Haematology practicals Flashcards
Haem structure?
The haem group consists of a ferrous iron ion (Fe2+) bound by a porphyrin ring.
Each Fe2+ within haem can bind to how many oxygen molecules?
One.
What are the two gene clusters that code for the haemoglobin molecule?
Alpha and beta cluster.
What is the P50 value?
Is the pressure at which hemoglobin is 50% saturated.
Explain the shape of Oxygen–haemoglobin dissociation curve?
Sigmoid. Once one haem group binds to oxygen it is easier for other groups to bind to oxygen. This is known as positive cooperative effect.
What does 2,3 dpg do to haemoglobin?
Binds to site in deoxyhaemoglobin distant from haem groups and reduces affinity for oxygen.
How is 2,3 dpg made?
Conversion of 1,3 bpg made in glycolysis to 2,3 bpg via Rapoport- Luebering shuttle.
Why does haemoglobin F have a greater affinity that haemoglobin A?
Single amino acid substitution in gamma chain of haemoglobin F results in reduced affinity for 2,3 bpg and so increased affinity for oxygen.
Why is it important that fetal haemoglobin has a greater affinity for oxygen than haemoglobin A?
Allows for O2 to flow from maternal oxyhaemoglobin to fetal deoxyhaemoglobin.
What is the bohr effect?
H+ and CO2 production facilitates oxygen release from oxyhaemoglobin. This can be seen in exercise.
In relation to the effect on haemoglobin what are H+ ions, CO2 and 2,3dpg?
Allosteric effectors.
What are different human haemoglobin type separation based on in electrophoresis?
Charge.
What is the beer lambert law used for?
To calculate concentration of substance using absorbance value.
What is the path length in beer lambert law?
Length of cuvette.
What is the extinction coefficient in the beer lambert law?
A constant for the substance being measured at that particular wavelength.
Myoglobin key points?
Has one haem group per molecule and displays a greater affinity for oxygen than haemoglobin. However, the lack of cooperativity means that it is poor at releasing oxygen under the same conditions.
What can spectrophotometry be used for in relation to haemoglobin?
Can be used to follow changes in oxygen binding by haemoglobin - absorbance changes when oxygen is bound. Checking the respiratory status of newborn infants.
How does pulse oximetry work?
Device emits light at two wavelengths. The ratio of absorbances at each wavelength can be converted to SpO2.
What is methaemoglobin?
Is generated when the Fe2+ion is oxidised to theFe3+
In methaemoglobin patients what is the colour of blood?
Bluish/chocolate colour.
What does methaemoglobin do to the oxygen dissociation curve? What does this result in?
Shift leftwards, which can result in tissue anoxia, as oxygen is not readily released by MetHb.
What causes methaemoglobin to be present in blood?
Lack of methemoglobin reductase or production of a mutant form of haemoglobin known as haemoglobin M, which isresistant to reduction. Exposure to chemicals such as p-chloroaniline, nitrates, and local anaesthetics such as benzocaine.
Why does haemoglobin A travel further in electrophoresis that haemoglobin S?
HbA is more negatively charged than HbS.Due to a point mutation occurring in one amino acid of the β-chain. In this mutation, the amino acid glutamate in the normal protein (hydrophilic, negatively charged) is replaced by valine (hydrophobic, uncharged).
In someone who is heterozygous for sickle cell disease what would you see on the electrophoresis gel?
Both HbA and HbS bands for that individual.
