Question 6

Define a buffer (25% of marks). Describe how acid and base shifts in the blood are buffered (75% of marks).

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College Answer

Few candidates defined a buffer making it difficult to award 25% of the marks for this question. The three main buffers in blood should have been described: bicarbonate system, haemoglobin and proteins. The pKa, the buffering mechanism and the capacity of the system should have been described. The Henderson Hasselbach equation was sometimes incorrect. Marks were only awarded for buffers in blood and unfortunately some candidates described non-blood buffers.