Hey,

Prosthetic Groups are tightly bound non proteinaceous organic compound like  heme, biotin, flavin etc.

We know that cofactors can be classified as either inorganic or organic molecules where organic is generally derived from vitamins and the coenzyme that is tightly bound is termed as prosthetic groups.

thus, the answer to your question is  prosthetic groups.

I hope this helps.

All the best!