Question

45. Still on the topic of CO, would you expect this gas to be deadly to a cockroach in the same way it is for us? Explain why or why not?

Answer 1

The hemolymph in coackroaches contains hemocyanin, a copper-based protein that turns blue when oxygenated. This gives the hemolymph a blue-green color. In humans, the iron-based protein hemoglobin has the function of transporting oxygen. Hemocyanin binds only 1 CO per two 2 Cu centers even though the two copper centers are identical ^[1]. It has been observed that cockroaches have survived for weeks in an atmosphere of 80% carbon monoxide and 20% oxygen. Carbon monoxide has 210 times greater affinity for haemoglobin than oxygen. When, carbon monoxide poisoning occurs in humans, the CO displaces oxygen. This leads to cellular hypoxia. The toxicity of CO on an organism depends on the number of cells and size of the animal. The human body has an estimated 37.2 trillion cells. Deprivation of oxygen will have a more toxic effect on humans as they are much larger and large and more complex.

1. Sorrell TN, Jameson DL. An explanation for the observed stoichiometry of carbon monoxide binding to hemocyanin. J Am Chem Soc 1982;104:2053–4.