Haemoglobin Flashcards
What is the main problem that larger organisms face regarding oxygen transport?
Smaller surface area to volume ratios make simple diffusion insufficient
Larger organisms require alternative methods, such as blood circulation, to transport oxygen efficiently.
What is the role of haemoglobin in oxygen transport?
Haemoglobin is a complex protein that carries oxygen in the blood
It has a quaternary structure composed of four polypeptide subunits, each containing a haem group.
How many oxygen molecules can one haemoglobin molecule carry?
Four oxygen molecules (O2)
Each haem group within haemoglobin can bind to one molecule of oxygen.
What is the term used to describe oxygen combined with haemoglobin?
Oxyhaemoglobin
This occurs when oxygen binds to haemoglobin.
What does the percentage saturation of haemoglobin indicate?
The amount of oxygen combined with haemoglobin
It is expressed as a percentage of the maximum capacity.
What does a higher partial pressure of oxygen (pO2) result in regarding haemoglobin?
Increased loading of oxygen onto haemoglobin
Higher pO2 means more haemoglobin saturation.
What is the effect of low pO2 on haemoglobin saturation?
Lower saturation of haemoglobin
Less oxygen is loaded onto haemoglobin at lower pO2 levels.
What happens to oxyhaemoglobin in areas of low oxygen concentration?
Oxyhaemoglobin unloads oxygen to the surrounding tissues
This process is essential for supplying oxygen to respiring cells.
Define loading in the context of haemoglobin.
The uptake of oxygen by haemoglobin
This occurs in environments with high pO2.
Define unloading in the context of haemoglobin.
The release of oxygen from haemoglobin
This occurs in areas with low pO2.
What is the ‘Bohr shift’?
A rightward shift in the oxygen dissociation curve due to increased pCO2
This results in lower affinity of haemoglobin for oxygen.
How does increased carbon dioxide concentration affect oxygen unloading?
It increases the amount of oxygen unloaded from haemoglobin
Higher CO2 levels decrease haemoglobin’s affinity for oxygen.
What is the significance of the sigmoid shape of the oxygen dissociation curve?
It reflects the cooperative nature of oxygen loading
The binding of the first oxygen molecule increases the likelihood of subsequent oxygen molecules binding.
What is the effect of high altitude on haemoglobin affinity for oxygen?
Haemoglobin has a higher affinity for oxygen
This allows for saturation at lower pO2 levels.
What adaptations do smaller mammals have regarding oxygen transport?
Higher metabolic rates and lower affinity for oxygen
This helps them unload oxygen more readily to meet respiratory demands.
What is the role of foetal haemoglobin compared to adult haemoglobin?
Foetal haemoglobin has a higher affinity for oxygen
The dissociation curve is to the left
This allows it to extract oxygen from maternal blood effectively.
What does a leftward shift in the dissociation curve indicate?
Higher affinity for oxygen
So more O2 loads onto Hb
So saturation of Hb with O2 increases
Seen in species adapted to low oxygen environments.
What is the relationship between surface area to volume ratio and oxygen dissociation curves?
Smaller mammals lose heat more readily and have greater oxygen demands
They require haemoglobin that unloads oxygen more easily.
What effect does temperature have on haemoglobin’s affinity for oxygen?
Higher temperatures decrease haemoglobin’s affinity for oxygen
This facilitates oxygen unloading during increased metabolism.
What is the structure of Haemoglobin?
Globular protein with Quaternary Structure
Composed of four polypeptide chains, each containing a haem group
When oxygen combines with haemoglobin, what is formed?
Oxyhaemoglobin
What is the formula of calculating the percentage saturation of haemoglobin with oxygen?
(Oxygen bound to haemoglobin / Maximum Oxygen capacity of haemoglobin) x 100
What does lower pO2 mean?
Less haemoglobin is saturated
What does higher pO2 indicate?
More O2 is loaded onto Hb
Higher saturation of Hb ith O2
Why does the Hb sigmoid curve have this shape?
PROTEINS OFTEN CHANGE SHAPE WHEN THEY BIND TO OTHER SUBSTANCES
The first O2 molecule alters the tertiary structure of the Hb molecule.
This exposes the 2nd and 3rd O2 BINDING sites.
This makes it EASIER for 2nd & 3rd O2 molecules to bind & load.
After the 3rd O2 molecule binds, it is difficult for the 4th to load because the Hb is almost full
pO2 in lungs
The partial pressure of O2 (pO2) is highest
Hb has a higher affinity for O2 at a high pO2.
Haemoglobin becomes (almost) fully saturated
pO2 in respiring tissues
The pO2 in the tissue capillaries is LOWER
Haemoglobin now has a lower affinity for O2 at a lower pO2
so the oxyhaemoglobin starts to break down and unloads oxygen.
What happens when there is higher-than-normal pCO2?
Haemoglobins affinity for Oxygen is even lower.
If pCO2 increase the saturation of haemoglobin decreases.
This causes the haemoglobin-oxygen dissociation curve to shift to the right
What is the Bohr shift?
In higher-than-normal pCO2 Haemoglobins affinity for Oxygen is even lower.
If pCO2 increase the saturation of haemoglobin decreases.
This causes the haemoglobin-oxygen dissociation curve to shift to the right
Why does Hb has a lower affinity to O2 at higher levels of CO2?
When CO2 dissolves in the blood it makes the blood more acidic, thus lowering the pH.
As Hb is a protein, a change in pH slightly alters its tertiary structure.
What happens the more that tissue cells respire?
The more that tissue cells respire, the more the carbon dioxide concentration will increase and cause a shift to the right in the oxyhaemoglobin dissociation curve.
· Hb now has a lower affinity to oxygen at the respiring cells.
· As a result, more oxygen is unloaded from the haemoglobin, at the same pO2, as it becomes less saturated.
· MORE oxygen is now available to meet the oxygen demands of the respiring cells
Why would the tissue cells respire MORE?
Because of exercise
What does dissolved CO2 do?
Makes the blood more acidic
Changes the tertiary structure of Hb
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 haemoglobins. (5)
Smaller mammal has a larger surface area to volume ratio;
So more heat lost;
Larger SA:Vol ratio animals have a greater rate of respiration;
Oxygen is required for aerobic respiration;
So Haemoglobin unloads more oxygen because haemoglobin has lower affinity;
Which organisms have a form of haemoglobin where the dissociation curve is shifted to the left?
Species that live in places of lower pO2:
High altitudes
Bottom of lakes
Underground
Lug worms
OR
Human foetus
Why does the dissociation curve shift to the left in some species?
Environmental pO2 is lower
their Hb has a higher affinity for O2
Hb has a higher saturation at a lower pO2
So Hb rapidly unloads O2 when the Hb passes into the tissues
Which animals have a form of haemoglobin that has a curve shifted to the right?
Species with a high metabolic rate.
So very active animals like cheetahs or small mice because they have a larger SA:V
Why does the dissociation curve shift to the right in some species?
They respire a lot more so more O2 is required
so
Hb has a lower affinity for O2
So O2 unloads from the Hb more readily
O2 is more readily available to respiring tissues
Explain how oxygen is loaded, transported and unloaded in the blood. (6)
- Haemoglobin has a high affinity for oxygen
- In red blood cells;
- Loading in lungs;
- at high p.O2;
- Unloads to respiring tissues;
- at low p.O2;
- Unloading linked to higher carbon dioxide concentration;
Explain how an arteriole can reduce the blood flow into capillaries
Muscle contracts
Which narrows the lumen
