Function of Haemoglobin in Oxygen Carriage Flashcards
Regarding genetic defects in haemoglobin (true or false):
Genetic defects in haemoglobin are the least common of all genetic disorders
False. Genetic defects in haemoglobin are the most common of all genetic disorders.
Regarding genetic defects in haemoglobin (true or false):
Sickle cell disease is caused by a single base mutation in the β globin gene
True
Regarding genetic defects in haemoglobin (true or false):
Normally equal quantities of α and β chains are produced
True. A problem with either the α or β globin gene leads to an excess of one type of chain being produced. Excess globin chains precipitate causing haemolysis and anaemia.
Regarding genetic defects in haemoglobin (true or false):
α-thalassaemia is usually due to deletions of one or more α genes
True. This has varying degrees of clinical severity. 4-gene deletion is incompatible with life.
Regarding genetic defects in haemoglobin (true or false):
β-thalassaemia is most often apparent at birth
False. β-thalassaemia usually becomes apparent at between three to six months of age, when the switch to adult HbA takes place.
Regarding haemoglobin (true or false):
Each haem binds to one iron atom
True
Regarding haemoglobin (true or false):
Each haemoglobin molecule carries two oxygen molecules
False. One haem group binds reversibly to one molecule of oxygen, so each haemoglobin molecule binds four oxygen molecules
Regarding haemoglobin (true or false):
Methaemoglobin formation is due to oxidation of Fe3+ to Fe2+
False. Iron can be oxidized from the ferrous (Fe2+) to the ferric (Fe3+) form. As Fe3+ it is unable to combine with oxygen. Methaemoglobin is an oxidized derivative of hemoglobin.
Regarding haemoglobin (true or false):
2,3-DPG binds to the β-chains of haemoglobin
True
Regarding haemoglobin (true or false):
The presence of carboxyhaemoglobin increases the Hüfner constant
False. Hüfner’s constant is the amount of oxygen (in ml) carried by each gram of haemoglobin. Different values have been obtained for this constant, with those found experimentally consistently lower than the theoretical value. This is believed to result from the presence of small percentages of other forms of haemoglobin, such as COHb, in in-vivo samples.
The oxyhaemoglobin dissociation curve is shifted to the right with (true or false):
An increase in temperature
True
The oxyhaemoglobin dissociation curve is shifted to the right with (true or false):
An increase in carbon monoxide
False. CO has an affinity for haemoglobin that is 300 times that of oxygen. It shifts the oxy-haemoglobin dissociation curve to the left. The most common source of CO is tobacco smoke.
The oxyhaemoglobin dissociation curve is shifted to the right with (true or false):
An increase in 2,3-DPG
True
The oxyhaemoglobin dissociation curve is shifted to the right with (true or false):
Fetal haemoglobin
False. HbF has a greater affinity for O2 than HbA.
The oxyhaemoglobin dissociation curve is shifted to the right with (true or false):
Anaemia
True
Regarding investigations into, and manufacture of, alternative means of O2 delivery (true or false):
Perfluorocarbons promise to provide an alternative means of oxygen delivery
False. Perfluorocarbons were investigated. However, while initial results seemed promising, this research has been abandoned because of adverse effects caused by the emulsified perfluorocarbon preparation required for clinical use.
Regarding investigations into, and manufacture of, alternative means of O2 delivery (true or false):
Using stroma-free haemoglobin extracted from erythrocytes is problematic because Hb dissociates into α/β dimers after extraction
True. α/β dimers are non-functional and can cause nephrotoxicity.
Regarding investigations into, and manufacture of, alternative means of O2 delivery (true or false):
Genetic engineering techniques have been used to produce large quantities of stabilized haemoglobin
True. Genetic engineering techniques have been used to insert a modified haemoglobin gene into E.coli plasmids, which then produce stabilized haemoglobin in large quantities.
Regarding investigations into, and manufacture of, alternative means of O2 delivery (true or false):
Free haemoglobin has a much shorter intravascular half-life than an erythrocyte
True. This can lead to raised bilirubin levels. Free haemoglobin is also an excellent scavenger of nitric oxide and the resulting vasoconstriction may be the cause of hypertension seen in some phase 1 clinical trials.
