreatitis

d. Skeletal muscle injury

A

Which condition would typically cause a moderate elevation (3 to 5 times normal) of LDH?

a. Leukemia (ALL)

b. Nephrotic syndrome

c. Hypothyroidism

d. Cholangitis

A

What causes the pronounced elevation of LDH in Megaloblastic Anemia?

a. Folic Acid or Vitamin B12 deficiency causing abnormal, fragile megaloblasts to be destroyed in the bone marrow.

b. Acute destruction of normal mature red blood cells in the spleen.

c. Overproduction of red blood cells leading to polycythemia vera.

d. Toxic damage to the liver from severe chronic alcoholism.

B

Why should anticoagulants like oxalate be avoided for LDH testing?

a. Oxalate causes precipitation of zinc.

b. Anticoagulants can inhibit LDH.

c. Oxalate increases the pH to alkaline levels.

d. Anticoagulants artificially increase LDH1 levels.

B

What is the impact of hemolysis on a sample intended for LDH analysis?

a. It slightly increases LDH3 only.

b. Any degree of hemolysis renders a sample unacceptable, affecting total LD and the LD1/LD2 ratio.

c. It causes a false decrease in total LDH.

d. Hemolysis has no significant effect on LDH analysis.

B

How should specimens for LDH testing be stored?

a. Frozen at -20 degrees Celsius.

b. Stored at room temperature because LD5 is cold labile.

c. Refrigerated at 4 degrees Celsius.

d. Stored on ice immediately after collection.

B

Why is plasma typically not used for LDH testing?

a. Plasma contains fibrinogen which precipitates LDH.

b. Platelets have LDHs which can cause a false increase.

c. Heparin in plasma completely denatures LD1.

d. Plasma pH is too acidic for the assay.

B

In the Wacker Method for measuring LDH, what reaction is taking place?

a. Pyruvate is converted to lactate.

b. Lactate is converted to pyruvate.

c. Lactate is converted to glucose.

d. Pyruvate is converted to alanine.

B

In the kinetic measurement of the Wacker Method, what specific change is observed at 340 nm?

a. A decrease in absorbance as NADH is oxidized to NAD.

b. An increase in absorbance as NAD is converted to NADH.

c. A color change to golden brown.

d. A steady absorbance state showing no change.

B

In the colorimetric version of the Wacker Method utilizing phenazine methosulfate (PM) and nitroblue tetrazolium (NBTZ), what color is produced?

a. A yellow-orange color.

b. A positive blue-purple color.

c. A red-pink color.

d. A pale green color.

B

What color is produced in the colorimetric Wacker Method when p-nitrophenylhydrazine (PNPH) reacts with pyruvate?

a. Blue-purple

b. A golden brown color at alkaline pH

c. Cherry red

d. Deep blue

B

Which method measures the reverse reaction of LDH, where Pyruvate is converted to Lactate?

a. The Rosalki-Wilkinson method

b. The Wrobleuski-La Due method

c. The Wacker method

d. The Bowers and Mc Comb method

B

How does the Wrobleuski-La Due method measure enzymatic activity kinetically?

a. By measuring the increase in absorbance at 340 nm.

b. By measuring the decrease in absorbance at 340 nm as NADH is converted to NAD.

c. By measuring the formation of a golden brown color at 440 nm.

d. By measuring the appearance of a blue-purple color.

B

How does the reaction rate of the Wrobleuski-La Due method (P to L) compare to the Wacker method (L to P)?

a. It is 3x slower.

b. It is 3x faster than the forward reaction.

c. The rates are identical.

d. It is 10x faster.

B

What is the required pH range for the Wrobleuski-La Due (reverse) reaction?

a. 8.3-8.9 pH

b. 7.1-7.4 pH

c. 10.0-10.5 pH

d. 5.0-6.0 pH

B

What is the primary function of Gamma Glutamyl Transferase (GGT) in cellular metabolism?

a. The reversible conversion of lactate and NAD into pyruvate.

b. Involved in the transfer of the gamma glutamyl from gamma glutamyl peptides to amino acids, H2O2, and other small peptides.

c. The hydrolysis of phosphomonoesters into alcohol and phosphate.

d. The transfer of an amino group from alanine to alpha-ketoglutarate.

