Haemoglobin Curves Flashcards
Features of an erythrocytes
(Rbc)
Biconcave- large SA:V for diffusion of O2
Flat and thin-short diffusion path for oxygen to reach all haemoglobin in cell
What is haemoglobin
Globular structure (quaternary structure) made up of 4 polypeptide chains
Each chain has a haem group which contains an iron ion which gives it the red colour
Each haemoglobin molecule can bind to up to 4 oxygen molecules
What is association
When oxygen binds to the haemoglobin to form oxyhaemoglobin
( can be called loading of oxygen )
What is dissociation
When oxygen is removed from the oxyhaemoglobin to form haemoglobin again
( can be called unloading of oxygen )
What is the equation for association and dissociation
Hb + 4O2 (reversible arrow ) HbO8
What is haemoglobin’s relationship with oxygen
Has a high affinity to oxygen - takes up oxygen EASILY and releases is LESS easily
Has a low affinity to oxygen - DOESNT take up oygen easily but releases it READILY
What is haemoglobin’s affinity for oxygen dependent on
- the partial pressure of oxygen (pO2)
- haemoglobin saturation (eg no more areas on haemoglobin for oxygen to bind to)
- the partial pressure of carbon dioxide (pCO2)
What is partial pressure
Measure of concentration of that gas in a mixture of gases
In the gas exchange tissue what is the O2 conc, the CO2 conc, the affinity of haemoglobin for oxygen and the result
O2 conc=high
CO2 con=low
Affinity=high
= oxygen associated
In respiring tissue what is the O2 conc, the CO2 conc, the affinity of haemoglobin for oxygen and the result
O2 conc=low
CO2 conc= high
Affinity=low
=oxygen is dissociated
Explain why dissociation curves are S shape
As each O2 molecule binds it changes the shape of the haemoglobin in a way that makes it easier for further oxygen molecules to bind (Co-operative binding).
As saturation of haemoglobin increases it becomes harder for the final oxygen molecules to bind. This means the saturation of haemoglobin with increasing pO2 is not linear
Early on, as the pO₂ increases, hemoglobin’s saturation rises quickly because it’s relatively easy for oxygen molecules to bind. But as the pO₂ continues to increase, the curve starts to flatten because the hemoglobin is approaching its maximum saturation, and it becomes harder for additional oxygen molecules to bind.
Why is there a slow start to the graph
At low partial pressure of oxygen the haemoglobin has a low affinity for oxygen so it has a low saturation of oxygen
Why is there a steep section
Cooperative bonding
Easy for oxygen to bind as partial pressure of oxygen increases so a small increase in pO2 = a large increase in amount of oxygen being carried by haemoglobin
Why is there a shallow gradient
Harder for oxygen to bind as haemoglobin is nearly saturated
What does it mean if the curve shifts left
The haemoglobin has a higher affinity for oxygen
There is less co2 so less respiration occurring
What does it mean when the curve shifts right
There is an increase in co2
It shows that for the same partial pressure the saturation of blood with oxygen is lower as more oxygen is being released from haemoglobin
Most respiration is occurring so more oxygen will be released
For a foetus the curve shifts…. Amd why
To the left
Higher affinity
And low oxygen in the environment
Foetal haemoglobin has a greater affinity to oxygen so oxygen binds more easily and is more reluctant to dissociate this is so the foetal haemoglobin needs to steal oxygen from the mothers
For an animal living in low oxygen environments the curve shifts to the …. And why
Left
Higher affinity
Low oxygen
Environment either high altitude so low pO2 or in sand or seabed so less oxygen available
Haemoglobin has higher affinity so it is able to load more oxygen at lower pO2
How does the curve shift for small organisms with high SA or high metabolic rate and why
Right
Lower affinity
High respiration
Small SA:V lose heat more quickly so higher metabolic rate to maintain body temp so high respiration needed
High metabolic rate= more respiration = greater oxygen demand so organism need haemoglobin with lower affinity as they need to easily unload oxygen to meet high oxygen demand amd allow faster respiration rate
Which way does myoglobin make the curve shift
To the left
