module 3.2 Flashcards
what protein do erythrocytes contain
haemoglobin
haemoglobin + oxygen–>
haemoglobin + oxygen–>oxyhaemoglobin
what dos each haem group of haemoglobin contain
a single iron ion (Fe2+)
what can iron ions do in haemoglobin
attract and hold an oxygen molecule
what does affinity mean
attraction
what does dissociation mean in terms of haemoglobin
releasing the oxygen from oxyhaemoglobin
what is foetal haemoglobin
the type of haemoglobin usually only found in the foetus
what does haemoglobin have a HIGH affinity for
oxygen
state the process of the transport of oxygen
oxygen is absorbed in the blood as it passes the alveoli in the lungs . o2 molecules diffusing into the blood plasma enter the red blood cells. here they become associated with the haemoglobin (it binds reversibly ). this takes oxygen out of solution so maintains a steep conc gradient, allowing more o2 to enter the blood from the lungs and diffuse into cells.
the blood carries oxygen from the lungs back to the heart, before travelling around the body to supply the tissues. in body tissues, cells need o2 for aerobic respiration. thus haemoglobin must eb able to release oxygen (dissociate)!
what does the ability of haemoglobin to associate and release oxygen depend on
the conc of o2 in the surrounding tissues
what is the conc of o2 measured by
by the relative pressure that it contributes to a mixture of gasses. this is called the partial pressure of o2 or pO2, its also called the oxygen tension and measured in kPa
what sort of curve does the association of oxygen with haemoglobin create and what is this curve called
S-shaped curve- this is called the haemoglobin dissociation curve.
describe the haemoglobin dissociation curve and why its shaped like this (bottom of the curve)
at low oxygen tension, the haemoglobin does not readily associate with o2 molecules. This is because haem groups that attract oxygen are in the centre of the haemoglobin molecule. This makes it difficult for the o2 molecule to reach the haem group and associate with it. this difficulty in combining with 1st o2 molecule accounts for the low saturation level of haemoglobin at low o2 tensions.
describe the haemoglobin dissociation curve and why its shaped like this (middle of the curve)
as o2 tension rises, diffusion grad into haemoglobin increases. eventually, 1 o2 molecule enters haemoglobin and associates with one of the haem groups causing a conformational change allowing o2 molecules to enter haemoglobin and associate with other haem groups relatively easy.- this accounts for the steepness as the o2 tension rises
describe the haemoglobin dissociation curve and why its shaped like this (top of the curve)
as haemoglobin reaches 100% saturation, the curve levels off.
talk about the oxygen tension in the lungs and the oxygen tension in the respiring body tissues
o2 tension in the lungs is sufficient to produce close to 100% saturation. The o2 tension in respiring body cells is sufficiently low to cause oxygen to dissociate readily from the oxyhaemoglobin.
how is fetal hemoglobin different to adult hemoglobin- talk about curve too
it has a higher affinity for oxygen thus the hemoglobin dissociation curve is to the left of the adult curve.
why does fetal hemoglobin have a higher affinity than adult hemoglobin
because fetal hemoglobin must be able to associate with o2 in an environment where o2 tension is low enough to make adult hemoglobin release o2
in the placenta, is o2 tension low or high
low
what does the fetal hemoglobin do and what dos this do to the o2 tension. what does it do to the mothers blood
in the placenta where o2 tension is low, fetal hemoglobin will absorb o2 from the surrounding fluid, this reduces o2 tension even further, as a result oxygen diffuses from the mothers blood into the placenta- this reduces o2 tension within the mothers blood which makes the maternal hemoglobin release more o2 (dissociation)
what are the 3 ways co2 is transported
- dissolved directly in placenta (5%)
-combined with hemoglobin to form a compound called carbaminhaemoglobin (10%)
-transported in the form of hydrogen carbonate ions (HCO3-)
Describe the formation of hydrogen carbonate ions (4 STEPS) (6)
-co2 in the blood plasma diffuses into red blood cells, here it combines with a weak acid called carbonic acid. this reaction is catalyzed by carbonic anhydrase.
CO2+H20–>H2CO3
-This carbonic acid dissociates to release H+ ions and hydrogen carbonate ions(HCO3-)
-The hydrogen carbonate ions diffuse out of the red blood cells into the plasma. the charge inside the red blood cell is maintained by the movement of cl- ions from the plasma into the red blood cell-this is the chloride shift.
-the hydrogen ions building up in the red blood cell could cause contents of red blood cell to become v acidic. to prevent this, H+ ions are taken out of solution by associating with hemoglobin to produce hemoglobinic acid. the hemoglobin is acting as a buffer