B

Which of the following is a known physiological role of GGT in the body?

a. It catalyzes the breakdown of glycogen in the liver.

b. Involved in peptide and CHON synthesis, regulation of tissue glutathione levels, and transport of amino acids across cell membranes.

c. It acts as an oxygen-carrying molecule in skeletal muscle.

d. It buffers the blood pH during acute metabolic acidosis.

B

Which of the following tissues are a source of Gamma Glutamyl Transferase (GGT)?

a. Cardiac muscle, skeletal muscle, red blood cells.

b. Tissues of kidney, brain, prostate, pancreas, liver.

c. Lungs, bone marrow, spleen, lymph nodes.

d. Thyroid gland, adrenal cortex, pituitary gland.

B

Clinically, GGT is recognized as a very sensitive marker for which type of disorders?

a. Primary skeletal muscle dystrophies.

b. Hepatobiliary disorders, specifically biliary tract obstruction.

c. Acute renal failure and glomerulonephritis.

d. Megaloblastic and hemolytic anemias.

B

How is GGT affected by the intake of enzyme-inducing drugs like warfarin, phenobarbital, and phenytoin?

a. The drugs cause a false decrease in GGT levels.

b. The levels increase up to 4x the upper limit of normal (ULN).

c. The drugs completely inhibit GGT activity.

d. The drugs have no effect on GGT levels.

B

In cases of chronic alcoholism, why is GGT considered a useful marker?

a. Alcohol directly destroys the GGT enzyme molecule.

b. It is a marker for alcohol rehabilitation because alcohol intake increases GGT.

c. Alcohol blocks the synthesis of GGT in the kidney.

d. GGT converts alcohol directly into acetic acid.

B

Why can GGT be elevated in acute pancreatitis and diabetes mellitus?

a. Because GGT is synthesized by the alpha cells of the pancreas only.

b. Because GGT is present in pancreatic cells, specifically in the Smooth ER.

c. Because high blood sugar activates latent GGT in the blood.

d. Because insulin therapy induces GGT production.

B

GGT is particularly useful in differentiating the cause of an elevated Alkaline Phosphatase (ALP). How do GGT levels respond in skeletal disorders or pregnancy?

a. GGT levels are pronouncedly elevated.

b. GGT levels remain normal.

c. GGT levels are moderately elevated.

d. GGT levels drop to zero.

B

When both Alkaline Phosphatase (ALP) and GGT are significantly elevated, this typically points to a disorder of which system?

a. Skeletal system (Bone disorders).

b. Hepatobiliary disorder.

c. Cardiovascular system (AMI).

d. Central nervous system.

B

Where exactly is GGT located within the hepatic architecture, making it highly sensitive for liver function tests?

a. Exclusively within the hepatocyte nucleus.

b. Present in the lining of liver canaliculi, biliary tract/ducts, and its epithelial cells.

c. Only within the Kupffer cells of the liver.

d. In the sinusoidal endothelial lining only.

B

What is the main substrate used in the diagnostic procedure for measuring GGT?

a. p-Nitrophenylphosphate (PNPP).

b. y-glutamyl-p-nitroanilide.

c. Beta-glycerophosphate (BGP).

d. Phenolphthalein diphosphate (PPDP).

B

What is the end product of the GGT analytical method that acts as a chromogen?

a. p-nitrophenol.

b. p-Nitroaniline.

c. Alpha-naphthol.

d. Phenolphthalein red.

B

What color is produced by the p-Nitroaniline end product in the GGT assay?

a. Blue-purple.

b. A strong yellow color.

c. Golden brown.

d. Cherry red.

C

At what wavelength is the yellow color produced by p-Nitroaniline typically measured?

a. 340 nm.

b. 505 nm.

c. 405 nm to 420 nm.

d. 620 nm.

