CHEM2921_03 - proteins_03_ProteinStructure_1

Chapter 1: Introduction to Proteins

• Focus on protein structure and its importance in food and biology.

• Protein affects: solubility, elasticity, emulsifiers, and texture.

• Chemically, proteins are polymers with repeating biological units.

  • Example of a polymer: Styrene leading to polystyrene.

  • A biopolymer has similar repeating units that are biological.

Chapter 2: Different Amino Acids

• Amino acids form peptides (short chains) and ultimately proteins (polypeptides).

• Primary structure: linear sequence of amino acids connected by covalent bonds.

• Secondary structure: larger components formed by hydrogen bonds, including beta sheets and alpha helices.

• Tertiary structure: overarching shape of a single protein molecule.

Chapter 3: Bond to Nitrogen

• Quaternary structure: assembly of multiple protein molecules into a larger unit (e.g., enzymes, ribosomes).

• Amino acids connected through condensation reactions, forming peptide bonds.

• Peptide bond formation: carboxylic acid + amine, losing water; reversible through hydrolysis.

Chapter 4: Partial Double Bond

• Peptide bonds exhibit resonance structures, contributing to rigidity.

• Peptide bond characteristics: partial double bond prevents free rotation, affecting hydrogen bonding capability.

Chapter 5: Form of Amino Acids

• Comparison of various amino acids:

  • Glycine (simplest), hydrophilic (OH groups), charged (acidic/basics), aliphatic (hydrophobic), and aromatic (not water-friendly).

• Interactions between amino acids affect their placement in proteins based on charge and hydrophilicity.

• Representation of amino acids: full names, three-letter codes, one-letter codes.

Chapter 6: Representation of Amino Acids

• Examples of one-letter codes: A (Alanine), D (Aspartic acid), K (Lysine), L (Leucine), R (Arginine), E (Glutamic acid), G (Glycine), Q (Glutamine).

• Protein sequences represented from N-terminus to C-terminus (amino end to acid end).

Chapter 7: Conclusion

• Example of protein variant: beta-casein in milk (A1 vs A2 variant) showing importance of single amino acid changes.

• Impact of mutations (e.g., coronavirus variant D614G) on protein functionality and transmission efficiency.

• A small difference in amino acids can lead to significant physiological effects.