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19 Cards in this Set
- Front
- Back
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How does oxygen move into the RBCs? |
When they enter the capillaries in the lungs, they have low amounts of O2, so there is a steep conc. gradient between the air in the alveoli and the inside of RBCs so O2 binds with haemoglobin |
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What is positive cooperativity? |
When an O2 molecule binds to a haem group the molecule changes shape making it easier for the next O2 molecules to bind until the molecule is saturated with O2 |
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How does oxygen move out of the RBCs? |
When it reaches the body tissue the conc. of O2 in the cytoplasm of cells is lower than inside of RBCs so O2 moves out of the RBCs down a conc. gradient |
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How is positive cooperativity exhibited when oxygen is unloaded to cells? |
Once the O2 molecule is released the molecule changes shape and it becomes easier to remove the remaining O2 molecules |
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What is an oxygen dissociation Curve? |
Where the percentage saturation in haemoglobin is plotted against the partial pressure of O2 |
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What is partial pressure? |
It describes the conc. of O2 when it is one of a mixture of gases (pO2) |
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What does the oxygen dissociation curve show us? |
Affinity of haemoglobin for oxygen relative to its partial pressure |
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Why is the oxygen dissociation Curve steep in the middle? |
At higher PO2 more haem groups are bound to O2 making it easier for more O2 to be picked up (positive cooperativity) |
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What is the Bohr effect? |
As the partial pressure of CO2 Rises haemoglobin gives up O2 more easily to accomodate the CO2 and provide tissue with more O2 |
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What is the difference in fetal haemoglobin and why is this difference important? |
Fetal haemoglobin has a higher affinity for O2 at every point on the dissociation curve It takes up O2 in a lower pO2 (in the placenta) where oxygen in adult oxyhaemoglobin dissociates |
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What are the three ways CO2 is transported to the lungs from the tissue? |
A small amount is dissolved in the plasma A larger amount is held in the haemoglobin Most of it is converted into HCO3- in the cytoplasm of RBCs |
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How is CO2 transported in haemoglobin? |
It combines with amino groups in polypeptides and haemoglobin to form a compound called carbaminohemoglobin |
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What is the equation for CO2 reacting in the cytoplasm of the RBC and what is needed for the reaction? |
CO2 + H2O -><- H2CO3 (carbonic acid) -><- H+ + HCO3- Carbonic anhydrase enzyme which catalyses the reaction to form carbonic acid |
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What happens once the HCO3 - forms? |
It Moves out of the RBC into the plasma by diffusion down a conc. gradient. Cl- ions move into the RBC which maintains the electrical balance of the cell (chloride shift) |
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Why is it important that HCO3- is removed from the RBC? |
So that the RBC can maintain a steep conc. gradient for CO2 to diffuse out of respiring tissue |
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How is CO2 unloaded from the RBC into the alveoli? |
When the blood reaches the lungs where there is a low conc. of CO2, carbonic anhydrase catalyses the reverse reaction breaking down H2CO3 into CO2 and H2O, which diffuses out of the RBC once the HCO3- moves back into the RBC |
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How does Cl- ions move out of the RBC? |
They diffuse back into the plasma down and electrochemical gradient |
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When H+ and HCO3 - is created in the reversible reaction, where do the H+ ions go? |
Haemoglobin acts as a buffer and prevents pH change by accepting H+ ions to form haemoglobinic acid |
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What does the effect of the Bohr shift look like on the dissociation curve look like and why? |
A curve to the right of the normal curve It is harder for oxygen to bind so a higher pO2 is needed for it to bind |