C

How long is the GGT enzyme typically stable in a sample?

a. Stable for 1 day.

b. Stable for 1 month.

c. Stable only for 1 week.

d. Stable indefinitely if frozen.

C

Which of the following statements accurately describes the effect of hemolysis on GGT analysis?

a. Hemolysis causes a massive false increase in GGT.

b. Hemolysis destroys GGT activity completely.

c. GGT is not affected by hemolysis.

d. Hemolysis alters the optimal pH for the assay.

C

What is the reference range for GGT in males at 37°C?

a. 125-220 U/L.

b. 5-38 U/L.

c. 6-55 U/L.

d. 50-150 U/L.

C

What is the reference range for GGT in females at 37°C?

a. 6-55 U/L.

b. 125-220 U/L.

c. 5-38 U/L.

d. 30-80 U/L.

C

Why do females typically have a lower reference range for GGT compared to males?

a. Females have a lower overall muscle mass.

b. Females synthesize GGT in different organs than males.

c. Hormones such as Estrogen and Progesterone suppress GGT enzyme activity.

d. The female liver lacks the smooth endoplasmic reticulum required for GGT synthesis.

C

Which isoenzyme pattern is often referred to as the "LD flip" and is associated with Acute Myocardial Infarction (AMI)?

a. LD5 > LD4.

b. LD3 > LD2.

c. LD1 > LD2.

d. LD2 > LD1.

C

What is the significance of the LD1/LD2 ratio in the context of hemolysis?

a. Hemolysis causes the ratio to drop to zero.

b. Hemolysis converts all LD2 into LD1.

c. Hemolysis affects both total LD and the LD1/LD2 ratio, rendering the sample unacceptable.

d. Hemolysis only increases total LD but does not affect the ratio.

C

The Rosalki-Wilkinson method is used to measure Alpha-hydroxybutyric dehydrogenase (HBD). What specific substrate does this method use?

a. Pyruvate.

b. Lactate.

c. Ketobutyrate.

d. Gamma-glutamyl-p-nitroanilide.

C

What change is measured in the Rosalki-Wilkinson method for HBD?

a. Increase in absorbance at 405 nm.

b. Production of a blue-purple color.

c. Measurement of change in NADH absorbance.

d. Formation of a golden brown color.

C

Extensive pulmonary pneumonia would typically cause an elevation in which LDH isoenzyme?

a. LDH-1.

b. LDH-5.

c. LDH-3.

d. LDH-2.

C

Acute pancreatitis and carcinoma are associated with an increase in which LDH isoenzyme?

a. LDH-1.

b. LDH-5.

c. LDH-3.

d. LDH-4.

C

Which condition is listed under "Slight Elevation (Up to 3 times normal)" for LDH?

a. Megaloblastic anemia.

b. Myocardial infarction.

c. Most liver diseases.

d. Pulmonary infarction.

C

Which of the following conditions also causes a slight elevation (up to 3 times normal) of LDH?

a. Leukemia (ALL).

b. Systemic shock and hypoxia.

c. Hypothyroidism.

d. Infectious mononucleosis.

C

Widespread carcinomatosis, especially with metastases, causes what degree of LDH elevation?

a. Slight elevation.

b. Moderate elevation.

c. Pronounced elevation (5 or more times normal).

d. No elevation.

C

Renal infarction and Hepatitis are categorized under which level of LDH elevation?

a. Slight elevation.

b. Moderate elevation.

c. Pronounced elevation (5 or more times normal).

d. Decreased levels below normal.

C

Moderate elevation (3 to 5 times normal) of LDH is typically seen in which of the following conditions?

a. Cholangitis.

b. Nephrotic syndrome.

c. Pulmonary infarction.

d. Renal infarction.

C

Infectious mononucleosis and Delirium tremens typically cause what degree of LDH elevation?

a. Slight elevation.

b. Pronounced elevation.

c. Moderate elevation (3 to 5 times normal).

