MCAT Biology : Hemoglobin, Blood Cells, and Blood Proteins
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Example Question #11 : Hemoglobin, Blood Cells, And Blood Proteins
Which of the following changes in blood properties would not decrease the affinity of hemoglobin for oxygen?
Increased blood 2,3-bisphosphoglycerate
Decreased blood pH
Increased temperature
Decreased partial pressure of carbon dioxide
Decreased partial pressure of carbon dioxide
Several factors are capable for shifting the oxygen dissociation curve. A decrease in pH or an increase in carbon dioxide partial pressure indicates a need to remove carbon dioxide wastes from the system. Hemoglobin affinity for oxygen will decrease under these conditions in order to accommodate the carbon dioxide for removal. Decreased carbon dioxide partial pressure will increase the affinity for oxygen rather than decrease it.
Increased temperature and increased 2,3-bisphosphoglycerate will also decrease the hemoglobin affinity for oxygen.
A decrease in binding affinity shifts the oxygen dissociation curve to the right, while an increase shifts the curve to the left.
Example Question #901 : Biology
Hemoglobin is the principal oxygen-carrying protein in humans. It exists within erythrocytes, and binds up to four diatomic oxygen molecules simultaneously. Hemoglobin functions to maximize oxygen delivery to tissues, while simultaneously maximizing oxygen absorption in the lungs. Hemoglobin thus has a fundamentally contradictory set of goals. It must at once be optimized to absorb oxygen, and to offload oxygen. Natural selection has overcome this apparent contradiction by making hemoglobin exquisitely sensitive to conditions in its microenvironment.
One way in which hemoglobin accomplishes its goals is through the phenomenon of cooperativity. Cooperativity refers to the ability of hemoglobin to change its oxygen binding behavior as a function of how many other oxygen atoms are bound to the molecule.
Fetal hemoglobin shows a similar pattern of cooperativity, but has unique binding characteristics relative to adult hemoglobin. Fetal hemoglobin reaches higher saturation at lower oxygen partial pressure.
Because of cooperativity, adult and fetal oxygen-hemoglobin dissociation curves appear as follows.
Beyond its ability to carry oxygen, hemoglobin is also effective as a blood buffer. The general reaction for the blood buffer system of hemoglobin is given below.
H+ + HbO2 ←→ H+Hb + O2
Based on the above graph, which of the following would be expected when oxygen unloads from hemoglobin?
The remaining oxygen atoms bind with the same affinity
Hemoglobin changes conformation only when the last oxygen is unloaded
Hemoglobin does not change conformation
The remaining oxygen atoms bind with lower affinity
The remaining oxygen atoms bind with higher affinity
The remaining oxygen atoms bind with lower affinity
The basic idea of cooperativity is that oxygen will bind with lower affinity once an oxygen atom is removed. Once you remove the first oxygen atom, the remaining ones are more likely to come off to supply tissue. This change is instigated by conformational changes in hemoglobin structure when an oxygen is removed.
Example Question #12 : Hemoglobin, Blood Cells, And Blood Proteins
Fetal circulation differs greatly from that of adults. For example, a fetus does not actually have functional lungs until birth, and instead receives oxygen from the mother umbilical vein. Which is not an adaptation of the fetal circulatory system?
The foramen ovale
The ductus venosus
Fetal myoglobin has a comparatively low affinity for oxygen
The ductus arteriosus
Fetal hemoglobin has a comparatively high affinity for oxygen
Fetal myoglobin has a comparatively low affinity for oxygen
Most adaptations of the fetal circulatory system are designed to bypass the lungs and liver, which develop especially slowly. The ductus venosus shuttles blood directly from the umbilical vein to the inferior vena cava, avoiding the liver entirely. The foramen ovale is a right-to-left shunt between the atria that sends blood away from the right ventricle; the ductus arteriosus shunts the remaining blood from the right ventricle to the aorta to bypass the lungs. Finally, fetal hemoglobin has a high affinity for oxygen because it must compete with maternal blood in the placenta.
Fetal myoglobin does not have a low affinity for oxygen.
Example Question #907 : Biology
Hemoglobin is the principal oxygen-carrying protein in humans. It exists within erythrocytes, and binds up to four diatomic oxygen molecules simultaneously. Hemoglobin functions to maximize oxygen delivery to tissues, while simultaneously maximizing oxygen absorption in the lungs. Hemoglobin thus has a fundamentally contradictory set of goals. It must at once be opitimized to absorb oxygen, and to offload oxygen. Natural selection has overcome this apparent contradiction by making hemoglobin exquisitely sensitive to conditions in its microenvironment.
