Deck 15: Plasma Proteins

Question 1

A 2-year-old boy has a bleeding disorder that is clinically indistinguishable from classical hemophilia (hemophilia A).However, tests for factor VIII activity reveal 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 procoagulant effect.
C)The amino acid hydrolysate of a plasma sample contains an abnormally large quantity of g-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.

Answer 1

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.

Question 2

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 hemophiliac patients 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.

Answer 2

Only the intrinsic pathway of blood clotting is blocked in hemophilia, but intrinsic, extrinsic, and final common pathways are all blocked in coumarin poisoning.

Question 3

Some clotting factors contain g-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.

Answer 3

Bind the clotting factors to activated platelets.

Question 4

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.

Question 5

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 which of the following proteins should help you to arrive at the correct conclusion?

A)Haptoglobin.
B)Ferritin.
C)Transferrin.
D)α1-Antiprotease.
E)Hemoglobin.

Question 6

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)g-Globulins.
B)a1-Antiprotease.
C)Ceruloplasmin.
D)Fibrinogen.
E)Haptoglobin.

Question 7

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 syndrome.

Question 8

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.

Question 9

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 to 30 mmol, and the normal pH is 7.4.

A)25
B)15
C)45
D)55
E)65

Question 10

A 52-year-old man was brought by his wife to the emergency room, suffering with chest pain.When questioned, his wife said that the pain had 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.

Question 11

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.

Question 12

One of the important regulatory roles of thrombin is the binding to receptors that can be activated by protease.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.

Question 13

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.

Question 14

The immunoglobulin (Ig) that is most directly involved in the symptoms of the common cold is:

A)IgM.
B)IgG.
C)IgA.
D)IgD.
E)IgE.

Question 15

Both heparin and warfarin can 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.

Question 16

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 of feeling generally unwell. This patient most likely has:

A)Bence Jones protein.
B)Hypergammaglobulinemia.
C)Waldenström macroglobulinemia.
D)Agammaglobulinemia.
E)High levels of immunoglobulin M (IgM).

Question 17

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 1 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)Perform gastric lavage, inject a high dose of vitamin K, and keep monitoring the prothrombin time over the next days.

Question 18

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.

Question 19

Elevations in the plasma level of which of the following enzymes indicate a bone disease, if the patient shows no signs of liver dysfunction?

A)Aspartate transaminase.
B)Alkaline phosphatase.
C)Amylase.
D)γ-Glutamyltransferase.
E)Creatine kinase.