C

In the context of AMI, which alternative markers can be used alongside LDH-1 and LDH-2?

a. AST and ALT.

b. Lipase and Amylase.

c. Troponin I and HS-CRP.

d. Alkaline Phosphatase and GGT.

C

Which LDH isoenzyme is primarily composed of four M subunits (MMMM)?

a. LDH-1.

b. LDH-3.

c. LDH-5.

d. LDH-2.

C

Which LDH isoenzyme consists of two H and two M subunits (HHMM)?

a. LDH-1.

b. LDH-4.

c. LDH-3.

d. LDH-5.

C

LDH-4 is composed of which combination of polypeptide subunits?

a. Four H subunits.

b. Three H subunits and one M subunit.

c. One H subunit and three M subunits (HMMM).

d. Four M subunits.

C

Besides the liver, which organ is also a primary source of the LDH-4 isoenzyme?

a. Heart.

b. Lungs.

c. Liver (as it is one of the main sources, though the prompt implies another; LDH-4 is primarily liver-associated).

d. Brain.

C

Exercise can cause a false increase in which LDH isoenzyme?

a. LDH-1.

b. LDH-2.

c. LDH-5.

d. LDH-3.

C

Rhabdomyolysis would most likely cause a significant elevation in which LDH isoenzyme?

a. LDH-1.

b. LDH-2.

c. LDH-5.

d. LDH-3.

D

Which of the following statements about the structure of LDH isoenzymes is correct?

a. They are monomeric proteins.

b. They are dimeric molecules with 2 polypeptide subunits.

c. They are hexameric molecules with 6 subunits.

d. They are tetrameric molecules, having 4 polypeptide subunits.

D

What is the primary purpose of performing LDH electrophoresis?

a. To determine total LDH concentration in a sample.

b. To remove cold labile fractions from the sample.

c. To increase the pH of the sample prior to analysis.

d. Used for differentiation and quantifying LDH isoenzymes.

D

Which of the following conditions is associated with an elevation of LDH-1 and LDH-2, aside from AMI?

a. Acute pancreatitis.

b. Hepatic injury.

c. Skeletal muscle injury.

d. Hemolytic anemia and Megaloblastic anemia.

D

In addition to lung and lymphocytes, which other tissues contain significant amounts of LDH-3?

a. Heart and Red blood cells.

b. Liver and Skeletal muscle.

c. Kidneys and Brain.

d. Spleen and Pancreas.

D

A hemolyzed specimen would falsely elevate which LDH isoenzymes most significantly?

a. LDH-4 and LDH-5.

b. LDH-3 only.

c. LDH-6.

d. LDH-1 and LDH-2.

D

Which analytical method for LDH measures the decrease in absorbance at 340 nm?

a. The Wacker Method.

b. The Rosalki-Wilkinson method.

c. The colorimetric Wacker Method.

d. The Wrobleuski-La Due (reverse reaction) method.

D

In the colorimetric Wacker Method, what reagents are added to react with NADH to produce a blue-purple color?

a. p-nitrophenylhydrazine (PNPH).

b. y-glutamyl-p-nitroanilide.

c. Alpha-naphthyl phosphate.

d. Phenazine methosulfate (PM) and nitroblue tetrazolium (NBTZ).

D

What defines the term "LD flip" in clinical chemistry?

a. When LD5 concentration exceeds LD4.

b. When total LDH drops below the normal reference range.

c. When the reverse reaction rate exceeds the forward reaction rate.

d. When the concentration of LD1 becomes greater than LD2 (LD1 > LD2).

D

What is the significance of Gamma Glutamyl Transferase (GGT) in differentiating an elevated Alkaline Phosphatase (ALP)?

a. It determines whether the ALP is of placental or intestinal origin.

b. It is elevated in bone disease, confirming a skeletal origin.

c. It is decreased in liver disease, ruling out hepatobiliary issues.

d. It remains normal in skeletal disorders and pregnancy, but is high in hepatobiliary disorders.

