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wrote...
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11 years ago
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Oxygen in picked up in the lungs by hemoglobin which is found in red blood cells. The hemoglobin then transports the oxygen (4 oxygens can be carried at one time by one cell) to cells that need it and when they release the oxygen, they pick up carbon dioxide. They then carry the carbon dioxide back to the lungs where most of it is exhaled. the whole process is mediated by chemical triggers in the body.
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wrote...
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11 years ago
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Oxygen is breathed in through the lungs and diffuses into the circulatory system where it is transported 98.5% via the haemoglobin molecule (reb blood cells), and 1.5% in the plasma (solution), which contributes to the partial pressure of oxygen in the body. When oxygen reaches its destination (cells) it is released. Carbon dioxide is excreted from cells transported approx 60% via Bicarbonate, 20% via haemoglobin and 10% in plasma (contributing to the partial pressure of Co2 in the body). The bicarbonate reaction is carbon dioxide mixes with H20 in the presence of carbonic anhydrase (enzyme) to form H2Co3, which breaks up into the bicarbonate ion HCo3- and free H+. It is only TRANSPORTED in this way and when it reaches its destination the reaction occurs in reverse to reform CO2, which is then excreted from the body (through breathing).
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wrote...
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11 years ago
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Oxygen Transport
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General Cell Metabolism
Cell metabolism is based on the same general principle as the
combustion of any fuel, whether it be in the automobile, power
plant, or a home furnace. The general combustion reaction is:
CH2O (fuel) + O2 ===>
CO2 + HOH
The same reaction occurs in the cells. The "fuel" comes from
food in the form of carbohydrates, fats, and proteins.
The important principle to remember is that oxygen is
needed by the cell and that carbon dioxide is produced as a
waste product of the cell. Carbon dioxide must be expelled from
the cells and the body.
The lungs serve to exchange the two gases in the blood.
Oxygen enters the blood from the lungs and carbon dioxide is
expelled out of the blood into the lungs. The blood serves to
transport both gases. Oxygen is carried to the cells. Carbon
dioxide is carried away from the cells.
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Gaseous Diffusion:
Partial pressures are used to designate the concentrations of
gases. Dalton's Law of Partial Pressures states that the total
pressure of all gases is equal to the sum of the partial
pressures of each gas. For example, the total atmospheric
pressure of air is 760 mm Hg. In equation form:
P(total air) = P(O 2)
+ P(N2) + P(CO2) + P(HOH)
760 = 160 + 594.7 + 0.3 +5.0
The partial pressures for oxygen and carbon dioxide in
various locations are given in Figure 1. The movement or
exchange of gases between the lungs, blood, and tissue cells is
controlled by a diffusion process.
The gas diffusion principle is: A gas diffuses from an
area of higher partial pressure to an area of lower partial
pressure.
QUES. Starting with O2 in
inhaled air, describe in your own words the sequence of gas
movements from the inhalation of oxygen to the exhalation of
carbon dioxide.
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Oxygen Transport
In the lungs, oxygen diffuses from alveolar air into the
blood because the venous blood has a lower partial pressure. The
oxygen dissolves in the blood. Only a small amount is carried as
a physical solution (0.31 ml per 100 ml). The remainder of the
oxygen is carried in chemical combination with the hemoglobin in
red blood cells (erthrocytes).
Hemoglobin (molecular weight of 68,000) is made from 4 hemes,
a porphyrin ring containing iron and globin, a 4 protein chains.
Oxygen is bound to the iron for the transport process.
Hemoglobin (HHgb) behaves as a weak acid (K = 1.4 x 10-8;
pKa = 7.85). Oxyhemoglobin (HHgbO2) also behaves as a
weak acid (K = 2.5 x 10-7; pKa = 6.6)
Because both forms of hemoglobin are weak acids, and a
relationship of the numerical values of the equilibrium
constants, the net reaction for the interaction of oxygen with
hemoglobin results in the following equilibrium:
HHgb + O 2 <===>
HgbO 2 +
H+
If 2 is
increased in the blood at the lungs, the equilibrium shifts to
the right and H+ ions
increase.
Oxyhemoglobin can be caused to release oxygen by the addition
of H+ ions
at the cells. The difference in pH (7.44) of arterial blood and
venous blood (pH = 7.35) is sufficient to cause release of
oxygen from hemoglobin at the tissue cells.
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wrote...
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11 years ago
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Carbon Dioxide Transport
1. Carbon dioxide is transported in the blood in three ways: 7–10% is dissolved in plasma, 20% is carried on hemoglobin bound to globins, and 70% exists as bicarbonate, an important buffer of blood pH.
2. The Haldane Effect encourages CO2 exchange in the lungs and tissues: When plasma partial pressure of oxygen and oxygen saturation of hemoglobin decrease, more CO2 can be carried in the blood.
3. The carbonic acid–bicarbonate buffer system of the blood is formed when CO2 combines with water and dissociates, producing carbonic acid and bicarbonate ions that can release or absorb hydrogen ions.
Oxygen Transport
1. Because molecular oxygen is poorly soluble in the blood, only 1.5% is dissolved in plasma, while the remaining 98.5% must be carried on hemoglobin.
a. Up to four oxygen molecules can be reversibly bound to a molecule of hemoglobin—one oxygen on each iron.
b. The affinity of hemoglobin for oxygen changes with each successive oxygen that is bound or released, making oxygen loading and unloading very efficient.
2. At higher plasma partial pressures of oxygen, hemoglobin unloads little oxygen, but if plasma partial pressure falls dramatically, such as during vigorous exercise, much more oxygen can be unloaded to the tissues.
3. Temperature, blood pH, PCO2, and the amount of BPG in the blood all influence hemoglobin saturation at a given partial pressure.
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- Master of Science in Biology
- Bachelor of Science
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wrote...
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11 years ago
Thanks for your answers 
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