Gas Transport and Exchange in Blood
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Questions and Answers

What percentage of oxygen is dissolved in blood plasma?

  • 10%
  • 98.5%
  • 1.5% (correct)
  • 50%

    • Carbon dioxide has a higher solubility in plasma compared to oxygen.

    True

    What are the three states in which gases can be transported in the blood?

    Dissolved in plasma, chemically combined with hemoglobin, converted to a different molecule.

    The primary function of red blood cells in gas transport is to remove __________ from the plasma.

    <p>O2 and CO2</p> Signup and view all the answers

    Match the gas with its corresponding pressure in the tissues:

    <p>O2 = 40 mm Hg CO2 = 46 mm Hg</p> Signup and view all the answers

    What drives the passive diffusion of gases during gas exchange?

    <p>Pressure gradients</p> Signup and view all the answers

    Hemoglobin only temporarily binds to oxygen and carbon dioxide.

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

    At what pressure (in mmHg) does oxygen move from the alveoli into the pulmonary capillaries?

    <p>104 mm Hg</p> Signup and view all the answers

    What percentage of oxygen is released from hemoglobin at the tissues during normal activity?

    <p>25%</p> Signup and view all the answers

    Higher temperature decreases hemoglobin's ability to bind oxygen.

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

    What is the primary way carbon dioxide is transported in the bloodstream?

    <p>As bicarbonate ions (HCO3−)</p> Signup and view all the answers

    What happens to oxygen when the partial pressure of O2 (PO2) increases?

    <p>Oxygen binds to hemoglobin.</p> Signup and view all the answers

    The process of CO2 combining with water to form carbonic acid is catalyzed by __________.

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

    Hemoglobin is 100% saturated with oxygen at a PO2 of 100 mm Hg.

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

    Match each factor with its effect on hemoglobin's ability to bind oxygen:

    <p>Blood pH = Decreases binding ability Temperature = Decreases binding ability 2,3 Bisphosphoglycerate concentration = Decreases binding ability Partial pressure of Carbon Dioxide = Decreases binding ability</p> Signup and view all the answers

    Which of the following contributes to the release of oxygen from hemoglobin?

    <p>High Partial pressure of Carbon Dioxide</p> Signup and view all the answers

    What occurs in the tissue capillaries regarding oxygen transport?

    <p>Oxygen is released from hemoglobin.</p> Signup and view all the answers

    Only 7% of carbon dioxide travels in the bloodstream dissolved directly in plasma.

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

    At a low PO2, hemoglobin has a saturation level of _____%.

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

    What is formed when carbon dioxide reacts with hemoglobin?

    <p>Carbaminohemoglobin (HbCO2)</p> Signup and view all the answers

    How does cooperative binding affect hemoglobin's affinity for O2?

    <p>Affinity increases as saturation increases.</p> Signup and view all the answers

    Match the following PO2 values with their corresponding hemoglobin saturation levels:

    <p>100 mm Hg = 98% saturated 40 mm Hg = 75% saturated 0 mm Hg = 0% saturated 60 mm Hg = 90% saturated</p> Signup and view all the answers

    At high PO2 levels, hemoglobin releases more O2 to tissues.

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

    What shape does the oxygen-hemoglobin dissociation curve take?

    <p>Sigmoid or S-shaped</p> Signup and view all the answers

    What is the primary function of the chloride shift in red blood cells?

    <p>To maintain a neutral charge within the RBC membrane</p> Signup and view all the answers

    93% of carbon dioxide is transported in the bloodstream dissolved in plasma.

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

    What is carbaminohemoglobin?

    <p>Hemoglobin bound to carbon dioxide</p> Signup and view all the answers

    The process of converting CO2 to H2CO3 is facilitated by __________.

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

    Match the following components related to gas transport with their respective functions:

    <p>HCO3− = Moves out of RBC in exchange for Cl− CO2 = Binds to hemoglobin to form carbaminohemoglobin Hb = Buffer for H+ ions Cl− = Enters RBC during the chloride shift</p> Signup and view all the answers

    Which percentage of carbon dioxide is transported as bicarbonate (HCO3−)?

    <p>70%</p> Signup and view all the answers

    The dissociation curve of oxygen-Hb indicates that hemoglobin saturates with oxygen under high pressure of oxygen.

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

    Name two ways in which oxygen is transported in the bloodstream.

