Respiratory System Question????

Question

Select the correct statement regarding the role of respiratory pigments:

a. Respiratory pigments are proteins containing polypeptide subunits, heme groups, and cofactors, which allow for carbon dioxide and water exchange to occur.

b. Hemoglobin, a respiratory pigment found in many vertebrates, is ideal as an oxygen carrier for the respiratory system because it can bind with and transport oxygen and then release carbonic acid when needed.

c. Myoglobin, an oxygen-carrying protein found in muscles, has a lower affinity for oxygen at a given partial pressure than hemoglobin.

d. The iron atom, which is found at the center of the heme group, binds to oxygen and is responsible for the color of the pigment

Answer 1

From my current knowledge I believe the answer is B. I can't really give exact answers for why the others are not right, it just doesn't sound right. I do know thought that Oxygen binds to 4 Heme rings to cause oxygen saturation. When there is a lack of oxygen binding to hemoglobin it can cause a change of pigmentation. Iron is also in the heme group, but Fe does not bind to O2, O2 binds to heme, with Fe still being attached to heme.....Hope it helps.

Answer 2

D.

"A heme group consists of an iron (Fe) ion (charged atom) held in a heterocyclic ring, known as a porphyrin. The iron ion, which is the site of oxygen binding, bonds with the four nitrogens in the center of the ring, which all lie in one plane."

B is incorrect. Iron, the binding ion of hemoglobin, cannot bind to carbonic acid. The iron in hemoglobin can bind carbon dioxide, carbon monoxide (which, hemoglobin actually has a higher affinity for), and many other gases. Carbonic acid, however, is stored inside an RBC (Red Blood Cell), not attached to the hemoglobin. Therefore, because choice B states that hemoglobin can release carbonic acid when needed, choice B is incorrect.