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Example Question #1 : Hemoglobin, Blood Cells, And Blood Proteins
Bilirubin is a byproduct of heme catabolism, and is excreted in the bile and stool. Bilirubin is likely derived from processes in what cell type?
Adipocytes
Epithelial cells
Red blood cells
Enterocytes
Red blood cells
Heme is an important functional group of hemoglobin. Bilirubin, which is a byproduct of heme breakdown, comes from red blood cells. The liver receives unconjugated bilirubin from the blood and conjugates it via phase II metabolism to make it more soluble for excretion via the bile and stool. Fat cells (adipocytes), skin cells (epithelial cells), and small intestine absorptive cells (enterocytes) do not contain heme to be processed into bilirubin.
Example Question #1 : Hemoglobin, Blood Cells, And Blood Proteins
A fetus does not breathe inside the womb, and so it must obtain oxygen a different way. What property of hemoglobin allows a fetus to recieve the oxyge it needs to develop?
The partial pressure of oxygen in fetal hemoglobin is always higher than that of its mother.
Fetal hemoglobin has a lower affinity for oxygen than adult hemoglobin.
Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin.
The partial pressure of oxygen in fetal hemoglobin is always the same as that of its mother.
Fetal hemoglobin is composed of four subunits while adult hemoglobin is composed of two.
Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin.
Fetal hemoglobin has a higher affinity for oxygen that adult hemoglobin. Maternal and Fetal blood never mix during pregnancy, but they come close to each other in the placenta. Oxygen diffuses easily to fetal hemoglobin here. The reason fetal hemoglobin has a higher affinity is it is composed of two alpha and two gamma subunits, while adult hemoglobin is composed of two alpha and two beta subunits.
Example Question #1 : Hemoglobin, Blood Cells, And Blood Proteins
Which factors contribute to the Bohr Effect?
Low pH, high CO2, low temperature
High pH, low CO2
Low pH, low CO2
Low pH, high CO2
Low pH, high CO2, high temperature
Low pH, high CO2
The Bohr Effect describes hemoglobin's affinty for oxygen as a function of blood pH and carbon dioxide content. An increase in CO2 concentration will lower the blood pH, causing the hemoglobin affinity for oxygen to reduce. High temperature also causes oxygen to be released from hemoglobin, but is not related to the Bohr Effect.
Think about when you're exercising. Your blood has a reduced O2 concentration and an elevated CO2 concentration. These factors allow hemoglobin to release more oxygen in the muscles to faciliate ATP production and maintain energy levels.
Example Question #1 : 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 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
Myoglobin is a similar carrier molecule to hemoglobin, but it only has one site of oxygen binding instead of four. Which characteristic of hemoglobin is most likely not shared by myoglobin?
Peptide nature
Cooperativity
Iron-binding capacity
Ability to reversibly bind oxygen
Level of solubility
Cooperativity
Cooperativity, as defined in the passage, requires more than one binding site. Without more than one binding site, it is impossible for a carrier to change its affinity for additional cargo after the first piece is either loaded or unloaded. That additional cargo simply doesn't exist for myoglobin.
Example Question #2 : Hemoglobin, Blood Cells, And Blood Proteins
Which of the following gases can be bound by hemoglobin?
Oxygen
Carbon dioxide
All of the answers are correct
Carbon monoxide
All of the answers are correct
All of these gases can be bound by hemoglobin. Hemoglobin transports oxygen from the lungs to the necessary tissue, and carbon dioxide from the tissue to the lungs. Hemoglobin has a much higher affinity for carbon monoxide than oxygen, which is why it is so dangerous to inhale carbon monoxide.
Example Question #1 : Hemoglobin, Blood Cells, And Blood Proteins
Which of the following is most likely to decrease oxygen's affinity to hemoglobin in the bloodstream?
Low pH
High pH
Low temperature
Low levels of carbon dioxide
Low pH
High levels of carbon dioxide (CO2), low pH, and high temperatures all act to decrease oxygen's affinity toward human hemoglobin. Think of working muscle, which produces hot, acidic, high CO2 conditions in the blood; in this environment, it is important for hemoglobin to release transported oxygen to provide an aerobic environment to the muscle.
Example Question #71 : Circulatory System
If an individual's blood has a slightly lower pH than normal, this means that oxygen affinity to hemoglobin __________.
increases
remains the same because only carbon dioxide levels can affect affinity
remains the same because only oxygen levels can affect affinity
decreases
remains the same because only temperature can affect affinity
decreases
A decrease in pH is generally caused by an increase in carbon dioxide in the blood, and will cause hemoglobin to have a lower affinity to oxygen. This makes sense, because we want to easily release oxygen to tissues with high levels of carbon dioxide, and quickly bind and remove the carbon dioxide from the cells to the lungs for expiration from the body.
Increased temperature will also decrease the affinity of hemoglobin for oxygen.
Example Question #1 : Hemoglobin, Blood Cells, And Blood Proteins
Hemoglobin is the protein responsible for the transport of oxygen throughout the bloodstream. The saturation of hemoglobin can be graphed based on the pressure of oxygen. As the pressure of oxygen increases, the saturation of hemoglobin with oxygen will increase in a sigmoidal fashion. This oxygen dissociation curve can be shifted depending on the external conditions in the blood.
Which of the following factors will not decrease the dissociation curve between oxygen and hemoglobin?
An increase in carbon dioxide pressure
A decrease in pH
An increase in temperature
The partial pressure of oxygen
The partial pressure of oxygen
The oxygen dissociation curve is a graph of hemoglobin saturation versus oxygen partial pressure. As oxygen partial pressure increases, hemoglobin will generally be more saturated. The oxygen partial pressure will affect the saturation percentage of hemoglobin in the blood, but will not shift the curve itself. All other options will shift the oxygen dissociation curve to the right, lowering hemoglobin's affinity for oxygen.
Example Question #71 : Circulatory System
Hemoglobin displays a property whereby binding of one oxygen molecule decreases the resistance of the hemoglobin molecule to additional oxygen binding. This property of hemoglobin is known as __________.
cooperativity
coordination
oxygen shift
resistance
cooperativity
Hemoglobin displays the unique property of cooperativity, meaning that once one molecule of oxygen has bound to the hemoglobin molecule, adding the three next molecules is easier. This gives the hemoglobin binding curve the typical sigmoidal oxygen dissociation curve.
Cooperativity helps hemoglobin bind four oxygen molecules in the lungs and maintain the bonds until it enters a region of very low oxygen partial pressure. The most energy is required to remove the first oxygen; the next three are easier because the cooperativity has been lessened. As hemoglobin travels, it is able to selectively distribute oxygen the areas of the body that need it most because of this property.
Example Question #2 : Hemoglobin, Blood Cells, And Blood Proteins
Which of the following scenarios will cause the oxygen-hemoglobin dissociation curve to shift to the left?
Exercise
Decreased pH
Increased 2,3-bisphosphoglycerate
Fever
Hyperventilation
Hyperventilation
Hemoglobin's affinity for oxygen can vary based upon the environment. A right shift, which lowers hemoglobin's affinity for oxygen, occurs when there is a need for oxygen to be released to surrounding tissue. This occurs during exercise, increased temperatures, increased 2,3-bisphosphglycerate, increased carbon dioxide, and decreased pH.
Hyperventilation will increase oxygen and decrease carbon dioxide, which will effectively cause a left shift. Left shifts occur under circumstances opposite from the right shift. A decrease in temperature, 2,3-bisphosphoglycerate, or carbon dioxide will cause a left shift.
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