Haemocyanin

Part of speech: noun

Definitions

1. A protein containing copper, present in the blood of certain invertebrates, functions primarily as an oxygen carrier that enhances respiratory efficiency
2. This molecule, rich in copper, serves as a vital oxygen transport agent in the circulatory systems of various arthropods and mollusks
3. A copper-based protein found in the blood of certain invertebrates, it plays a crucial role in transporting oxygen within their circulatory systems

Etymology: Haemocyanin is a compound built from three parts, each with its own story. The first, "haemo-", comes from Ancient Greek "haima" (blood), so the word is literally a "blood-blue" substance. The second, "cyan", comes from Ancient Greek "kyanos", a dark blue. The final "-in" is the suffix chemists use for a protein or other organic substance. Together they describe a protein that makes the blood of certain animals blue, rather than the red of human blood. The colour comes from copper. Where haemoglobin carries oxygen using iron and gives human blood its red tint, haemocyanin binds oxygen with copper atoms, and when oxygenated it turns the blue-green shade that gives the molecule its name. Snails, octopuses, crabs and lobsters all rely on it, which is why their blood looks blue when exposed to air.