In biological macromolecules like proteins, the hydrophobic residues tend to clump together in the interior of the folded structure. What is the best explanation for why this occurs?
| A.Polar residues tend to bind to water in the cytoplasm as well as to each other. The water and polar residues cannot bind to the hydrophobic ones, so in the lowest energy state the hydrophobic residues are pushed together in the middle. |
| B.Hydrophobic residues bind to each other in specific ways. For instance, Ala forms di-methyl bonds, and phenylalanine binds isoleucine. This creates a tightly bound hydrophobic inner core. |
| C.Hydrophobic residues bind each other, while polar residues cannot bind each other. Therefore the hydrophobic ones end up stuck to each other in the core of the protein. |
D.Protein folding machinery interprets the amino acid code to pack hydrophobic residues into the center of proteins. This process must be important, because the cell expends large amounts of ATP to precisely coordinate protein folding.
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