Haematology practicals

Question 1

Haem structure?

Answer 1

The haem group consists of a ferrous iron ion (Fe2+) bound by a porphyrin ring.

Question 2

Each Fe2+ within haem can bind to how many oxygen molecules?

Answer 2

One.

Question 3

What are the two gene clusters that code for the haemoglobin molecule?

Answer 3

Alpha and beta cluster.

Question 4

What is the P50 value?

Answer 4

Is the pressure at which hemoglobin is 50% saturated.

Question 5

Explain the shape of Oxygen–haemoglobin dissociation curve?

Answer 5

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.

Question 6

What does 2,3 dpg do to haemoglobin?

Answer 6

Binds to site in deoxyhaemoglobin distant from haem groups and reduces affinity for oxygen.

Question 7

How is 2,3 dpg made?

Answer 7

Conversion of 1,3 bpg made in glycolysis to 2,3 bpg via Rapoport- Luebering shuttle.

Question 8

Why does haemoglobin F have a greater affinity that haemoglobin A?

Answer 8

Single amino acid substitution in gamma chain of haemoglobin F results in reduced affinity for 2,3 bpg and so increased affinity for oxygen.

Question 9

Why is it important that fetal haemoglobin has a greater affinity for oxygen than haemoglobin A?

Answer 9

Allows for O2 to flow from maternal oxyhaemoglobin to fetal deoxyhaemoglobin.

Question 10

What is the bohr effect?

Answer 10

H+ and CO2 production facilitates oxygen release from oxyhaemoglobin. This can be seen in exercise.

Question 11

In relation to the effect on haemoglobin what are H+ ions, CO2 and 2,3dpg?

Answer 11

Allosteric effectors.

Question 12

What are different human haemoglobin type separation based on in electrophoresis?

Answer 12

Charge.

Question 13

What is the beer lambert law used for?

Answer 13

To calculate concentration of substance using absorbance value.

Question 14

What is the path length in beer lambert law?

Answer 14

Length of cuvette.

Question 15

What is the extinction coefficient in the beer lambert law?

Answer 15

A constant for the substance being measured at that particular wavelength.

Question 16

Myoglobin key points?

Answer 16

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.

Question 17

What can spectrophotometry be used for in relation to haemoglobin?

Answer 17

Can be used to follow changes in oxygen binding by haemoglobin - absorbance changes when oxygen is bound. Checking the respiratory status of newborn infants.

Question 18

How does pulse oximetry work?

Answer 18

Device emits light at two wavelengths. The ratio of absorbances at each wavelength can be converted to SpO2.

Question 19

What is methaemoglobin?

Answer 19

Is generated when the Fe2+ion is oxidised to theFe3+

Question 20

In methaemoglobin patients what is the colour of blood?

Answer 20

Bluish/chocolate colour.

Question 21

What does methaemoglobin do to the oxygen dissociation curve? What does this result in?

Answer 21

Shift leftwards, which can result in tissue anoxia, as oxygen is not readily released by MetHb.

Question 22

What causes methaemoglobin to be present in blood?

Answer 22

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.

Question 23

Why does haemoglobin A travel further in electrophoresis that haemoglobin S?

Answer 23

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).

Question 24

In someone who is heterozygous for sickle cell disease what would you see on the electrophoresis gel?

Answer 24

Both HbA and HbS bands for that individual.

Question 25

What should graphs always have?

Answer 25

Axis titles, axis units, detailed caption and error bars (if using
averages)

Question 26

Stains used for blood film?

Answer 26

Haematoxylin and Eosin. Leishman’s stain