D

Which of the following best describes the diagnostic utility of GGT regarding alcoholism?

a. It is only useful for diagnosing acute alcohol poisoning.

b. It is decreased in chronic alcoholics.

c. It is a marker for skeletal muscle damage caused by alcohol.

d. It is associated with chronic alcoholism and serves as a marker for alcohol rehabilitation.

D

What role does GGT play regarding glutathione?

a. It breaks down glutathione into urea and ammonia.

b. It completely inhibits the synthesis of glutathione.

c. It uses glutathione as a coenzyme for lactate conversion.

d. It is involved in the regulation of tissue glutathione levels.

D

What is the required wavelength to measure the golden brown color produced by phenylhydrazone in the colorimetric Wacker Method?

a. 340 nm.

b. 405 nm.

c. 620 nm.

d. 440 nm or 525 nm.

D

Which of the following drugs are known to be enzyme-inducing drugs that can elevate GGT levels?

a. Aspirin and Ibuprofen.

b. Penicillin and Erythromycin.

c. Insulin and Metformin.

d. Warfarin, Phenobarbital, and Phenytoin.

D

How does the activity rate of the Wacker Method compare to the Wrobleuski-La Due Method?

a. The Wacker Method is 3x faster.

b. The Wacker Method is 10x faster.

c. They have identical reaction rates.

d. The Wacker Method is slower; the Wrobleuski-La Due method is 3x faster.

D

In the GGT diagnostic procedure, what happens to the gamma glutamyl group from the substrate?

a. It is oxidized into carbon dioxide.

b. It is reduced into an alcohol.

c. It remains bound to the p-nitroaniline product.

d. It is transferred to an amino acid or small peptide.

D

Why is the assay for GGT often read at 405 nm to 420 nm?

a. To measure the oxidation of NADH.

b. To measure the reduction of NAD.

c. To detect the golden brown color of phenylhydrazone.

d. To measure the strong yellow color produced by the p-Nitroaniline chromogen.

D

What structural feature defines LDH isoenzymes as tetrameric molecules?

a. They contain four zinc atoms.

b. They are composed of four distinct enzymes combined.

c. They require four different substrates to function.

d. They have 4 polypeptide subunits, consisting of H and M types.

D

Which isoenzyme is most highly concentrated in the heart and red blood cells but migrates slightly slower than LD1?

a. LD4.

b. LD5.

c. LD3.

d. LD2.

D

What is the most appropriate storage temperature for a serum sample awaiting LDH analysis?

a. Frozen at -20°C.

b. Refrigerated at 4°C.

c. Heated to 37°C.

d. Room temperature.

D

Which LDH isoenzyme is characterized as the most cathodal, migrating the shortest distance during electrophoresis?

a. LD1.

b. LD2.

c. LD3.

d. LD5.

D

Which LDH isoenzyme has the highest concentration in normal serum, typically appearing as the thickest, darkest band on electrophoresis?

a. LD1.

b. LD3.

c. LD4.

d. LD2.

D

An acute renal infarct would likely cause an elevation in which group of LDH isoenzymes?

a. LDH-4 and LDH-5.

b. LDH-3.

c. LDH-6.

d. LDH-1 and LDH-2.

D

Which of the following is true regarding GGT and sample hemolysis?

a. Hemolysis causes a false increase in GGT.

b. Hemolysis causes a false decrease in GGT.

c. Hemolysis alters the optimal pH for the GGT assay.

d. GGT is not affected by hemolysis.

D

Which combination of tissues represents the primary sources for LDH-4 and LDH-5 respectively?

a. Heart and Lungs.

b. Red blood cells and Spleen.

c. Brain and Kidneys.

d. Liver and Skeletal muscle.

D

In addition to indicating hepatobiliary disorders or alcoholism, GGT can also be elevated in which of the following?

a. Myocardial Infarction only.

b. Skeletal muscle dystrophy and pregnancy.

c. Hemolytic anemia and renal infarction.

d. Acute pancreatitis and diabetes mellitus.