One way in which hemoglobin accomplishes its goals is through the phenomenon of cooperativity. Cooperativity refers to the ability of hemoglobin to change its oxygen binding behavior as a function of how many other oxygen atoms are bound to the molecule.
Fetal hemoglobin shows a similar pattern of cooperativity, but has unique binding characteristics relative to adult hemoglobin. Fetal hemoglobin reaches higher saturation at lower oxygen partial pressure.
Because of cooperativity, adult and fetal oxygen-hemoglobin dissociation curves appear as follows.
Beyond its ability to carry oxygen, hemoglobin is also effective as a blood buffer. The general reaction for the blood buffer system of hemoglobin is given below.
H+ + HbO2 ←→ H+Hb + O2
While most of the oxygen transported in blood is bound to hemoglobin, only a small fraction of carbon dioxide (CO2) present in blood is transported via this carrier. Most is dissolved in blood in an alternative form. Why does CO2 need to be changed to an alternative form to dissolve into blood?
CO2 is nonpolar, and blood is an aqueous solution
CO2 is polar, and blood is an aqueous solution
CO2 is polar, and needs to be modified to bind to carrier proteins like albumin
CO2 is nonpolar, and blood is not an aqueous solution
CO2 is polar, and blood is not an aqueous solution
CO2 is nonpolar, and blood is an aqueous solution
Carbon dioxide (CO2) is nonpolar, and thus can dissolve well only in nonpolar solvents. Since blood is an aqueous (and polar) solvent, CO2 needs to be converted to a polar form via blood enzymes to allow it to be dissolved directly in water.
Example Question #13 : Hemoglobin, Blood Cells, And Blood Proteins
Which of the following gases can bind to hemoglobin?
Hemoglobin can bind to all of these gases
Carbon monoxide (CO)
Oxygen (O2)
Carbon dioxide (CO2)
Hemoglobin can bind to all of these gases
Hemoglobin can bind to all three of these gases, however, it binds to each of them with a different affinity. Hemoglobin's affinity for the three gases, from highest to lowest, is listed below.
carbon monoxide (CO) > oxygen (O2) > carbon dioxide (CO2).
Note that cabron monoxide has the highest affininty; this is why is can be dangerous to inhale too much carbon monoxide, as it will displace onxygen that would otherwise bind to hemoglobin.
Example Question #14 : Hemoglobin, Blood Cells, And Blood Proteins
Carbonic anhydrase serves to convert carbon dioxide wastes, produced from cellular respiration, into bicarbonate. This bicarbonate buffers blood pH and allows for the transport of more carbon dioxide equivalents in the blood to the kidneys for excretion. The reaction catalyzed by carbonic anhydrase is:
How would running, as compared to walking, change the pH of the blood if breathing rate remains constant?
Decreased blood pH
The change cannot be determined without knowing more about the runner
Increased blood pH
Blood pH will remain the same
Decreased blood pH
Cellular respiration is more active during running than during walking, producing more carbon dioxide. The carbon dioxide will enter the carbonic anhydrase reaction, producing more protons in the blood and lowering the pH. To counter this drop in pH, runners will naturally increase their breathing rate. This serves to deliver more oxygen to the muscles, as well as to remove more carbon dioxide wastes and prevent acid from building in the blood.
Example Question #15 : Hemoglobin, Blood Cells, And Blood Proteins
Hemoglobin is the principal oxygen-carrying protein in humans. It exists within erythrocytes, and binds up to four diatomic oxygen molecules simultaneously. Hemoglobin functions to maximize oxygen delivery to tissues, while simultaneously maximizing oxygen absorption in the lungs. Hemoglobin thus has a fundamentally contradictory set of goals. It must at once be optimized to absorb oxygen, and to offload oxygen. Natural selection has overcome this apparent contradiction by making hemoglobin exquisitely sensitive to conditions in its microenvironment.
One way in which hemoglobin accomplishes its goals is through the phenomenon of cooperativity. Cooperativity refers to the ability of hemoglobin to change its oxygen binding behavior as a function of how many other oxygen atoms are bound to the molecule.
Fetal hemoglobin shows a similar pattern of cooperativity, but has unique binding characteristics relative to adult hemoglobin. Fetal hemoglobin reaches higher saturation at lower oxygen partial pressure.
