haemoglobin Flashcards
haemoglobin structure
- quaternary protein
- four subunits, each with a haem group
- has an affinity for oxygen
what feature must haemoglobin have to efficiently transport oxygen?
must readily associate with oxygen at gas exchange surface
- must dissociate oxygen at respiring tissue
percentage saturation
oxygenated haemoglobin divided by max. saturation
x100
define partial pressure of oxygen
amount of oxygen in a mixture of gases/solution
pO2/kPa
- more O2 = more loaded = more saturated
- lower pO2 = less Hb saturated
Hb sigmoid curve
- s shaped
- first O2 molecule alters 3 structure of Hb molecule
- exposes 2nd and 3rd binding sites, easier for O2 to bind and load (co-operative nature of bonding)
- lungs have higher affinity for O2 at high pO2, Hb almost fully saturated
- Hb has lower affinity for O2 at respiring tissues at a lower pO2, oxyhaemoglobin breaks down and unloads O2
The first molecule of oxygen to bind causes a change in the shape pf the haemoglobin molecule. This change of shape makes it easier for the other oxygen molecules to bind to the Hb molecule. Explain how the graph provides evidence for this.
- at low pO2 there is a little increase in saturation
- as O2 levels increase, rapid rise in saturation
- easier for the O2 to bind
bohr shift
- at higher pCO2 Hb affinity for O2 is lower
- if pCO2 increases, Hb saturation decreases
- dissociation curve shifts RIGHT (bohR shift)
- makes blood more acidic, lowers pH
- change in ph alters 3 structure, lower affinity
heat from respiration helps mammals to maintain a constant body temperature. use this information to explain the relationship between the SA:V ratio of mammals and the dissociation curves of their Hbs.
- smaller mammals have a larger SA:V
- smaller animals have more heat loss per unit body mass
- so greater rate of respiration
- oxygen required for aerobic respiration
- Hb releases more oxygen more readily
when environmental pO2 lower (high altitude, bottom of lakes, etc)
- Hb is shifted to the left
- Hb has higher affinity for O2
- fully saturated at a lower pO2, rapidly unloads at tissues
eg: human foetus
curve shifts to the right
- higher metabolic rate (eg: cheetahs, small mice)
- Hb has lower affinity for O2
- dissociates from Hb more readily
- O2 nire readily available
the oxygen dissociation curve of the foetus is to the left of that for its mother. explain the advantage of this for the foetus
- higher affinity oxygen
- at hgih pO2
- oxygen moves from mother to foetus
explain how oxygen in a red blood cell is made available for respiration in active tissues
- CO2 produced from increased respiration
- increased O2 dissociation from Hb
- at low pO2 in tissues
- O2 diffuses from the RBCs to the tissues
Explain how oxygen is loaded, transported and unloaded in the blood.
- haemoglobin carries oxygen
- in red blood cells
- loading in lungs at high pO2
- unloads at respiring tissues at low pO2
- unloading occurs more when high pCO2
binding of one molecule of oxygen to Hb makes it easier for a second Oxygen molecule to bind. Explain why,
- binding of first O2 molecule changes the 3 structure
- uncovers another binding site
