Amino Acids

1°, 2°, 3°, and 4° structure of proteins

• 1° structure linkage is the peptide bond between amino acids
• 2° structure is the local folding of the polypeptide chain into alpha helices and beta sheets, stabilized by hydrogen bonds.
• 3° structure is the overall 3D shape of a protein, determined by interactions between R groups, including hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bridges.
• 4° structure is the assembly of multiple polypeptide subunits into a functional protein complex, stabilized by the same interactions as 3° structure.

Amino Acid Properties

• Nonpolar amino acids have hydrophobic side chains that do not interact favorably with water.
• Polar amino acids have side chains that can form hydrogen bonds with water, making them hydrophilic.
• Charged amino acids have side chains that can gain or lose protons, resulting in positive or negative charges at physiological pH.

Protein Structure and Function

• Protein folding is driven by the hydrophobic effect, where nonpolar side chains cluster away from water, and polar side chains interact with the aqueous environment
• Cysteine can form disulfide bonds, which are covalent linkages that stabilize protein structure.
• Proline introduces kinks in the polypeptide chain, affecting overall folding
• Conformational stability of proteins is influenced by factors such as pH and temperature.
• Denaturation is the loss of protein structure and function due to factors like heat, pH changes, or chemical agents
• Hydrophobic interactions play a crucial role in protein folding and stability, as nonpolar side chains tend to avoid contact with water, driving the folding process.