8.4 Transport Of O2 & CO2 in Blood Flashcards
What shape do erythrocytes have (Red blood cells)?
biconcave so there’s a larger SA for diffusion
Where are erythrocytes made
in red bone marrow (adults)
Why don’t erythrocytes have a nucleus
so there’s more space for haemoglobin and it limits their lifespan; they only last about 120 days in the bloodstream
What is haemoglobin made up of
globular conjugated protein, 4 peptide chains, each with an iron-containing haem prosthetic group.
How many bonds can haemoglobin make
can bond to 4 oxygen molecules
What is the product of joining haemoglobin to oxygen
oxyhaemoglobin (reversible reaction)
What is the product of joining haemoglobin to oxygen
oxyhaemoglobin (reversible reaction)
What is positive cooperativity in joining oxygen to haemoglobin
When one oxygen binds, the haemoglobin changes shape so the other 3 oxygens can bind easier
What happens when the oxygen-saturated haemoglobin travels to the cells
Because the oxygen levels in the cells is now lower than the oxygen in the erythrocytes, the oxygen easily moves down the concentration gradient to go into the cells.
What do oxygen dissociation curves show
the affinity of haemoglobin for oxygen; on the axis are ‘% saturation of haemoglobin in the blood’ (Y-AXIS) and ‘partial pressure of oxygen’ (X-AXIS).
What do results show in an oxygen dissociation curve
It increases steadily and rapidly because as soon as one oxygen binds, the other 3 rapidly bind after it, because the shape of haemoglobin changes to accommodate this addition; towards the end it levels off because the haemoglobin would be fully saturated and cannot bind to anymore oxygen
Why is only 25% of oxygen released into cells when at rest
Because the demand is low so the body stores the rest as a reservoir for when demand suddenly increases
What is the Bohr effect
When the partial pressure of CO2 rises, haemoglobin gives up oxygen more easily - known as the Bohr effect
What happens as a result of the Bohr effect that makes it so important
- haemoglobin gives up oxygen more readily in active tissues with a high partial pressure of CO2
- in the lungs where the proportion of CO2 in the air is relatively low, oxygen binds to haemoglobin molecules more readily.
Why must the foetus’ affinity for oxygen be much higher than the mother’s when in the womb
because it readily transfers oxygen into the baby’s deoxygenated blood from the mother’s oxygenated blood supply.
What are the 3 ways CO2 is transported in the blood
- 5% is dissolved in the plasma
- 10-20% is combined with amino acids in polypeptide chains of haemoglobin to form carbaminohaemoglobin
- 75-85% is converted into hydrogen carbonate ions in cytoplasm of RBCs
What is formed when CO2 slowly reacts with water
carbonic acid —> this dissociates to form hydrogen ions and hydrogen carbonate ions.
What enzyme is used to reverse the reaction back to carbonic acid
carbonic anhydrase (found in cytoplasm of RBCs) Using CO2 and water ---> carbonic acid the dissociates to form carbonic ions and hydrogen ions.
What is the chloride shift
When negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma by diffusion, down the conc. gradient. Chloride ions move back in to the erythrocytes, which maintains the electrical balance of the cell.
What is haemoglobinic acid and how is it formed
haemoglobin in the erythrocytes reacts acts as a buffer and prevents changes in the in the pH by accepting free hydrogen ions in a reversible reaction to form HAEMOGLOBINIC ACID
