3.2 Chapter 7 Levitzsky
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Questions and Answers

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?

  • 250 L/min
  • 83.3 L/min (correct)
  • 1000 L/min
  • 400 L/min

    • 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?

    <p>No, it is not sufficient</p> Signup and view all the answers

    During severe exercise, how much can the oxygen demand increase as compared to resting oxygen consumption?

    <p>Sixteen-fold</p> Signup and view all the answers

    What does Henry’s law state in relation to oxygen dissolved in plasma?

    <p>1 mL of plasma contains 0.00003 mL O2/mm Hg PO2 at 37°C</p> Signup and view all the answers

    Which component is necessary for the chemical reaction with oxygen to take place?

    <p>Both globin and heme in proper spatial orientation</p> Signup and view all the answers

    Which type of hemoglobin has a higher affinity for oxygen than adult hemoglobin?

    <p>Fetal hemoglobin (HbF)</p> Signup and view all the answers

    How many iron atoms are there in each heme group?

    <p>1</p> Signup and view all the answers

    What does methemoglobin contain that limits its capacity to bind oxygen?

    <p>Iron atom in the ferric state</p> Signup and view all the answers

    What is the oxygen-carrying capacity of hemoglobin per gram?

    <p>1.34 mL</p> Signup and view all the answers

    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?

    <p>26.8 mL</p> Signup and view all the answers

    What determines the amount of oxygen that binds to hemoglobin in erythrocytes?

    <p>PO2 of the plasma</p> Signup and view all the answers

    What does 'percent saturation' in hemoglobin represent?

    <p>Percentage of hemoglobin bound to oxygen</p> Signup and view all the answers

    Why is the oxyhemoglobin dissociation curve S-shaped and not linear?

    <p>It is a result of positive cooperativity between hemoglobin subunits</p> Signup and view all the answers

    How does the dissociation curve for a single monomer of hemoglobin compare to that for the tetramer?

    <p>Single monomer curve is steeper than the tetramer curve</p> Signup and view all the answers

    'Oxygen content' in blood is influenced by which factors?

    <p>Hemoglobin concentration and PO2 in the plasma</p> Signup and view all the answers

    What is the influence of pH and PCO2 on the oxyhemoglobin dissociation curve referred to as?

    <p>Bohr effect</p> Signup and view all the answers

    How does high blood temperature affect the oxyhemoglobin dissociation curve?

    <p>Shifts it to the right</p> Signup and view all the answers

    What happens to the oxyhemoglobin dissociation curve at very low blood temperatures?

    <p>It shifts to the left</p> Signup and view all the answers

    What is the role of 2,3-BPG in hemoglobin's affinity for oxygen?

    <p>Decreases affinity for oxygen</p> Signup and view all the answers

    During chronic hypoxic conditions, what happens to the oxyhemoglobin dissociation curve due to 2,3-BPG production?

    <p>Shifts to the right</p> Signup and view all the answers

    Why is it important to restore normal levels of 2,3-BPG in banked blood before transfusion?

    <p>To decrease oxygen unloading</p> Signup and view all the answers

    What happens to the P50 value of normal human blood if the oxyhemoglobin dissociation curve is shifted to the right?

    <p>Increases</p> Signup and view all the answers

    How does carbon monoxide affect the oxyhemoglobin dissociation curve?

    <p>Shifts it to the left</p> Signup and view all the answers

    How do low pH, high PCO2, increased 2,3-BPG, and higher temperature collectively affect the oxyhemoglobin dissociation curve?

    <p>Shift it to the right</p> Signup and view all the answers

    In what way does anemia secondary to blood loss affect oxygen transport in the body?

    <p>Reduces arterial PO2</p> Signup and view all the answers

    What is the effect of pH, PCO2, and temperature on enhancing or interfering with oxygen unloading?

    <p>More pronounced at lower PO2s</p> Signup and view all the answers

    What happens to the oxyhemoglobin dissociation curve when venous blood returns to the lung and CO2 leaves the blood?

    <p>Shifts to the left</p> Signup and view all the answers

    Which of the following is a common cause of methemoglobin?

    <p>Nitrite poisoning</p> Signup and view all the answers

    What is the effect of iron atoms in the Fe3+ state on oxygen?

