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What percentage of oxygen is dissolved in blood plasma?
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.
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Match the gas with its corresponding pressure in the tissues:
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What drives the passive diffusion of gases during gas exchange?
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Hemoglobin only temporarily binds to oxygen and carbon dioxide.
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At what pressure (in mmHg) does oxygen move from the alveoli into the pulmonary capillaries?
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What percentage of oxygen is released from hemoglobin at the tissues during normal activity?
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Higher temperature decreases hemoglobin's ability to bind oxygen.
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What is the primary way carbon dioxide is transported in the bloodstream?
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What happens to oxygen when the partial pressure of O2 (PO2) increases?
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The process of CO2 combining with water to form carbonic acid is catalyzed by __________.
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Hemoglobin is 100% saturated with oxygen at a PO2 of 100 mm Hg.
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Match each factor with its effect on hemoglobin's ability to bind oxygen:
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Which of the following contributes to the release of oxygen from hemoglobin?
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What occurs in the tissue capillaries regarding oxygen transport?
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Only 7% of carbon dioxide travels in the bloodstream dissolved directly in plasma.
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At a low PO2, hemoglobin has a saturation level of _____%.
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What is formed when carbon dioxide reacts with hemoglobin?
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How does cooperative binding affect hemoglobin's affinity for O2?
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Match the following PO2 values with their corresponding hemoglobin saturation levels:
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At high PO2 levels, hemoglobin releases more O2 to tissues.
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What shape does the oxygen-hemoglobin dissociation curve take?
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What is the primary function of the chloride shift in red blood cells?
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93% of carbon dioxide is transported in the bloodstream dissolved in plasma.
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What is carbaminohemoglobin?
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The process of converting CO2 to H2CO3 is facilitated by __________.
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Match the following components related to gas transport with their respective functions:
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Which percentage of carbon dioxide is transported as bicarbonate (HCO3−)?
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The dissociation curve of oxygen-Hb indicates that hemoglobin saturates with oxygen under high pressure of oxygen.
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Name two ways in which oxygen is transported in the bloodstream.
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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.
