Which five statements about hemoglobin and myoglobin structure are true? heme is composed of an organic protoporphyrin component and a metal atom. both hemoglobin and myoglobin contain a prosthetic group called heme, which contains a central iron atom. each hemoglobin molecule can bind four oxygen molecules; each myoglobin can bind only one oxygen molecule. hemoglobin and myoglobin are heterotetramers. each iron atom can form six coordination bonds. two of these bonds are formed between iron and oxygen. molecular oxygen binds reversibly to fe2+fe2+ in heme. by itself, heme is not a good oxygen carrier. it must be part of a larger protein to prevent oxidati