例句與造句

1. Four molecules of porphobilinogen combine to form a linear tetrapyrrole, which cyclizes to uroporphyrinogen III . Oxidation and side-chain modifications lead to the synthesis of protoporphyrin IX, which acquires an iron atom to form heme.
2. It's difficult to find linear tetrapyrrole in a sentence. 用linear tetrapyrrole造句挺難的