Haemoglobin Flashcards
describe the transport of oxygen in large organisms
- a smaller surface area to volume ratio
-so simple diffusion is not sufficient - therefore organisms circulate blood around their bodies to carry oxygen to respiring tissues
describe the structure of haemoglobin
- complex protein with a quaternary structure
- composed of 4 polypeptide subunits
-each containing a HAEM group - each haem (Fe2+ ) group can bind with one O2 molecule
- So four O2 molecules in total
how many molecules of haemoglobin does an Erythrocyte (rbc) contain approx ?
approx. 300 million molecules
when oxygen binds with haemoglobin, what is formed?
OXYHAEMOGLOBIN
in a reversible reaction but does not always bind to 4 molecules of O2
What is saturation? and how do we calculate percentage saturation
the amount of oxygen combined is described in terms of percentage saturation which is ;
= oxygenated haemoglobin / maximum saturation x 100
describe cooperative O2 loading :
- the 1st o2 molecule alters the tertiary structure of the Hb molecule
- this exposes the 2nd and 3rd o2 binding sites
- which is easier to bind and load
what is the definition of partial pressure of oxygen (pO2 / kPa )
the proportion of oxygen in a mixture of gases or a solution
eg. higher pO2 > more oxygen loaded > haemoglobin is more saturated
define loading/association , unloading/ dissociation , affinity.
loading: when oxygen is taken up my hb
unloading: when oxygen is released by hb
affinity: a natural attraction to something
what shape is an oxygen dissociation curve?
S shaped - sigmoid curve
representing the cooperative nature of oxygen binding
describe the pO2 in lungs
- pO2 is high in capillaries (about 13.16kPa)
- Hb has a higher affinity for O2 at a high pO2
- Hb becomes fully saturated as the RBC pass through the pulmonary capillaries in lungs
- 98% + staurated
describe the pO2 in respiring tissues
- pO2 in the tissue capillaries is LOWER ( only 5.0 kPa)
- Hb now has a lower affinity to O2 at a lower pO2
- so oxyhaemoglobin starts to breakdown and unloads oxygen
- to be used for aerobic respiration
explain the effect of increased respiration rate on the oxygen dissociation
1- tissue cells respire aerobically quickly reducing the dissolved O2
2- this reduces the pO2 to a LOWER level
3- the oxygenated blood arriving with fully saturated Hb begins to unload more oxygen and becomes less saturated
4- so more oxygen will be released from the haemoglobin to the tissue cells
5- because the surrounding pO2 is lower and so haemoglobin will have an even lower affinity to oxygen
if a question asks what happens to % saturation at either low or high p02 , what would u do?
- draw a line from either high or low pO2
upto the sigmoid curve and across to the Y axis to see the effect on Hb% saturation
% of oxygen unloaded = lungs(high) - tissues(low)
describe the effect of CO2 concentration on the affinity of oxygen- bohR Shift
-if pCO2 increases the saturation of haemoglobin decreases
- this causes the haemoglobin-oxygen dissociation curve to the RIGHT
what happens when the haemoglobin-oxygen dissociation curve shifts to the right?
- Hb will have low affinity to oxygen at the respiring cells
- so more O2 is unloaded, at the SAME pO2
-more oxygen is available to meet the oxygen demands
Heat from respiration helps mammals to maintain a constant body temperature.
use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobin -5
- smaller mammal has greater SA : VR
- so there is more heat lost
- and so has a greater rate of respiration / metabolism
-oxygen is required for aerobic respiration - haemoglobin releases more oxygen
where are the three basic types of haemoglobin found?
1- in adult humans and other species that live on land at sea level
2- in species that live in environments where the environmental pO2 is lower ( high altitude, bottom of lakes )
3- right shifted curve of species that have a Higher metabolic rate (cheetah , small mice)
describe the properties of haemoglobin in species that live in environments where the environmental pO2 is lower ( high altitude, bottom of lakes ).
- the dissociation curve is shifted to the left
- hb has higher affinity for O2
- becomes fully saturated at a lower pO2 and rapidly unloads oxygen
- has a similar curve to human foetal haemoglobin
describe the properties of haemoglobin in species that have right shifted curve and have a Higher metabolic rate (cheetah , small mice)
- hb has a lower affinity for O2
- so dissociates from the haemoglobin more readily
- O2 is more readily available to respiring cells
the oxygen dissociation curve of the foetus is to the left of that for its mother.
Explain the advantage of this for the foetus
1- higher affinity to O2
2- at low/same/high partial pressure
3- oxygen moves from mother to foetus
why would the lugworm require haemoglobin more like the curve towards the left ?
- Hb has high affinity for oxygen which enables the lugworm to saturate haemoglobin at low pO2 as between tides the O2 concentration in the burrow will be very low
-tissues will have a slightly lower pO2 and steep curve means oxygen will still unload at the tissue when required.
Explain how oxygen is loaded, transported and unloaded in the blood (6)
1- haemoglobin carries oxygen ( has a high affinity)
2- in red blood cells
3- loading/association in lungs
4- at high pO2
5- unloading/dissociation to tissues
6- at low pO2
7- unloading linked to higher carbon dioxide concentration
