Module 5 quiz questions
'The bicarbonate acts to increase pH, which may allow hemoglobin to transport oxygen more efficiently'. -The addition of bicarbonate will increase pH, which alleviates the acidosis caused by cardiac arrest. A differential (high versus low) in pH levels is needed for hemoglobin to effectively transport oxygen in the body.
Acidosis occurs as a result of cardiac arrest. Which of the following is the theoretical reason why sodium bicarbonate might be administered to your patient during a cardiac arrest?
High affinity for CO -Carbon monoxide (CO), which is similar in shape to oxygen (O2), binds to the iron (Fe) atom in the heme group when hemoglobin is in the R state and the heme group is planar, just like oxygen does. Hemoglobin binds to carbon monoxide with 200 times the affinity of oxygen, which means it is very difficult to get rid of the carbon monoxide once it is bound to hemoglobin.
Does oxygenated hemoglobin have a high or low affinity for carbon monoxide (CO)?
Iron. -Hemoglobin contains 4 heme groups, each of which contains an iron atom. Oxygen binds directly to the iron atom in the heme group.
Hemoglobin and myoglobin proteins bind molecular oxygen. The protein subunit of hemoglobin does not bind directly to the oxygen. Instead, a specific atom binds oxygen. In hemoglobin, which of the following will directly bind oxygen?
Hemoglobin has a sigmoidal curve, whereas myoglobin has a hyperbolic curve -Since hemoglobin binds oxygen in a cooperative manner, it has a sigmoidal curve, whereas myoglobin only binds one molecule of oxygen, so it has a hyperbolic curve.
Hemoglobin transports oxygen and myoglobin stores oxygen. They exhibit different oxygen-binding curves when plotted on a graph with total partial pressure of the oxygen (x-axis) plotted against the percent saturation of hemoglobin (y-axis). What is the shape of the oxygen-binding curves for hemoglobin and myoglobin?
25, 90% -Using the graph, 50% hemoglobin saturated with oxygen can be found on the y-axis at 0.5. This point corresponds with ~25 mm Hg on the x-axis. At 25 mm Hg, the myoglobin curve has a y-axis value of ~ 90%.
Based on the graph (shown above), 50% of Hemoglobin is saturated with oxygen at approximately ________ mm Hg and _____________% of myoglobin is saturated with oxygen at the same concentration.
'iron' -Carbon monoxide and oxygen bind hemoglobin by binding to the iron atom that is located at the center of the heme group.
Carbon monoxide outcompetes oxygen for attachment to the _______hemoglobin where it binds tightly.
'enzyme, bicarbonate ions' -Carbonic anhydrase is an enzyme (its name ends with -ase) and it allows carbon dioxide to travel to the lungs in the form of bicarbonate since carbon dioxide itself does not travel through the blood.
Carbonic anhydrase is an important ________ present in the red blood cells that aids in efficient transportation of carbon dioxide in the form of _________, from tissues to lungs.
excess H+ -H+ causes blood pH to drop and become acidic. Hemoglobin binds to H+ which not only causes O2 to be released to the tissues but also buffers the blood to allow the pH to increase.
Hemoglobin acts as a buffer to prevent blood from becoming too acidic by binding ___.
'An increase in H+ concentration and decrease in pH will shift hemoglobin's oxygen-binding curve to the right, while a decrease in H+ concentration will shift the curve to the left'. An increase in H+ concentration lowers the pH and leads hemoglobin to be more in the T state with lower oxygen affinity, so the curve will shift right. Alternatively, a decrease in H+ concentration raises the pH and leads hemoglobin to be more in the R state with higher oxygen affinity, so the curve will shift left.
Due to the Bohr effect, how will the curve shown shift in response to changes in pH?
'curve b'. While Curve D has the S-shaped (sigmoidal) curve characteristic of hemoglobin, since it is to the right of Curve C, it has a lower affinity for oxygen. Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin to enhance the fetus' ability to obtain oxygen from the mother. Therefore, the fetal hemoglobin oxygen binding curve will be shifted to the left, not the right, of the adult hemoglobin curve (Curve C).
Gas exchange between maternal blood and fetal blood takes place in the placenta. If curve c in the following graph represents the dissociation curve of adult hemoglobin, which curve would represent the dissociation curve of fetal hemoglobin?
