Meisenberg Ch 15, Plasma Proteins
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- 1.
Patients with von Willebrand disease have abnormal bleeding tendency of varying severity. The process that is most directly abnormal in these patients is:
- A.
Adhesion of platelets to the extracellular matrix
- B.
The synthesis of g-carboxyglutamate containing clotting factors
- C.
Contact phase activation
- D.
The extrinsic pathway of blood clotting
- E.
The cleavage of prothrombin to thrombin
Correct Answer
A. Adhesion of platelets to the extracellular matrixExplanation
von Willebrand factor binds to receptors on the platelet surface, and glues the platelets to the exposed extracellular matrix.Rate this question:
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- 2.
Heparin and warfarin can both be used to treat patients who are at risk of thrombosis. Can these agents also be used to prevent blood clotting in the test tube?
- A.
Warfarin can be used, but heparin cannot
- B.
Heparin can be used, but warfarin cannot
- C.
Both can be used
- D.
Neither can be used
Correct Answer
B. Heparin can be used, but warfarin cannotExplanation
Heparin acts on constituents of the plasma (antithrombin III and thrombin), whereas warfarin inhibits clotting factor synthesis in the liver.Rate this question:
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- 3.
Some clotting factors contain y-carboxyglutamate. The function of this unusual amino acid residue in the clotting factors is to bind calcium and to:
- A.
Increase the substrate specificity of the clotting factors, thereby preventing the incidental cleavage of other proteins
- B.
Bind the clotting factors to exposed components of the extracellular matrix
- C.
Serve as a feedback mechanism that makes the activated clotting factors sensitive to protease inhibitors
- D.
Create cleavage sites for proteolytic activations during zymogen processing
- E.
Bind the clotting factors to activated platelets
Correct Answer
E. Bind the clotting factors to activated plateletsExplanation
y-carboxyglutamate is present in those clotting factors that attach to the surface of activated platelets.Rate this question:
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- 4.
A 40-year-old woman complains to her doctor about severe generalized itching for the past 5 months. She had no other symptoms and she said that her alcohol consumption was low. She appeared to be slightly jaundiced, and a blood sample was analyzed with the following results: This patient is most likely suffering from:
- A.
Internal bleeding
- B.
Cholestatic jaundice
- C.
A pre-hepatic jaundice
- D.
Viral hepatitis
- E.
Gilbert's syndrome
Correct Answer
B. Cholestatic jaundiceExplanation
The combination of high alkaline phosphatase and high g-glutamyltransferase is typical for cholestasis. Itching is most likely caused by bile acids.Rate this question:
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- 5.
Patients with vitamin K deficiency have prolonged bleeding because several clotting factors are abnormal, including:
- A.
Factor V
- B.
Factor VIII
- C.
Factor IX
- D.
High-molecular-weight kininogen
- E.
Von Willebrand factor
Correct Answer
C. Factor IXExplanation
Most of the proteases (but not the activator proteins) in the final steps of the cascade depend on vitamin K: factors VII, IX, X, and prothrombin. These clotting factors use γ-carboxyglutamate and calcium to attach to the surface of activated platelets.Rate this question:
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- 6.
One of the important regulatory roles of thrombin is the binding to protease- activatable receptors. These G-protein coupled receptors are important for:
- A.
Platelet aggregation
- B.
Secretion of prostaglandins from endothelial cells
- C.
Secretion of thrombin from leukocytes
- D.
Formation of fibrin monomer
- E.
Contact phase activation
Correct Answer
A. Platelet aggregationExplanation
The receptor actually suffers proteolytic cleavage. This irreversible process makes physiological sense in this case, since platelet aggregation is irreversible.Rate this question:
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- 7.
Heparin inhibits blood clotting by:
- A.
Binding to fibrinogen and thereby preventing its cleavage by thrombin
- B.
Activating tissue-type plasminogen activator
- C.
Inhibiting urokinase
- D.
Inhibiting the binding of prothrombin to activated platelets
- E.
Activating antithrombin III
Correct Answer
E. Activating antithrombin IIIExplanation
In the body, heparan sulfate proteoglycans on the surface of endothelial cells can inhibit thrombus formation in intact blood vessels by this mechanism.Rate this question:
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- 8.
The blood clotting system is blocked both in patients with classical hemophilia, and as a result of high doses of coumarin-type anticoagulants. However, coumarin and related drugs can be deadly whereas hemophiliacs can live with their clotting disorder. The reason for this difference is:
- A.