Because of cooperativity, adult and fetal oxygen-hemoglobin dissociation curves appear as follows.
Beyond its ability to carry oxygen, hemoglobin is also effective as a blood buffer. The general reaction for the blood buffer system of hemoglobin is given below.
H+ + HbO2 ←→ H+Hb + O2
Considering the described oxygen affinity pattern for hemoglobin, which curve is likely to depict fetal hemoglobin?
Curve 1, as it shows greater affinity for oxygen
Curve 2, as it shows less affinity for oxygen
Cannot be determined from the information given
Curve 1, as it shows less affinity for oxygen
Curve 2, as it shows greater affinity for oxygen
Curve 1, as it shows greater affinity for oxygen
Curve 1 shows greater affinity for oxygen than curve 2, as it is higher up the y-axis at any single point on the x-axis. We would expect this finding for fetal hemoglobin, which would need to extract oxygen from maternal blood.
Example Question #16 : Hemoglobin, Blood Cells, And Blood Proteins
Hemoglobin is the principal oxygen-carrying protein in humans. It exists within erythrocytes, and binds up to four diatomic oxygen molecules simultaneously. Hemoglobin functions to maximize oxygen delivery to tissues, while simultaneously maximizing oxygen absorption in the lungs. Hemoglobin thus has a fundamentally contradictory set of goals. It must at once be optimized to absorb oxygen, and to offload oxygen. Natural selection has overcome this apparent contradiction by making hemoglobin exquisitely sensitive to conditions in its microenvironment.
One way in which hemoglobin accomplishes its goals is through the phenomenon of cooperativity. Cooperativity refers to the ability of hemoglobin to change its oxygen binding behavior as a function of how many other oxygen atoms are bound to the molecule.
Fetal hemoglobin shows a similar pattern of cooperativity, but has unique binding characteristics relative to adult hemoglobin. Fetal hemoglobin reaches higher saturation at lower oxygen partial pressure.
Because of cooperativity, adult and fetal oxygen-hemoglobin dissociation curves appear as follows.
Beyond its ability to carry oxygen, hemoglobin is also effective as a blood buffer. The general reaction for the blood buffer system of hemoglobin given below.
H+ + HbO2 ←→ H+Hb + O2
Hemoglobin is the most important component of red blood cells. How are red blood cells different from other cells of the body?
They lack a nucleus
They contain protein support for their membranes
They are larger than all other cells
They lack a cell membrane
They are produced in the thymus
They lack a nucleus
Red blood cells are unique in that they lack a nucleus and are functionally just "bags of hemoglobin." They are among the most specialized cells, doing little else but transporting oxygen in the blood.
The choice indicating protein support for the membrane may have also been tempting, and is true. This characteristic, however, is shared by other cells of the body. Also remember that red blood cells are produced by red bone marrow (and sometimes the liver), while certain white blood cells mature in the thymus.
Example Question #15 : Hemoglobin, Blood Cells, And Blood Proteins
Which of the following is a cause of alkalosis?
Increased parietal cell activity
High levels of 
Renal dysfunction leading to a buildup of urea and creatinine
Hyperventilation
Strenuous exercise leading to a buildup of lactate
Hyperventilation
Hyperventilation is a classic example of a process that can cause alkalosis, or basicity of the bloodstream. Hyperventilation can cause a net loss of CO2. Low levels of CO2 can cause respiratory alkalosis via reduction of carbonate in the blood. Lactate—also known as lactic acid—is a product of anaerobic respiration, and decreases blood pH. Increased levels of urea and creatinine indicate renal acidosis, a form of metabolic acidosis, which occurs when the kidney does not remove enough acid from the body.
Example Question #16 : Hemoglobin, Blood Cells, And Blood Proteins
A scientist takes a group of erythrocytes (red blood cells) and places them in a beaker containing a solution. The cells begin to shrink and eventually lyse. What can be concluded about the solution?
The solution contained albumin
The solution was isotonic to the erythrocytes
The solution was hypertonic to the erythrocytes
The solution was hypotonic to the erythrocytes
The solution contained bicarbonate
The solution was hypertonic to the erythrocytes
Placing erythrocytes in a hypertonic solution would cause them to shrink and burst, becuase water from the erythrocytes would move from high to low concenration (inside the cells to the outside hypertonic environment). Albumin and bicarbonate would have no effect, because they are normal components of blood. Placing them in a hypotonic solution would cause them to swell up.
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