Which of the following is CORRECT when considering the tertiary structure of globular proteins?

Hydrophobic residues are normally on the inside and hydrophilic residues are on the outside.

The amino acid proline never occurs in a region where the polypeptide chain bends or turns.

All parts of the proteins can be classified as helix, ?sheet or turns.

? sheets cannot be twisted or wrapped into barrel structures.

None of the above.