Haemoglobin Flashcards
What is the most specialised role of the blood?
The transport of oxygen from the lungs to cells of the body by erythrocytes.
How are erythrocytes specialised?
Biconcave shape- max SA and helps squeeze through narrow capillaries.
No nucleus- max amount of Hb and limits life to 120 days.
What is Haemoglobin?
The red pigment in red blood cells that carries oxygen. It also gives RBC their colour.
What type of molecule is haemoglobin?
A very large globular conjugated protein.
Made up of 4 peptide chains.
What is formed when oxygen binds to haemoglobin?
What is the equation for this?
Oxyhaemoglobin.
Hb + 4O2 ==> Hb(O2)4
Are the oxygen levels in the cells low or high when they reach the capillaries in the lungs?
Low
How is a steep concentration gradient created between the inside of erythrocytes and air of alveoli?
It is created by the low oxygen level in the RBC compared to the high oxygen levels in the air of the alveoli in the lungs.
What is positive cooperativity?
When one oxygen molecule binds to a haem group, the molecule changes shape, making it easier for the next oxygens to bind.
How is the steep concentration gradient maintained (between the alveoli and the cells)?
A steep conc. gradient stays until all the haemoglobin is saturated with oxygen.
Is the concentration of oxygen lower in the body cells or in the erythrocytes when the blood reaches the body tissues from the lungs?
Lower in the body cells
What is partial pressure?
The concentration of a chemical when it is one of a mixture of gases.
What is on the axis of an oxygen dissociation curve?
Percentage saturation of haemoglobin in the blood is plotted against the partial pressure of oxygen.
What do oxygen dissociation curves represent?
They show the affinity of haemoglobin for oxygen.
Why does a small change in partial pressure of oxygen in the surroundings make a significant difference to the saturation of haemoglobin with oxygen?
Because when the first molecule of oxygen attaches to haemoglobin, it changes shape so oxygen can be rapidly added to haemoglobin.
Why does the curve level out at the highest partial pressure of oxygen?
All the haem groups are bound to oxygen so the haemoglobin is saturated and cannot take up any more.
What happens at high partial pressures of oxygen in the lungs?
Haemoglobin in RBC is rapidly loaded with oxygen.
Hb picks up oxygen more easily.
What happens at low partial pressures of oxygen in the respiring tissues?
Oxygen is released rapidly from the haemoglobin to diffuse into the cells.
Hb does not carry as much oxygen.
What happens to the oxygen in the blood when you aren’t very active?
Only about 25% of the oxygen is released into the body cells.
What is the Bohr Effect?
At higher partial pressures of carbon dioxide, haemoglobin gives up oxygen more easily.
Why is the Bohr effect important in the body?
Because as a result;
1) in active tissues with high pCO2, Hb gives up its oxygen more readily.
2) in the lungs where pCO2 is low, oxygen binds to Hb molecules easily.
How does a fetus get the oxygen it needs?
Oxygenated blood from the mother runs close to the deoxygenated fetal blood in the placenta.
Does fetal haemoglobin have a higher or lower affinity for oxygen than adult haemoglobin?
Higher
If fetal haemoglobin had the same affinity for oxygen as the mother, what would be the case?
Little to no oxygen would be transferred to the blood of the fetus.
Fill in the blanks.
As the proportion of CO2 …………… , the oxygen dissociation curve for Hb moves to the …………….. .
increases
right
Is the curve for fetal Hb to the left or right of the adult Hb curve?
to the left of
Carbon dioxide is transported from the tissues to the lungs in three ways. What are they?
1) Dissolved in the plasma
2) Combined with amino groups in Hb to form carbominohaemoglobin
3) Converted into hydrogen carbonate ions in the RBC
Which way is the majority of carbon dioxide transported to the lungs?
In the form of hydrogen carbonate ions (HCO3-)
What is the equation of the formation of carbonic acid in the red blood cells?
CO2 + H2O ===> H2CO3
What does carbonic acid dissociate into and what is the equation for this?
Dissociates into hydrogen carbonate ions and hydrogen ions.
H2CO3 ===> H+ + HCO3-
What enzyme is there high levels of in the red blood cells that catalyses the reaction between CO2 and water to give carbonic acid?
Carbonic anhydrase
What happens to the negative hydrogen carbonate ions in the erythrocyte?
They diffuse out of the erythrocyte down a concentration gradient.
What moves into the RBC once HCO3- ions diffuse out, to maintain the electrical balance of the cell?
Chloride ions
What is the process called when HCO3- leaves the cell and Cl- enters the cell?
Chloride shift.
How is a steep conc gradient kept to allow more carbon dioxide to enter the erythrocyte?
By converting carbon dioxide into HCO3- ions.
When does carbonic anhydrase turn carbonic acid back into water and carbon dioxide?
When the blood has reached the lungs where there is a low conc of CO2.
What happens to the H+ ions in the red blood cell?
Haemoglobin acts as a buffer and accepts H+ ions to form haemoglobinic acid.
How does carbon dioxide leave the cell to enter the lungs to then be exhaled out of the body?
HCO3- ions go back in the RBC
They react with H+ ions to form more carbonic acid
This is broken down by carbonic anhydrase
Free carbon dioxide is released
This CO2 diffuses into the lungs.
