Which of the biomolecules below includes a polydentate ligand called a porphyrin? hemoglobin chlorophyll cytochrome c carbonic anhydrase?

The correct answer is haemoglobin.
Porphyrins are a group of heterocyclic macrocycle organic compounds with the function to absorb strongly in the visible region of the electromagnetic spectrum. Those molecules are composed of four modified pyrrole subunits connected with carbon atoms. Porphyrins are the conjugate acids of ligands. They bind metals, like iron to form complex- heme which is the component of haemoglobin.