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Questions and Answers
What is the approximate oxygen content in normal arterial blood with a PO2 of 100 mm Hg?
What is the approximate oxygen content in normal arterial blood with a PO2 of 100 mm Hg?
- 0.3 mL O2/mL of blood
- 0.003 mL O2/mL of blood (correct)
- 0.00003 mL O2/mL of blood
- 3 mL O2/mL of blood
What would the cardiac output need to be if the tissues were able to remove the entire 0.3 mL O2/100 mL of blood flow they receive?
What would the cardiac output need to be if the tissues were able to remove the entire 0.3 mL O2/100 mL of blood flow they receive?
- 250 L/min
- 83.3 L/min (correct)
- 1000 L/min
- 400 L/min
What is the resting oxygen consumption of an adult approximately?
What is the resting oxygen consumption of an adult approximately?
- 100 mL O2/min
- 500 mL O2/min
- 250 to 300 mL O2/min (correct)
- 350 to 400 mL O2/min
At normal FIO2 and barometric pressure, is the physically dissolved oxygen in the blood sufficient to fulfill the body’s oxygen demand?
At normal FIO2 and barometric pressure, is the physically dissolved oxygen in the blood sufficient to fulfill the body’s oxygen demand?
During severe exercise, how much can the oxygen demand increase as compared to resting oxygen consumption?
During severe exercise, how much can the oxygen demand increase as compared to resting oxygen consumption?
What does Henry’s law state in relation to oxygen dissolved in plasma?
What does Henry’s law state in relation to oxygen dissolved in plasma?
Which component is necessary for the chemical reaction with oxygen to take place?
Which component is necessary for the chemical reaction with oxygen to take place?
Which type of hemoglobin has a higher affinity for oxygen than adult hemoglobin?
Which type of hemoglobin has a higher affinity for oxygen than adult hemoglobin?
How many iron atoms are there in each heme group?
How many iron atoms are there in each heme group?
What does methemoglobin contain that limits its capacity to bind oxygen?
What does methemoglobin contain that limits its capacity to bind oxygen?
What is the oxygen-carrying capacity of hemoglobin per gram?
What is the oxygen-carrying capacity of hemoglobin per gram?
If a person has 20 g Hb/100 mL of blood, what would be their oxygen-carrying capacity in mL O2/100 mL of blood?
If a person has 20 g Hb/100 mL of blood, what would be their oxygen-carrying capacity in mL O2/100 mL of blood?
What determines the amount of oxygen that binds to hemoglobin in erythrocytes?
What determines the amount of oxygen that binds to hemoglobin in erythrocytes?
What does 'percent saturation' in hemoglobin represent?
What does 'percent saturation' in hemoglobin represent?
Why is the oxyhemoglobin dissociation curve S-shaped and not linear?
Why is the oxyhemoglobin dissociation curve S-shaped and not linear?
How does the dissociation curve for a single monomer of hemoglobin compare to that for the tetramer?
How does the dissociation curve for a single monomer of hemoglobin compare to that for the tetramer?
'Oxygen content' in blood is influenced by which factors?
'Oxygen content' in blood is influenced by which factors?
What is the influence of pH and PCO2 on the oxyhemoglobin dissociation curve referred to as?
What is the influence of pH and PCO2 on the oxyhemoglobin dissociation curve referred to as?
How does high blood temperature affect the oxyhemoglobin dissociation curve?
How does high blood temperature affect the oxyhemoglobin dissociation curve?
What happens to the oxyhemoglobin dissociation curve at very low blood temperatures?
What happens to the oxyhemoglobin dissociation curve at very low blood temperatures?
What is the role of 2,3-BPG in hemoglobin's affinity for oxygen?
What is the role of 2,3-BPG in hemoglobin's affinity for oxygen?
During chronic hypoxic conditions, what happens to the oxyhemoglobin dissociation curve due to 2,3-BPG production?
During chronic hypoxic conditions, what happens to the oxyhemoglobin dissociation curve due to 2,3-BPG production?
Why is it important to restore normal levels of 2,3-BPG in banked blood before transfusion?
Why is it important to restore normal levels of 2,3-BPG in banked blood before transfusion?
What happens to the P50 value of normal human blood if the oxyhemoglobin dissociation curve is shifted to the right?
What happens to the P50 value of normal human blood if the oxyhemoglobin dissociation curve is shifted to the right?
How does carbon monoxide affect the oxyhemoglobin dissociation curve?
How does carbon monoxide affect the oxyhemoglobin dissociation curve?
How do low pH, high PCO2, increased 2,3-BPG, and higher temperature collectively affect the oxyhemoglobin dissociation curve?
How do low pH, high PCO2, increased 2,3-BPG, and higher temperature collectively affect the oxyhemoglobin dissociation curve?
In what way does anemia secondary to blood loss affect oxygen transport in the body?
In what way does anemia secondary to blood loss affect oxygen transport in the body?
What is the effect of pH, PCO2, and temperature on enhancing or interfering with oxygen unloading?