H+ ions -Hemoglobin can regulate pH by binding to H+.
Hemoglobin acts as a buffer and controls the pH of the blood by binding _____.
Excess protons, high carbon dioxide -Favoring deoxygenated hemoglobin means oxygen is being delivered or released from hemoglobin. When the tissues are using O2 to make ATP, CO2 is a byproduct. As CO2 accumulates in the blood it is converted to bicarbonate and H+ (protons). It's the build-up of H+ that lowers the pH and also initiates the release of oxygen from hemoglobin. Thus, high CO2 means excess H+, lower pH, and delivery of O2.
Identify the factors that favor the deoxygenated form of hemoglobin.
'In a firefighter who is brought to the emergency room after entering a burning building'. -The planar conformation of heme would be favored under conditions of high pH (at high pH, hemoglobin prefers to bind oxygen and heme is in the planar conformation). A hospitalized firefighter would presumably be exposed to carbon monoxide and receiving oxygen and would thus have more hemoglobin in the oxygen-binding conformation (R-state).
In which of the following patients is the planar conformation of the heme group in hemoglobin favored?
One, Four -Myoglobin has one subunit and hemoglobin has four subunits.
Myoglobin and hemoglobin each have different numbers of subunits and this affects their respective oxygen storage and delivery capabilities. How many subunits does myoglobin have versus hemoglobin?
Myoglobin has a higher affinity for oxygen than hemoglobin. -Since myoglobin stores oxygen, it has a higher affinity for oxygen. Hemoglobin's lower affinity for oxygen allows hemoglobin to release oxygen to the tissues at a lower blood pH.
Myoglobin stores oxygen, whereas hemoglobin transports oxygen. Which of the following statements accurately describes the affinity of myoglobin and hemoglobin for oxygen?
Hb binds to CO with a higher affinity than oxygen and stabilizes the R-state. -Hemoglobin binds 200-times more strongly to CO than oxygen and When CO binds to hemoglobin, it stabilizes the R-state of the protein. The R state of hemoglobin is responsible for the pink or cherry red color observed in CO poisoning.
Patients with carbon monoxide (CO) poisoning may exhibit pink or cherry red skin, mucous membranes, and nails. Which statement accurately describes hemoglobin's role in CO poisoning?
'hydrophobic' -In Sickle Cell Anemia, the beta hemoglobin gene contains a mutation where glutamate is changed to valine (a hydrophobic amino acid), which affects the hydrophobic patches of deoxygenated hemoglobin. Cysteine is also mildly hydrophilic so replacing like with like is not likely to cause significant changes in protein structure.
Patients with sickle cell anemia have atypical hemoglobin, which will distort the red blood cells into sickle shape during oxygen delivery. The substitution of a hydrophilic amino acid with a _______ amino acid in hemoglobin subunits results in the polymerization of hemoglobin, leading to the sickling of red blood cells.
Binds oxygen tightly at lower oxygen concentrations -Fetal hemoglobin is preferentially in the R-state and is capable of binding oxygen at lower oxygen concentrations. This allows fetal hemoglobin to receive oxygen from maternal hemoglobin.
The structure of fetal hemoglobin allows it to have a higher affinity for oxygen when compared to maternal hemoglobin. Which of the following accurately describes fetal hemoglobin?
0.7
Tissues at rest have an oxygen concentration of 40 Torr. What is the fraction of hemoglobin with oxygen bound (hemoglobin saturation) at 40 torr and at pH 7.2?
pH decreases, Hb shifts more to the T state, oxygen affinity decreases -The pH decreases as CO2 increases, when the CO2 combines with water to form H+ and bicarbonate, and decreasing pH favors the T state and low affinity.
What happens to oxygenated hemoglobin as the amount of CO2 increases?
CO2 decreases from exhalation, thus the pH of the lungs increases. -The CO2 in the lung decreases as we exhale and the H+ that was on hemoglobin is recombined with the bicarbonate ion which produces CO2 and H2O. The acidic H+ is now part of water, which is neutral, thus increasing the pH.
What is happening to the pH of the lungs due to exhalation?
