Ch

HC Fe

CH2 CH2

Figure 11.6. A haemoglobin molecule.

consists of a tetrapyrrole ring, protoporphyrin IX, surrounding a single ferrous ion. Free haemoglobin, that is haemoglobin not enveloped in a red cell plasma membrane are quickly bound to haptoglobin, a plasma transport protein, but large amounts can be toxic, causing vasospasm, endothelial cell leak and renal failure. Defects in globin synthesis in the cytoplasmic ribosomes of red cell precursors result in the haemo-globinopathies and thalassaemias. Defects in haem synthesis in the mitochondria of precursor cells result in the porphyrias.

0 0

Post a comment