Haemoglobin Flashcards
What reaction joins the monomers together?
Condensation reaction- peptide bonds
What is the quaternary structure?
One or more polypeptide chains
What is the prosthetic group?
Not made of amino acids- associated with the polypeptide chain- the binding site
Adaptions of red blood cells?
Biconcave shape- larger SA for short diffusion distance
No nucleus- more space for HB
Contains haemoglobin- binds and carries O2
Small (7 micrometers)- larger SA:V ratio
What does each chain of haemoglobin have?
A haem group- contains an iron ion and gives haemoglobin its red colour
Does HB have a high or low affinity for O2?
High
How many oxygen molecules can each HB molecule carry?
4
What does affinity for oxygen mean?
The tendency to combine with oxygen
Why do we need haemoglobin?
At body temperature, we have low solubility
So therefore we need a way to increase O2 transport
What is the partial pressure of a gas?
The pressure a particular gas contributes to the total pressure of the gas mixture
What is the partial pressure of oxygen?
A measure of oxygen concentration
The higher the concentration of dissolved O2 in cells?
The higher the partial pressure
What does the affinity for oxygen vary on?
The partial pressure
When does oxygen load onto haemoglobin and what does it form?
Forms oxyhaemoglobin when there is a high partial pressure
When does oxyhaemoglobin unload oxygen?
When there is a lower partial pressure
Where is partial pressure the highest out of: alveoli, resting tissue and in muscles?
In alveoli because oxygen enters blood capillaries at the alveoli to form oxyhaemoglobin
Why is partial pressure lowest in muscles?
Because when cells respire, they use up oxygen which lowers the partial pressure. Red blood cells deliver oxyhaemoglobin to respiring tissues, where it unloads its oxygen
The haemoglobin then returns to the lungs to pick up more oxygen
What is the T state?
Tense
Haem groups are tucked away in the proteins
What is the R state?
Conformational change- haem groups are more exposed to
Easier for 2nd, 3rd, 4th O2’s to bind
What do dissociation curves show us?
How saturated the haemoglobin is with O2 at any given partial pressure
What does 100% saturation mean?
Every haemoglobin is carrying the maximum of 4 molecules of O2
What does 0% saturation mean?
None of the haemoglobin molecules are carrying any oxygen
Explain why partial pressure is high and so is saturation?
Where partial pressure is high (e.g. in the lungs), haemoglobin has a high affinity for oxygen- will readily combine- therefore there is a high saturation of O2
Explain why partial pressure is low and why saturation is also low?
Where pO2 is low (e.g. respiring tissues), haemoglobin has a low affinity for oxygen- will release oxygen instead of combining with it- therefore there is a low saturation
Why is the graph S shaped?
When haemoglobin combines with the first oxygen molecule, its shape alters in a way that makes it easier for other molecules to join too
But as haemoglobin starts to become saturated, its harder for more oxygen molecules to join
The curve has a steep bit in the middle where it is easy for oxygen molecules to join and shallow bits where its harder
When the curve is steep a small change in pO2 causes a big change in the amount of oxygen carried by haemoglobin.
How is carbon dioxide transported in the blood?
5% in solution in the blood
25% binds to haemoglobin- forms carbohaemoglobin (undergoes a slight shape change)
70%- forms carbonic acid
Do haemoglobonic acid and carboamino haemoglobin have a lower or higher affinity for oxygen?
Lower affinity for oxygen
Harder for oxygen to bind
Easier for oxygen to unbind
What is the Bohr effect?
A fall in pH reduces the affinity of Hb for O2
Causes increased unloading of O2 from Hb at any partial pressure of oxygen
As rate of reaction increases and partial pressure of carbon dioxide increases, you get rapid unloading of oxygen due to the Bohr effect- there is plenty of oxygen for aerobic respiration which means that less lactic acid is produced
Does fetal Hb have a higher or lower affinity for oxygen?
Higher affinity
Allows oxygen to unload from maternal haemoglobin and load the fetal haemoglobin
Does myoglobin have a high or low affinity for oxygen?
High affinity
Oxygen stays bound unless partial pressure of oxygen is very low- then it unloads rapidly which delays anaerobic respiration
Is there lower or higher partial pressure of oxygen in high altitudes?
Lower partial pressure- is harder for collisions
Does llama haemoglobin have a higher or lower affinity for oxygen?
Higher affinity
Easier for oxygen to bind at low partial pressures of oxygen (increased loading)
Unloading occurs at lower partial pressures of oxygen
What conditions do lugworms live in?
Anoxic (very low oxygen) conditions
Live in muddy estuaries
Oxygen is less soluble in water
In anoxic conditions what is loading and unloading like?
High affinity for oxygen- loading occurs at very low oxygen
Unloading occurs at low partial pressures in tissues
Elephant?
Hb has a higher affinity for oxygen- lower SA:V ratio
Slower rate of heat loss
Slower metabolic rate
Having a higher affinity of Hb for oxygen is beneficial- ensures oxygen is not unloaded too quickly
Mouse?
Hb has a lower affinity for oxygen- higher SA:V ratio Slower
Faster rate of heat loss
More active
Faster metabolic rate
Lower affinity of Hb for oxygen enables more rapid unloading