CO2 increases from aerobic metabolism, thus the pH of the muscles decreases. -During aerobic exercise, CO2 is released by the tissues and as a result the CO2 increases. This, in turn, results in the CO2 combining with H2O to produce a bicarbonate ion and a proton (H+). This increase in protons, thus lowers the pH.
What is happening to the pH of the muscles due to aerobic exercise?
'1' -Hemoglobin's structure changes from T to R-state upon binding of one oxygen molecule.
What is the number of oxygen molecules that must bind in order for hemoglobin to shift to the R-state (relaxed state)?
Cooperativity -Cooperative requires the subunits of hemoglobin to work together so they all release O2 at the same time or are all binding O2 at the same time. Since myoglobin contains only one subunit, there is no other group to "cooperate" with. Therefore, cooperativity is a feature demonstrated by hemoglobin and not myoglobin.
What property of hemoglobin, not observed in myoglobin, enables hemoglobin to be an effective oxygen delivery molecule?
"Its affinity for oxygen is regulated by pH". -Myoglobin is a storage protein, whereas hemoglobin is a delivery protein. This means that hemoglobin will have a lower affinity for O2 because it needs to release it to tissues.
Which feature of hemoglobin makes it an effective oxygen transport molecule?
B. While A shows an O2 saturation of 50% (y-axis), the dashed line represents a myoglobin curve (hyperbolic in shape). Since myoglobin is found in the muscles and not in the blood, this would not represent a pulse oximetry measurement of blood. B is a hemoglobin curve (sigmoidal in shape) and is representing an O2 saturation of 50%.
Which letter depicts a pulse oximetry measurement of blood with an O2 saturation of 50%?
'CO'. -Carbon monoxide binds to hemoglobin with a higher affinity than oxygen. Carbon dioxide binds to hemoglobin to a lesser extent and myoglobin binds oxygen with high affinity.
Which of the following binds hemoglobin with the highest affinity?
'oxygen' -In addition to oxygen, carbon monoxide (CO) can bind directly to the iron atom.
Which of the following components can bind directly to the iron atom in hemoglobin?
planar heme group, relaxed state, high pH, subunits are closer together -When hemoglobin binds oxygen, it is in the R-state and heme is the planar conformation. Hemoglobin binds oxygen in the lungs, where the pH is high.
Which of the following favor the oxygenated form of hemoglobin?
Hemoglobin can bind subsequent molecules of oxygen more easily after the first oxygen molecule binds. -The four subunits of hemoglobin work cooperatively to bind or release oxygen.
Which of the following statements accurately describes cooperativity?
'As 2,3-BPG decreases or pH increases, hemoglobin's affinity for oxygen increases.' -pH is positively correlated to the affinity of hemoglobin for oxygen (the Bohr effect), so as the pH increases, the affinity will also increase. 2,3-BPG is produced by pregnant mothers and people who live at high altitudes and stabilizes the low affinity deoxygenated T state of hemoglobin. This makes it easier for the hemoglobin to deliver oxygen to the developing fetus or tissues that need oxygen in a high-altitude, low oxygen environment.
Which of the following statements are true?
'Relative to the lungs, the pH in the peripheral tissues is lower because the CO2 generated by metabolism is converted to bicarbonate, which releases protons (H+)' -Carbonic anhydrase is the enzyme that catalyzes the combination of CO2 (released from the citric acid cycle by the breakdown of carbohydrates and fats) and water to form bicarbonate and H+ (protons). Therefore, carbonic anhydrase makes H+ (protons), not binds them.
Which statement describes the relationship between the pH in the lungs and peripheral tissues?
'At the lower pH of an actively metabolizing tissue, hemoglobin has a lower affinity for oxygen'. Oxygen concentration does not affect the pH. pH is a measure of the proton (H+) concentration, with high H+ resulting in low pH. CO2 does affect pH by combining with water to form bicarbonate and protons (H+); high CO2 results in high H+ and therefore low pH. The Bohr effect states that hemoglobin at low pH has a low affinity for oxygen, so oxygen will be released, not bind to, hemoglobin in actively metabolizing tissues.
Why is more oxygen unloaded from hemoglobin in an actively metabolizing tissue than in a resting tissue, even at the same concentration of O2?