What is the effect of pH, PCO2, and temperature on enhancing or interfering with oxygen unloading?
What happens to the oxyhemoglobin dissociation curve when venous blood returns to the lung and CO2 leaves the blood?
What happens to the oxyhemoglobin dissociation curve when venous blood returns to the lung and CO2 leaves the blood?
Which of the following is a common cause of methemoglobin?
Which of the following is a common cause of methemoglobin?
What is the effect of iron atoms in the Fe3+ state on oxygen?
What is the effect of iron atoms in the Fe3+ state on oxygen?
How does fetal hemoglobin's affinity for oxygen compare to that of maternal hemoglobin?
How does fetal hemoglobin's affinity for oxygen compare to that of maternal hemoglobin?
In what way does myoglobin differ from normal adult hemoglobin?
In what way does myoglobin differ from normal adult hemoglobin?
Which of the following statements describes the dissociation curve of myoglobin compared to normal adult hemoglobin?
Which of the following statements describes the dissociation curve of myoglobin compared to normal adult hemoglobin?
How do abnormal hemoglobins typically affect their affinity for oxygen?
How do abnormal hemoglobins typically affect their affinity for oxygen?
At a PO2 of 40 mm Hg, hemoglobin is approximately what percentage saturated with oxygen?
At a PO2 of 40 mm Hg, hemoglobin is approximately what percentage saturated with oxygen?
What happens to the oxyhemoglobin dissociation curve when the PO2 is greater than approximately 70 mm Hg?
What happens to the oxyhemoglobin dissociation curve when the PO2 is greater than approximately 70 mm Hg?
What effect does elevated levels of 2,3-BPG have on the oxyhemoglobin dissociation curve?
What effect does elevated levels of 2,3-BPG have on the oxyhemoglobin dissociation curve?
How does a high pH affect the oxyhemoglobin dissociation curve?
How does a high pH affect the oxyhemoglobin dissociation curve?
'Shifting the oxyhemoglobin dissociation curve to the right' indicates what in terms of oxygen binding?
'Shifting the oxyhemoglobin dissociation curve to the right' indicates what in terms of oxygen binding?
At what partial pressure of CO2 (PCO2) in mm Hg does the arterial blood carry about 5% of the carbon dioxide in physical solution?
At what partial pressure of CO2 (PCO2) in mm Hg does the arterial blood carry about 5% of the carbon dioxide in physical solution?
What chemical compounds are formed when carbon dioxide combines with the terminal amine groups in blood proteins?
What chemical compounds are formed when carbon dioxide combines with the terminal amine groups in blood proteins?
What happens when a carbamino compound is formed in blood proteins?
What happens when a carbamino compound is formed in blood proteins?
What is the primary role of hydrogen ions in the context of hemoglobin and oxygen transport?
What is the primary role of hydrogen ions in the context of hemoglobin and oxygen transport?
How is electrical neutrality maintained in erythrocytes during the exchange of ions?
How is electrical neutrality maintained in erythrocytes during the exchange of ions?
What happens to bicarbonate ions as the PO2 increases and the PCO2 decreases in the lungs?
What happens to bicarbonate ions as the PO2 increases and the PCO2 decreases in the lungs?
During oxygen release, what is the role of hydrogen ions in combination with bicarbonate ions?
During oxygen release, what is the role of hydrogen ions in combination with bicarbonate ions?
In the context of hemoglobin and oxygen transport, what is the purpose of the chloride shift?
In the context of hemoglobin and oxygen transport, what is the purpose of the chloride shift?
What is the main protein in the blood that transports carbon dioxide?
What is the main protein in the blood that transports carbon dioxide?
How is most of the carbon dioxide transported in the blood?
How is most of the carbon dioxide transported in the blood?
Which enzyme plays a crucial role in the conversion of carbon dioxide to bicarbonate ions?
Which enzyme plays a crucial role in the conversion of carbon dioxide to bicarbonate ions?
What allows hemoglobin to accept hydrogen ions and continue the reaction during carbon dioxide transport?
What allows hemoglobin to accept hydrogen ions and continue the reaction during carbon dioxide transport?
In the carbon dioxide dissociation curve for whole blood, how does it compare to the oxygen dissociation curve?
In the carbon dioxide dissociation curve for whole blood, how does it compare to the oxygen dissociation curve?
What effect does deoxyhemoglobin have on the pH and PCO2 levels during oxygen transport?
What effect does deoxyhemoglobin have on the pH and PCO2 levels during oxygen transport?
How does deoxyhemoglobin affect oxygen binding at low pHs or high PCO2s?
How does deoxyhemoglobin affect oxygen binding at low pHs or high PCO2s?
What allows more carbon dioxide to be transported in bicarbonate ion form by deoxyhemoglobin?
What allows more carbon dioxide to be transported in bicarbonate ion form by deoxyhemoglobin?
