Haemoglobin Flashcards
(21 cards)
What is the function of haemoglobin
Transporting oxygen around the body to deliver them to the cells
Describe the structure of haemoglobin
Haemoglobin is a protein with a quaternary structure (one haemoglobin molecule is made of 4 polypeptide chains- 2 alpha and 2 beta).
Haemoglobin is split into 4 subunits, each containing a haem group at it’s centre. Each haem group contains an iron ion which can bind reversibly with oxygen.
How many oxygen molecules can a haemoglobin bind to and why
4, as it has 4 haem groups and each haem group can bind reversibly to one molecule of oxygen
Give 3 structural features of a red blood cell and how they are useful
Biconcave shape - this increases the surface area:volume ratio to enable oxygen to diffuse into the cell more quickly
No nucleus - this makes more space for haemoglobin, so more oxygen can be carried at once
Thin, giving it a short diffusion distance for oxygen to enter and leave the cell
What is formed when haemoglobin binds to oxygen
Oxyhaemoglobin
Define partial pressure
The amount of a particular gas in a mixture of gases or a solution
What is partial pressure of oxygen measured in
kPa (kilo pascals)
What type of curve is used to show the loading and unloading of oxygen at different partial pressures
The oxygen dissociation curve which is a sigmoid shape
Define loading
When oxygen is taken up by haemoglobin
Define unloading
When oxygen is released by haemoglobin
What has a higher affinity for oxygen: adult haemoglobin or fetal haemoglobin
Fetal haemoglobin
Explain the oxygen dissociation curve
Initially, as the partial pressure of oxygen increases, the percentage saturation of haemoglobin with oxygen increases slowly. However, as the partial pressure of oxygen continues to increase, the percentage saturation of haemoglobin with oxygen increases rapidly - this is due to cooperative bonding.
PO2 in tissues when at rest:
Because there’s a lower partial pressure of oxygen, the haemoglobin has a low affinity for oxygen and it unloads more readily. This means the haemoglobin has a lower percentage saturation of haemoglobin
PO2 in the lungs:
As there’s a higher partial pressure of oxygen in the lungs, the haemoglobin has a high affinity for oxygen. This means it loads oxygen more readily, giving a higher % saturation of haemoglobin.
Explain the affinity for oxygen at the tissues
Because there’s a lower partial pressure of oxygen, the haemoglobin has a low affinity for oxygen and it unloads more readily. This means the haemoglobin has a l
Outline how cooperative bonding works. Explain how this is shown in the ODC and how it is useful to us.
The binding of one molecule of oxygen to haemoglobin makes it easier for the second to bind:
When the first oxygen binds to the haemoglobin, this causes a change in the tertiary structure. This change allows more oxygen to bind more easily as it uncovers other binding sites (the haem groups containing the iron ions) for oxygen to bind to. This means after the first oxygen binds, it’s easier for the haemoglobin to become more saturated with oxygen.
This can be seen in the ODC, as at a low partial pressure of oxygen, there is a little increase in the saturation of haemoglobin as oxygen increases. There is then a rapid rise in saturation after the first oxygen binds, as it gets easier for oxygen to bind.
The advantage of this is it ensured a rapid loading of oxygen in the lungs (at high pp02), and rapid unloading of oxygen at the tissues (at low pp02).
Explain the Bohr shift and what impact it has (how it’s useful)
This is the effect of CO2 concentration on the dissociation of oxyhaemoglobin.
As cells respire, they release CO2 which dissolves in the blood to form carbonic acid. This results in a decrease in the pH, and as haemoglobin is a protein, this will alter the shape of the haemoglobin and decrease its affinity to oxygen. This causes the oxygen dissociation curve to shift to the right, and this is known as the Bohr shift.
This causes the haemoglobin to dissociate and unload oxygen more readily at the tissues- this means more oxygen will be delivered to the respiring cells, for a higher rate of respiration.
During exercise, this is useful as the cells will be respiring more and producing more CO2, but there will be a low ppO2- this shift will allow more oxygen to dissociate and be unloaded to the respiring tissues for use in aerobic respiration.
Explain how active animals haemoglobin will be adapted
They are likely to have ODCs that have shifted to the right, meaning their haemoglobin has a lower affinity for oxygen.
This means the haemoglobin dissociates and unloads oxygen more readily, releasing more oxygen to the cells to allow for higher rates of respiration - this causes more energy to be released.
Explain how foetal haemoglobin is adapted
Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin. This means oxygen is more readily unloaded by adult haemoglobin, so it can diffuse across the placenta, and is loaded more readily by the foetal haemoglobin. This oxygen can then be used by the foetus for aerobic respiration.
Explain how the haemoglobin of small animals is adapted
Because they have large surface area to volume ratios, they will lose heat more quickly per gram of body mass than larger organisms.
It’s haemoglobin has a lower affinity for oxygen, so more oxygen can be dissociated and unloaded for aerobic respiration - this will release heat energy to maintain their body temperature
Explain how the ODC of humans may differ from that of an animal that lives underwater
Because there’s a lower partial pressure of oxygen underwater, the Underwater animals haemoglobin will be a different shape.
This causes their ODC to shift to the left, so their haemoglobin has a higher affinity for O2.
This means they more readily load oxygen, so become fully saturated at lower ppO2.
What part of the red blood cell contains the haemoglobin
The erythrocytes
In basic terms, how does a higher pH effect haemoglobin
It increases the affinity
