Final answer:
Each hemoglobin molecule is composed of four polypeptide chains: two alpha and two beta chains, making the statement true. These polypeptide chains fold to accommodate a heme group each, allowing hemoglobin to transport oxygen efficiently within the bloodstream.
Step-by-step explanation:
The statement that each hemoglobin molecule has four polypeptide chains is true. These chains are two alpha (alpha) chains and two beta (beta) chains, each playing a critical role in the function and structure of hemoglobin. The alpha chains consist of 141 amino acids each, while the beta chains have 146 amino acids.
The precise sequence of these amino acids and the characteristic folding of the hemoglobin molecule allow each polypeptide chain to form a pocket-like structure that houses a heme group. With four heme groups in total, each containing iron, hemoglobin can bind up to four oxygen molecules, facilitating vital oxygen transport in the bloodstream.
Different forms of hemoglobin exist, such as HbA in normal adult human beings with 2 alpha and 2 beta chains, HbA₂ with 2 alpha and 2 delta chains, and HbF, the fetal hemoglobin, with 2 alpha and 2 gamma chains. This variation allows for different oxygen-carrying capacities, which are essential during different stages of human development.