Enzymes and Clinical Enzymology Flashcards
(80 cards)
A 52 year old man is brought to the emergency room by his wife because of 4 hour history of chest pain. He had a myocardial infarction (MI) two years ago. His ECG does not indicate an acute MI and blood samples are obtained. The serum troponins, total creatine kinase (CK) and CK-MB are estimated in the blood samples. Which of the following best describes the role of these markers?
A. Total serum CK is an injury marker specific for MI
B. Increase of serum CK-MB but not of total CK indicates rhabdomyolysis
C. Serum CK-MB larger than 3% of total serum CK can indicate an acute MI
D. A low ratio of CK-MB to total CK indicates a severe MI
E. Serum levels of CK-MB but not total serum CK are increased after an acute MI
C. Serum CK-MB larger than 3% of total serum CK can indicate an acute MI
A 28 year old woman is brought to the emergency department with a 5 hour history of chest pain. A provisional diagnosis of myocardial infarction is made. An ECG is performed and blood is drawn for the measurement of various injury markers. Which of the following biomarkers would be most useful at this time to confirm the diagnosis?
Troponin-I
A 25 year old man comes to the physician because of a 2 week history of weakness while climbing stairs. Physical examination shows bilateral atrophy of the quadriceps and calves and diagnosis of skeletal muscle dystrophy is made. Laboratory studies show high levels of serum creatine kinase (CK). Which of the following best describes this enzyme?
Uses creatine phosphate as a substrate during muscle contraction.
A 25 year old woman comes to the physician because of a 3 day history of abdominal pain, loss of appetite and fever. Physical examination shows right upper abdominal tenderness and jaundice. A provisional diagnosis of acute liver disease is made. Blood samples are obtained for marker analysis. Elevation of which of the following enzyme levels would most likely confirm the diagnosis in this patient?
Alanine aminotransferase (ALT)
A 50 year old man is prescribed a low-dose of aspirin (81 mg/day) to prevent cardiovascular disease. Aspirin (acetyl salicyclic acid) is an irreversible enzyme inhibitor. Which of the following enzymes is most likely inhibited by this drug?
A. Acetylcholinesterase
B. Thromboxane synthase
C. HMG CoA reductase
D. Xanthine oxidase
E. Cyclooxygenase
Cyclooxygenase
A 65 year old woman has mild cardiovascular disease and is prescribed low-dose aspirin daily to reduce her blood clotting. Which of the following best describes the rationale for this treatment?
Reduces synthesis of thromboxane
A research group investigates an allosteric enzyme which does not follow Michaelis-Menten kinetics. Kinetics of the enzyme is plotted with the velocity on the Y-axis and the substrate concentration on the X-axis. Which of the following best describes the kinetics of this enzyme?
Sigmoidal due to a cooperative effect of the substrate.
A research group investigates the isozymes of creatine kinase and lactate dehydrogenase as possible serum markers in patients with myocardial infarction. Which of the following best describes the use of LDH in these patients?
LDH1/LDH2 ratio increases following an infarction
With a provisional diagnosis of acute pancreatitis, which of the following laboratory findings would most likely confirm this diagnosis?
High lipase: amylase ratio.
A research group investigates the regulation of a specific enzyme of intermediary metabolism. It is observed that the enzyme is regulated by phosphorylation by protein kinase A. Which of the following amino acid residues in the enzyme is most likely modified in this type of regulation?
A. Tyrosine
B. Glutamate
C. Serine
D. Methionine
E. Asparagine
Serine
A research group investigates the regulation of an enzyme of the glycolysis pathway. It is observed that the enzyme activity is regulated by the presence of allosteric modulators. It is observed that addition of a modulator results in feedback inhibition of the enzyme. Which of the following best describes this modulator?
Decreases enzyme affinity for its substrate
A research group investigates the role of creatine phosphate in skeletal muscle tissue. Which of the following best describes this intermediate?
Formed by creatine kinase when [ATP] levels are high.
A research group studies the reaction catalyzed by trypsin for general study of enzymology. Which of the following best describes this enzyme?
Activity is dependent on the pH of the medium
Glycogen Synthase
Glycogen synthesis
Phosphorylase b kinase
Glycogen breakdown
Pyruvate kinase
Glycolysis
Pyruvate dehydrogenase complex (type L)
Pyruvate to acetyl-CoA
Hormone-sensitive lipase
Triacylglycerol mobilization and fatty acid
Phosphofructokinase-2/fructose 2,6-bisphosphatase
Glycolysis/gluconeogenesis
Tyrosine hydroxylase
Synthesis of L-DOPA, dopamine, norepinephrine, and epinephrine
Histone H1
DNA condensation
Histone H2B
DNA condensation
Cardiac phospholamban (a cardiac pump regulator)
Regulation of intracellular (Ca2+)
Protein Phosphatase-1 inhibitor-1
Regulation of protein dephosphorylation
