Question

See the side chain of the amino acid isoleucine on page 113 of your textbook. This side chain contains three methyl groups. In a folded protein in aqueous solution, an isoleucine residue is most likely to be found

A. On the surface of the protein, forming hydrogen bonds with water molecules

B. On the surface of the protein, paired with another amino acid in an ionic bond

C. In the interior of the protein, hydrogen bonded to other groups

D. In the interior of the protein, paired with another amino acid in an ionic bond

E. In the interior of the protein due to hydrophobic forces

2.Why do we need hemoglobin to transport oxygen in the bloodstream, but no protein is required to transport carbon dioxide in the blood from the tissues to the lungs?

A. carbon dioxide is hydrophilic, and can interact with water molecules in the blood, but oxygen cannot

B. the bonds in carbon dioxide are nonpolar covalent bonds, but the bonds in oxygen are polar bonds

C. carbon dioxide is surrounded by a shell of sodium ions in the bloodstream, but oxygen is not

D. oxygen is hydrophilic, and can form hydrogen bonds with water molecules in the blood, but carbon dioxide cannot

E. carbon dioxide is amphiphilic, allowing it to form micelles in the blood, but hydrophobic oxygen cannot do this

Answer 1

Answer 1- The right option is- E. In the interior of the protein due to hydrophobic forces. This is because isoleucine is a nonpolar amino acid, which means that it is hydrophobic.

Answer 2- The right option is- D. Oxygen is hydrophilic and can form hydrogen bonds with water molecules in the blood, but carbon dioxide cannot.