🧬AP Biology
4. Hemoglobin is a complex protein found in red blood cells that is responsible for transporting oxygen throughout the body. It is a globular protein composed of four polypeptide subunits: two alpha chains and two beta chains. The function of hemoglobin depends heavily on its specific three-dimensional shape and its ability to remain soluble in the water-rich cytoplasm of the red blood cell.
The specific sequence of amino acids in each polypeptide chain dictates how the chain folds. Interactions between the side chains (R-groups) of these amino acids stabilize the protein's structure at various levels. The environment surrounding the protein, which is primarily water, also plays a critical role in determining the final conformation of the protein.
Describe the role of the R-groups of amino acids in the formation of the tertiary structure of a protein.
Explain how the polarity of water molecules influences the arrangement of amino acids in a soluble protein like hemoglobin.
In individuals with sickle cell anemia, a specific mutation in the DNA results in the substitution of the amino acid glutamic acid with valine at the sixth position of the beta-globin chain. Glutamic acid has a polar, negatively charged R-group, while valine has a nonpolar, hydrophobic R-group. This substitution occurs on the exterior surface of the hemoglobin molecule.
Predict the effect of the glutamic acid to valine substitution on the interactions between hemoglobin molecules in the aqueous cytoplasm.
Justify your prediction in part C.
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