Coumarin and related drugs activate the fibrinolytic system, in addition to blocking the clotting cascade
- B.
Only the intrinsic pathway of blood clotting is blocked in hemophilia, but intrinsic, extrinsic and final common pathways are all blocked in coumarin poisoning
- C.
Von Willebrand factor is abnormal in coumarin poisoning but not in classical hemophilia
- D.
Coumarin and related drugs inhibit contact phase activation in the intrinsic pathway; this process is intact in classical hemophilia
- E.
Fibrinogen is normal in classical hemophilia, but coumarin and related drugs cause the formation of structurally abnormal fibrinogen
Correct Answer
B. Only the intrinsic pathway of blood clotting is blocked in hemopHilia, but intrinsic, extrinsic and final common pathways are all blocked in coumarin poisoningExplanation
Hemophiliacs have their extrinsic and final common pathways intact.Rate this question:
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- 9.
A 32-year-old man sees the doctor because of chronic bronchitis. He used to smoke one pack of cigarettes per day for about 10 years but gave up smoking 5 years ago because of a persistent cough. Breath sounds suggest the presence of lung emphysema. The plasma protein that is most likely to be reduced in this patient is:
- A.
Y-globulins
- B.
A1-antiprotease
- C.
Ceruloplasmin
- D.
Fibrinogen
- E.
Haptoglobin
Correct Answer
B. A1-antiproteaseExplanation
a1-antiprotease is needed to prevent tissue damage by elastase and other proteases that are released from white blood cells during subclinical inflammation.Rate this question:
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- 10.
A patient presents with “blood” in the urine, but you are not sure whether the abnormal substance in the urine is hemoglobin or myoglobin. A blood test for one of the following proteins should help you to arrive at the correct conclusion:
- A.
Haptoglobin
- B.
Ferritin
- C.
Transferrin
- D.
α1-antiprotease
- E.
Hemoglobin
Correct Answer
A. HaptoglobinExplanation
Haptoglobin binds hemoglobin that is released during hemolysis, and the complex is removed by reticuloendothelial cells. This depletes circulating haptoglobin.Rate this question:
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- 11.
A 52-year-old man was brought to the emergency room by his wife, suffering with chest pain. When questioned, his wife said that the pain started about 4 hours earlier. You think that the most appropriate test to do at the time is cardiac troponin I, but find that the test kit for this is empty. At this time, which of the following enzyme analyses would give you the same information?
- A.
Creatine kinase-MM
- B.
Alkaline phosphatase
- C.
Lactate dehydrogenase
- D.
Creatine kinase-MB
- E.
Alanine transaminase
Correct Answer
D. Creatine kinase-MBExplanation
This isoenzyme is specific for the myocardium, and it rises early after the onset of chest pain.Rate this question:
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- 12.
A patient consumes an excessive amount of bicarbonates to treat his heartburn. Which of the following values for total plasma CO2 and plasma pH are expected as a result? The normal total CO2 is 22-30 mM, and the normal pH is 7.4. Plasma CO2 (mM) pH
- A.
25 7.7
- B.
15 7.6
- C.
45 7.5
- D.
55 7.4
- E.
65 7.3
Correct Answer
C. 45 7.5Explanation
The bicarbonate makes the blood slightly alkaline, and the respiratory center compensates by reduced breathing. Reduced breathing raises the plasma CO2.Rate this question:
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- 13.
Elevations in the plasma level of which of the following enzymes indicate a bone disease, assuming that the patient shows no signs of liver dysfunction?
- A.
Aspartate transaminase
- B.
Alkaline phosphatase
- C.
Amylase
- D.
γ-glutamyltransferase
- E.
Creatine kinase
Correct Answer
B. Alkaline pHospHataseExplanation
A different isoenzyme of alkaline phosphatase is elevated in cholestasis and other liver-related conditions. Determination of -glutamyl transferase would be one possibility to distinguish between cholestasis and bone disease in patients with elevated alkaline phosphatase.Rate this question:
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- 14.
A mother finds her 4-year-old daughter with a bag of rat poison. The child has already eaten almost the whole amount in the bag. It turns out that the active ingredient of the rat poison is warfarin. On seeing this child in the emergency room one hour later, what should you do?
- A.
Tell the mother that the child is going to die in a few hours
- B.
Inject a high dose of tissue-type plasminogen activator, then keep monitoring the prothrombin time over the next days
- C.
