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Respiratory System. Gas Transport. Gas Transport. Oxygen and carbon dioxide are carried between the lungs and body cells by the blood These gases can be: Dissolved into blood plasma Or, chemically combined with other atoms or molecules present in the blood. Oxygen Transport.
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Respiratory System Gas Transport
Gas Transport • Oxygen and carbon dioxide are carried between the lungs and body cells by the blood • These gases can be: • Dissolved into blood plasma • Or, chemically combined with other atoms or molecules present in the blood
Oxygen Transport • Oxygen can be carried in the blood by: • Loosely binding to the iron present in the protein hemoglobin in the red blood cells (creating a new compound called oxyhemoglobin). • Or, dissolving in the plasma.
Oxygen Transport • Transport via hemoglobin: • Accounts for over 98% of oxygen transport • The amount of oxygen that hemoglobin binds is determined by the partial pressure of the oxygen
Oxygen Transport • Transport via hemoglobin: • Greater partial pressure leads to an increase in the number of oxygen molecules bound to hemoglobin • Oxygen atoms continue to be bound to hemoglobin until the hemoglobin is saturated • Each molecule of hemoglobin can bind up to four oxygen molecules
Oxygen Transport • Transport via hemoglobin: • Oxygen is released from the oxyhemoglobin molecule as the partial pressure of oxygen decreases • The number of oxygen molecules released increases when: • Oxygen is used for respiration in nearby tissues • Partial pressure of carbon dioxide in the blood increases • Acidity increases • Temperature increases
Carbon Dioxide Transport • Carbon dioxide is transported: • Dissolved in plasma (about 7%) • Bound to hemoglobin (15% to 25%) • As part of a bicarbonate ion (about 70%)
Carbon Dioxide Transport • Transport via plasma: • Amount of carbon dioxide dissolved in plasma is determined by the partial pressure of carbon dioxide • The higher the partial pressure of carbon dioxide in nearby tissues the higher the amount dissolved into solution
Carbon Dioxide Transport • Transport via hemoglobin: • Carbon dioxide loosely binds to the amino groups (-NH2) of hemoglobin to form the compound carbaminohemoglobin(very slow process) • Carbon dioxide is released from carbaminohemoglobin when the partial pressure of carbon dioxide is low
Carbon Dioxide Transport • Transport via bicarbonate ions: • Carbon dioxide enters the red blood cells and combines with water to form carbonic acid • This process is normally very slow but is very quick in the red blood cells where the enzyme carbonic anhydrase is present
Carbon Dioxide Transport • Transport via bicarbonate ions: • After carbonic acid forms in the red blood cells it immediately dissociates releasing hydrogen ions and bicarbonate ions • The hydrogen ions bind to deoxyhemoglobin in the red blood cells • The bicarbonate ions diffuse back into the blood plasma and are replaced in the red blood cells by chloride ions from the plasma (called the chloride shift)
Carbon Dioxide Transport • Transport via bicarbonate ions: • As blood passes into the capillaries of the lungs, dissolved CO2 diffuses into the alveoli, dropping the partial pressure of carbon dioxide in the plasma • As this happens, hydrogen ions and bicarbonate ions in the red blood cells recombine to form carbonic acid, which then quickly forms carbon dioxide and water