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

Hemoglobin demonstrates a sigmoidal oxygen dissociation curve because of cooperative binding and the binding of oxygen with the molecule of iron takes place reversibly in heme. The binding of the initial oxygen makes conformation changes in hemoglobin, increasing the further combination of additional oxygen.  

Myoglobin refers to oxygen and iron-binding monomeric protein found in the tissues of the muscles of almost all the mammals. The molecule of myoglobin comprises a solitary heme prosthetic group-administered into a hydrophobic cleft in the protein and therefore, myoglobin can reversibly combine with a single molecule of oxygen. Because of its greater affinity for oxygen, myoglobin demonstrates a hyperbolic oxygen dissociation curve and possesses a simple pattern of binding.  

The following are the true statements:  

1. Heme is not a good oxygen carrier by itself, it must be a component of a larger protein to inhibit oxidation of the iron atom.  

2. Heme comprises an organic protoporphyrin constituent and a metal atom.  

3. Both myoglobin and hemoglobin comprise a prosthetic group known as heme that comprises a central iron atom.  

4. Myoglobin is a monomer, while hemoglobin is a heterotetramer.  

5. A molecule of oxygen combines reversibly with the iron (Fe2+) in heme.  

i'd say that the moon rock is about 2.2 billion years old.