Make an exchange transfusion immediately, then keep monitoring the activated partial thromboplastin time over the next days
- D.
Transfuse fresh frozen plasma immediately, to replace the defective clotting factors
- E.
Gastric lavage and injection of a high dose of vitamin K, and keep monitoring the prothrombin time over the next days
Correct Answer
E. Gastric lavage and injection of a high dose of vitamin K, and keep monitoring the prothrombin time over the next daysExplanation
Warfarin is a competitive vitamin K antagonist. After regular consumption for a few days, or after a very high single dose, it can cause a fatal clotting disorder. This disorder develops slowly over several days, when the normal old clotting factors are gradually replaced by the defective ones that are made in the presence of the poison.Rate this question:
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- 15.
The following plasma and urine electrophoresis results were obtained from a 70-year-old man who complained to his doctor of back pain that he had had for several months, and feeling generally unwell. This patient most likely has:
- A.
Bence-Jones protein
- B.
Hypergammaglobulinemia
- C.
Waldenstrom's macroglobulinemia
- D.
Agammaglobulinemia
- E.
High levels of IgM
Correct Answer
A. Bence-Jones proteinExplanation
Bence-Jones proteins are loose immunoglobulin light chains that are formed by some patients with multiple myeloma, in addition to the complete immunoglobulin that forms the band at the right end of the patient’s plasma electrophoresis. Bence-Jones proteins are small enough to be filtered into the urine very fast, forming the right band in the patient’s urine. Because of renal excretion they are not abundant in the plasma. Since the glomerular basement membrane gets compromised in this condition, some albumin also appears in the urine.Rate this question:
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- 16.
A patient presents in the emergency room with abdominal pain. You suspect he may have acute pancreatitis. Which of the following enzyme analyses would help in confirming your diagnosis (or falsifying your hypothesis)?
- A.
Creatine kinase
- B.
Alkaline phosphatase
- C.
Lactate dehydrogenase
- D.
Cholinesterase
- E.
Amylase
Correct Answer
E. AmylaseExplanation
α–amylase is a digestive enzyme from the pancreas that leaks into the blood during destructive pancreatic diseases.Rate this question:
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- 17.
. A 2-year-old boy has a bleeding disorder that is clinically indistinguishable from classical hemophilia (hemophilia A). However, tests for factor VIII activity show a normal protein with normal biological properties. Which of the following observations would suggest that the boy has hemophilia B?
- A.
The plasma level of von Willebrand factor is reduced to 10% of normal
- B.
Injected heparin has a paradoxical pro-coagulant effect
- C.
The amino acid hydrolysate of a plasma sample contains an abnormally large quantity of y-carboxyglutamate
- D.
The boy’s blood clots when mixed with the blood of a patient with hemophilia A, but not when mixed with blood from a patient with hemophilia B
- E.
The prothrombin time is normal, but the activated partial thromboplastin time is greatly reduced
Correct Answer
D. The boy’s blood clots when mixed with the blood of a patient with hemopHilia A, but not when mixed with blood from a patient with hemopHilia BExplanation
Complementation tests can be used, based on the fact that a 50% reduction in the concentration of a single clotting factor is not sufficient to prevent clotting. Mixed blood from two patients with hemophilia B has virtually no factor IX activity, and therefore does not clot.Rate this question:
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- 18.
The immunoglobulin that is most directly involved in the symptoms of the common cold is:
- A.
IgM
- B.
IgG
- C.
IgA
- D.
IgD
- E.
IgE
Correct Answer
E. IgEExplanation
IgE binds to the surface of mast cells, and causes degranulation when it encounters a matching antigen. This occurs in allergies and during infections, when antigens of viral or bacterial origin are encounteredRate this question:
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- 19.
Antithrombin III is a circulating protease inhibitor that becomes active in the presence of:
- A.
Thromboplastin
- B.
Thrombomodulin
- C.
Heparin
- D.
Vitamin K
- E.
Urokinase
Correct Answer
C. HeparinExplanation
This is the mechanism for the anticoagulant effect of heparinRate this question:
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.JPG "A 40-year-old woman complains to her doctor about severe generalized itching for the past 5 months. She had no other symptoms and she said that her alcohol consumption was low. She appeared to be slightly jaundiced, and a blood sample was analyzed with the following results:
This patient is most likely suffering from:")
.JPG "The following plasma and urine electrophoresis results were obtained from a 70-year-old man who complained to his doctor of back pain that he had had for several months, and feeling generally unwell. This patient most likely has:")
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