What chemical element gives the blood of a lobster a bluish tint?
The blood of a lobster is generally colorless until it is exposed to oxygen. The bluish tint comes from hemocyanin, which is similar to the blood of snails and spiders but contains copper instead of iron.
Hemocyanin is found in crustaceans and mollusks like lobsters, shrimps and crabs.
It is used to carry oxygen around the body so that the blood can return from cells back to the lungs to be refilled with it. It also allows the body to stay hydrated and healthy.
Vertebrates, including humans, have blood that is red because of the presence of oxyhemoglobin. This is a compound that carries oxygen through the blood, and also combines with iron to make compounds called hemoglobin.
A few other things can give blood a bluish tint, too:
Lycopene and canthaxanthin produce the pink colors of tomatoes, guava, red grapefruit, papaya, rosehips, watermelon, salmon and trout. They are also used as food coloring and as a tanning aid in live animals.
Astaxanthin, on the other hand, produces the red colors of cooked salmon, red bream, trout and lobster. It is also used to ensure captive flamingos keep their coloring.
In this study, we have shown that the structural basis for the bathochromic shift of the carotenoprotein b-CR has been established. The molecular replacement search has enabled us to deduce the amino acids and protein contacts that are essential for the binding of the carotenoid astaxanthin (AXT) and the protein multimacromolecular complex crustacyanin (CR). This work provides new insights into how a broad range of invertebrate carotenoproteins regulate coloration through AXT.