    <p>They do not combine with oxygen</p> Signup and view all the answers

    How does fetal hemoglobin's affinity for oxygen compare to that of maternal hemoglobin?

    <p>Fetal hemoglobin has higher affinity for oxygen</p> Signup and view all the answers

    In what way does myoglobin differ from normal adult hemoglobin?

    <p>It binds more oxygen at higher partial pressures</p> Signup and view all the answers

    Which of the following statements describes the dissociation curve of myoglobin compared to normal adult hemoglobin?

    <p>Myoglobin's dissociation curve is far to the left of normal adult hemoglobin</p> Signup and view all the answers

    How do abnormal hemoglobins typically affect their affinity for oxygen?

    <p>They usually decrease their affinity for oxygen</p> Signup and view all the answers

    At a PO2 of 40 mm Hg, hemoglobin is approximately what percentage saturated with oxygen?

    <p>75%</p> Signup and view all the answers

    What happens to the oxyhemoglobin dissociation curve when the PO2 is greater than approximately 70 mm Hg?

    <p>It flattens out</p> Signup and view all the answers

    What effect does elevated levels of 2,3-BPG have on the oxyhemoglobin dissociation curve?

    <p>Shifts it to the right</p> Signup and view all the answers

    How does a high pH affect the oxyhemoglobin dissociation curve?

    <p>Shifts it to the left</p> Signup and view all the answers

    'Shifting the oxyhemoglobin dissociation curve to the right' indicates what in terms of oxygen binding?

    <p>Decreased affinity for oxygen</p> Signup and view all the answers

    At what partial pressure of CO2 (PCO2) in mm Hg does the arterial blood carry about 5% of the carbon dioxide in physical solution?

    <p>40</p> Signup and view all the answers

    What chemical compounds are formed when carbon dioxide combines with the terminal amine groups in blood proteins?

    <p>Carbamino compounds</p> Signup and view all the answers

    What happens when a carbamino compound is formed in blood proteins?

    <p>A hydrogen ion is released</p> Signup and view all the answers

    What is the primary role of hydrogen ions in the context of hemoglobin and oxygen transport?

    <p>Facilitating the release of oxygen from hemoglobin</p> Signup and view all the answers

    How is electrical neutrality maintained in erythrocytes during the exchange of ions?

    <p>Through the exchange of chloride ions for bicarbonate ions</p> Signup and view all the answers

    What happens to bicarbonate ions as the PO2 increases and the PCO2 decreases in the lungs?

    <p>They diffuse out of the red blood cells</p> Signup and view all the answers

    During oxygen release, what is the role of hydrogen ions in combination with bicarbonate ions?

    <p>Conversion into carbon dioxide</p> Signup and view all the answers

    In the context of hemoglobin and oxygen transport, what is the purpose of the chloride shift?

    <p>Maintain electrical neutrality in tissues</p> Signup and view all the answers

    What is the main protein in the blood that transports carbon dioxide?

    <p>Globin of hemoglobin</p> Signup and view all the answers

    How is most of the carbon dioxide transported in the blood?

    <p>Bound to amino acids of hemoglobin</p> Signup and view all the answers

    Which enzyme plays a crucial role in the conversion of carbon dioxide to bicarbonate ions?

    <p>Carbonic anhydrase</p> Signup and view all the answers

    What allows hemoglobin to accept hydrogen ions and continue the reaction during carbon dioxide transport?

    <p>Hemoglobin's ability to bind oxygen</p> Signup and view all the answers

    In the carbon dioxide dissociation curve for whole blood, how does it compare to the oxygen dissociation curve?

    <p>It has a steeper slope</p> Signup and view all the answers

    What effect does deoxyhemoglobin have on the pH and PCO2 levels during oxygen transport?

    <p>Decreases pH and PCO2 levels</p> Signup and view all the answers

    How does deoxyhemoglobin affect oxygen binding at low pHs or high PCO2s?

    <p>It decreases oxygen binding</p> Signup and view all the answers

    What allows more carbon dioxide to be transported in bicarbonate ion form by deoxyhemoglobin?

    <p>Higher affinity for hydrogen ions than oxyhemoglobin.</p> Signup and view all the answers

    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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