Heme and Oxygen Flashcards
When discussing the Hemoglobin Oxygen Dissociation Curve we use the P50 to assess the function of the hemoglobin. What is the P50?
a. The percentage of hemoglobin that is present in a normal RBC
b.The partial pressure of oxygen in the blood at which the hemoglobin is 50% saturated
c.The 50mm Hg mark on the sigmoid curve graph
d. The partial pressure of oxygen at which Hemoglobin is 100% saturated
Correct: The partial pressure of oxygen in the blood at which the hemoglobin is 50% saturated
The curve is important because we can see changes when it shifts in terms of how much oxygen can saturate the hemoglobin
Hemoglobin A structure is:
a. 4 alpha chains
b.2 alpha chains 2 beta chains
c. 2 alpha chains 2 delta chains
d. 2 alpha chains 2 gamma chains
Correct: 2 alpha chains 2 beta chains
Normal adult Hemoglobin has 2 alpha chains and 2 beta chains as seen in the structure below.
Normal Adults have:
a. <1% Hemoglobin A, 2-3% Hemoglobin A2, 97% Hemoglobin F
b. 50% Hemoglobin A, 50% Hemoglobin A2
c. 97% Hemoglobin A, 3% Hemoglobin A2
d. 97% hemoglobin A, 2-3% Hemoglobin A2, <1% Hemoglobin F
correct = 97% hemoglobin A, 2-3% Hemoglobin A2, <1% Hemoglobin F
The key word here is NORMAL. Normal adults have a very small percentage of Hemoglobin F. There are some adults, who have persistant hereditary Hemologlobin F levels which are above 1%. We will study these individuals in the next course.
In stored red blood cells, you would expect to see what type of hemoglobin oxygen dissociation curve?
a. normal
b. shift to the right
c. shift to the left
d. No data available to know the type of curve
correct = shift to the left
In stored blood, only 12% of oxygen is released to the tissues because the level of 2,3-DPG is reduced. “Shift to the Left” is less than 25% release of oxygen.
What is the relationship of 2,3 DPG to oxygen dissociation in hemoglobin?
a. 2,3 DPG levels decrease, hemoglobin-oxygen dissociation curve shifts to the right.
b. As 2,3 DPG levels decrease, hemoglobin-oxygen dissociation curve shifts to the left
c. Changes in 2,3 DPG levels have no effect on the hemoglobin-oxygen dissociation curve.
d. 2,3 DPG concentration doesn’t change in stored red cells over time.
correct = As 2,3 DPG levels decrease, hemoglobin-oxygen dissociation curve shifts to the left.
Decreased levels of 2,3-DPG mean that the hemoglobin has a higher affinity for the oxygen, and as such less is released to the tissues. Because of Hgb’s multichain structure, the molecule is capable of a considerable amount of allosteric movement as it loads and unloads oxygen.
One of the most important controls of Hgb affinity for oxygen is the RBC organic phosphate 2,3 DPG. The unloading of oxygen by Hgb is accompanied by the widening of the space between the beta chains and the binding of 2,3 DPG on a mole per mole basis with the formation of anionic salt bridges between the beta chains.
The resulting conformation of the deoxyHgb molecule is known as the tense (T) form which has a lower affinity for oxygen. When Hgb loads oxygen and becomes oxyHgb the salt bridges are broken and beta chains are pulled together expelling 2,3 DPG. This relaxed (R) form of Hgb has a higher affinity for oxygen.
What does the presence of an increase in reticulocytes of 5% (normal range 0.5% - 2.0%) in the peripheral smear suggest about a patient’s hematopoiesis?
a. Increased reticulocyte count does not relate to changes in erythropoiesis
b. The patient’s bone marrow is releasing immature RBCs to compensate for decreased oxygen carrying capacity in the circulation, most likely in response to blood loss
c.The patient’s bone marrow is dysfunctional and can no longer support erythropoiesis
d. The patient has impaired erythropoiesis due to critically low hemoglobin levels.
Correct: The patient’s bone marrow is releasing immature RBCs to compensate for decreased oxygen carrying capacity in the circulation, most likely in response to blood loss
Reticulocytes are the last stage of eryhtropoiesis in the bone marrow before the mature RBC is produced. Release of higher than normal amounts of reticulocytes most commonly occurs in situations where the patient has diminished oxygen carrying capacity due to blood loss. Because the RBCs cannot keep the tissues oxygenated, the bone marrow releases RBCs before they are fully mature.
Blood for transfusion in the US is typically collected from ___________ donors
a. remunerated
b. coerced
c. young
d. non-remunerated
d. non-remunerated
Karl Landstiener discovered the AB blood group
True
False
correct answer: false
Karl Landsteiner, an Austrian physician, discovered the first three human blood groups, A, B, and C. Blood type C was later changed to O. His colleagues Alfred Decastello and Adriano Sturli add AB, the fourth type, in 1902.
In the late 1980’s the use of allogeneic blood dropped while the use of autologous and directed donor blood rose. What was the driving force behind this?
a. mistrust in the blood donor supply following the HIV crisis
b. safer collection methods of autologous and directed donation
c. fewer donor centers were available
d. donors were paid for giving blood
The HIV crisis had a long lasting impact on the donor supply. Many mistrusted the donor supply and began requesting autologous donation. Today autologous is rarely used since allogeneic is equivalent in safety and readily available.
Autologous and directed donations are collected in the same way as allogeneic
The 1980s called for a greater need of blood in an aging and sicker patient population
In 1970 Blood banks had moved toward an all-volunteer blood donor system.
Select the statement that is not accurate:
a. Glycophorin is a gloycoprotein which contains sialic acid
b. Sialic acid gives erythrocytes their negative charge
c. Glycophorin actively transports molecules (such as anions) across the RBCs lipid bilayer
d. Glycophorin functions as a receptor for the RBC
Two of the most important protein constituents of the RBC membrane include glycophorin, an integral membrane protein, and spectrin, a peripheral membrane protein. Glycophorin is the principal RBC glycoprotein, representing approximately 20# of the total membrane protein. The molecule contains approximately 60% carbohydrate and accounts for most of the membrane sialic acid, which gives the erythrocytes their negative charge. As a result, RBCs repel each other as they move through the circulation. Glyocophrin, similar to other integral membrane proteins, spans the entire thickness of the lipid bilayer and appears on the external surface of the RBC membrane, accounting for the location of many RBC antigens. Most of these proteins… carry RBC antigens and are receptors (such as glycophrins) or transport proteins (such as the anion-exchange channel glycoprotein). (Chapter 3 page 66 Harmening Hematology) “
Glycophorins are primarily receptor proteins, not transport proteins
The body contains iron. Iron is primarily acquired from food intake. Some of the iron supply in our bodies is bound to heme in the hemoglobin molecule. What fraction is bound to heme?
a. 2/3
b. 50%
c. 100%
d. 1/3
Two thirds of the the total body iron supply is bound to heme in the hemoglobin molecule.