Study Notes
Transport of Oxygen and Carbon Dioxide
- Physically dissolved oxygen in the blood is not sufficient to meet the body's oxygen demand, even at rest.
- The oxygen physically dissolved in the blood is about 0.003 mL O2/mL of blood, or 0.3 mL O2/100 mL of blood.
Structure of Hemoglobin
- Hemoglobin is a complex molecule with a molecular weight of about 64,500.
- It has a tetrameric structure consisting of four linked polypeptide chains, each attached to a protoporphyrin (heme) group.
- Each heme group has a ferrous (Fe2+) iron atom at its center, which binds to oxygen.
- Each of the four polypeptide chains can bind a molecule of oxygen (or carbon monoxide).
- The tetrameric hemoglobin molecule can combine chemically with four oxygen molecules (or eight oxygen atoms).
Chemical Reaction of Oxygen and Hemoglobin
- Hemoglobin rapidly combines reversibly with oxygen.
- The reaction is very fast, with a half-time of 0.01 seconds or less.
- Each gram of hemoglobin is capable of combining with about 1.39 mL of oxygen under optimal conditions.
- The oxygen-carrying capacity of hemoglobin is conventionally considered to be 1.34 mL O2/g Hb.
Oxyhemoglobin Dissociation Curve
- The oxyhemoglobin dissociation curve is a plot of the percentage of hemoglobin saturated with oxygen against the PO2 of the plasma.
- The curve is S-shaped, steep at lower PO2s and nearly flat when the PO2 is above 70 mm Hg.
- The curve is influenced by the availability of one of the reactants, oxygen (expressed as the PO2 of the plasma).
Loading Oxygen in the Lungs
- Mixed venous blood entering the pulmonary capillaries normally has a PO2 of about 40 mm Hg.
- At a PO2 of 40 mm Hg, hemoglobin is about 75% saturated with oxygen.
- The oxyhemoglobin dissociation curve is relatively flat when PO2 is greater than approximately 70 mm Hg.
Unloading Oxygen at the Tissues
- The PO2 in the capillaries varies from tissue to tissue, being very low in some (e.g., myocardium) and relatively higher in others (e.g., kidney).
- A small decrease in PO2 can result in a substantial further dissociation of oxygen and hemoglobin, unloading more oxygen for use by the tissues.
Influences on the Oxyhemoglobin Dissociation Curve
- High temperature, low pH, high PCO2, and elevated levels of 2,3-BPG all shift the oxyhemoglobin dissociation curve to the right.
- Effects of pH and PCO2 on the oxyhemoglobin dissociation curve are referred to as the Bohr effect.
- High temperatures shift the curve to the right; low temperatures shift the curve to the left.
- 2,3-BPG binds to hemoglobin in erythrocytes, decreasing the affinity of hemoglobin for oxygen.### Factors Affecting Oxygen Transport
- pH of 7.4, temperature of 37°C, P50 of 26-27 mmHg for normal human blood
- P50 increases when oxyhemoglobin dissociation curve shifts to the right
- P50 decreases when oxyhemoglobin dissociation curve shifts to the left
Anemia's Effect on Oxygen Transport
- Most forms of anemia do not affect oxyhemoglobin dissociation curve
- Anemia decreases amount of hemoglobin, but not percent saturation or arterial PO2
- Arterial oxygen content is reduced due to decreased hemoglobin
Carbon Monoxide's Effect on Oxygen Transport
- Carbon monoxide has a higher affinity for hemoglobin than oxygen
- Carbon monoxide shifts oxyhemoglobin dissociation curve to the left
- Carbon monoxide can prevent loading of oxygen in the lungs and unloading of oxygen at tissues
Nitric Oxide's Effect on Oxygen Transport
- Nitric oxide reacts with oxyhemoglobin to form methemoglobin and nitrate
- Nitric oxide can react with deoxyhemoglobin to form a hemoglobin-nitric oxide complex
- Nitric oxide may play a role in hypoxia-induced vasodilation
Methemoglobin
- Hemoglobin with iron in the ferric (Fe3+) state
- Does not combine with oxygen
- Can be caused by nitrite poisoning, oxidant drugs, or congenital hemoglobin M
Other Hemoglobins
- Fetal hemoglobin (HbF) has a higher affinity for oxygen than adult hemoglobin (HbA)
- Abnormal hemoglobins can have increased or decreased affinities for oxygen
Myoglobin
- A heme protein found in muscle cells
- Can combine with a single molecule of oxygen
- Has a hyperbolic dissociation curve far to the left of HbA
- Can store and transport oxygen in skeletal muscle
Artificial Blood
- Fluorocarbon emulsions can carry oxygen reversibly
- Can carry significantly more oxygen than plasma
- May be useful as emergency blood substitutes, for transfusions, and in anemic patients or during surgery
Cyanosis
- A sign of poor oxygen transport
- Occurs when more than 5 g Hb/100 mL of arterial blood is in the deoxy state
- Can appear bluish-purple discoloration of skin, nail beds, and mucous membranes
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