    <p>Bound to hemoglobin and dissolved in plasma</p> Signup and view all the answers

    Study Notes

    Gas Transport

    • Blood transports oxygen (O2) and carbon dioxide (CO2) between the lungs and tissues.
    • Gases are transported:
      • Dissolved in plasma
      • Chemically combined with hemoglobin
      • Converted to a different molecule
    • Red blood cells (RBCs) are crucial for gas transport because gases have limited solubility in plasma.
    • RBCs remove O2 and CO2 from plasma, bind them, or transform them into another molecule.
    • This allows more O2 and CO2 to diffuse into the blood and be transported.
    • Reactions between gases and RBCs are temporary and reversible.
    • When plasma O2 and CO2 concentrations decline, RBCs release bound O2 and CO2.

    Gas Exchange

    • Gas exchange between lungs, RBCs, and tissues occurs passively by diffusion, driven by pressure gradients.
    • PO2 is higher in alveoli (~100 mm Hg) than in pulmonary capillaries (~40 mm Hg).
    • This gradient drives O2 movement into pulmonary capillaries.
    • PCO2 is higher in pulmonary capillaries (~46 mm Hg) than in alveoli (~40 mm Hg).
    • This gradient drives CO2 movement into alveoli.
    • Pressure differences cause gas diffusion from high to low pressure.

    Oxygen Transport

    • Blood plasma cannot transport enough O2 to meet physiological needs due to its low solubility.
    • Only 1.5% of oxygen dissolves in plasma, with 98.5% combining with hemoglobin (Hb) in RBCs.
    • This combination is loose and reversible.
    • Increased PO2 causes O2 to combine with Hb (pulmonary capillaries).
    • Decreased PO2 causes O2 to be released from Hb (tissue capillaries).
    • Oxygen in blood either:
      • Remains as dissolved oxygen in plasma.
      • Binds to Hb to form oxyhemoglobin (HbO2).

    Oxygen-Hemoglobin Dissociation Curve

    • The curve describes the percentage saturation of Hb in blood at different blood PO2 values.
    • It represents the reversible binding and dissociation of oxygen to hemoglobin: Hb + O2 ↔ HbO2
    • Hb is 100% saturated with O2 when four O2 molecules bind to the four heme groups in a Hb molecule.
    • At a PO2 of 100 mm Hg (blood leaving pulmonary capillaries), Hb is 98% saturated.
    • At a PO2 of 40 mm Hg (blood leaving tissue capillaries), Hb is 75% saturated.
    • Only 23% of the oxygen picked up in the lungs is released at the tissues (the remaining 75% remains bound to Hb).

    Factors Affecting Hb Saturation

    • Blood pH (carbonic acid, lactic acid)
    • Temperature
    • 2,3 Bisphosphoglycerate concentration (2,3 BPG)
    • Partial pressure of Carbon Dioxide (PCO2)
    • These factors either directly or indirectly alter Hb structure, decreasing its ability to bind oxygen and causing oxygen release.

    Carbon Dioxide Transport

    • CO2 is produced by cells throughout the body as a by-product of metabolism.
    • CO2 diffuses from tissue cells into capillary blood and is transported in three ways:
      • 7% dissolves in plasma.
      • 93% diffuses into RBCs: Some combine with Hb to form carbaminohemoglobin (HbCO2) or is converted to carbonic acid.
    • Carbonic acid (H2CO3) easily dissociates into H+ ions and bicarbonate ions.

    Carbaminohemoglobin

    • 23% of CO2 is carried and stored in blood by Hb molecules.
    • CO2 attaches to an exposed amino group (-NH) of the Hb molecule to form carbaminohemoglobin = HbCO2.

    Carbonic Acid Formation

    • 70% of CO2 is transported as carbonic acid (H2CO3).
    • Within RBCs, CO2 combines with water, and through the activity of the enzyme carbonic anhydrase transforms into carbonic acid (H2CO3).
    • H2CO3 dissociates into H+ and bicarbonate (HCO3-).
    • CO2 travels in the bloodstream primarily as HCO3-.
    • H+ is removed by binding to Hb, preventing pH increase.
    • HCO3- moves into the plasma through a counter-transport mechanism, exchanging with chloride ions (Cl-) in the chloride shift (Hamburger phenomenon).
    • This helps maintain a neutral charge within the RBC membrane.

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    Description

    This quiz explores the mechanisms of gas transport and exchange in the blood, focusing on the roles of red blood cells (RBCs) in oxygen and carbon dioxide transport. It examines how gases diffuse between lungs, RBCs, and tissues, driven by pressure gradients. Test your understanding of these critical physiological processes.

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