This lecture focuses on proteins, their structures, functions, and the engineering processes involved in utilizing them. It begins with an introduction to proteins as essential biomolecules composed of amino acids, highlighting their diverse roles in biological systems, including enzymes, antibodies, and structural components. The instructor discusses the necessity of dietary proteins for human health, emphasizing that the body cannot store proteins and must continuously obtain them from food. The lecture then delves into the classification of proteins into seven types based on their functions. Following this, the instructor explains the process of protein synthesis, detailing how ribosomes translate mRNA into polypeptide chains. The lecture also covers the differences between natural protein synthesis and laboratory methods, such as solid-phase peptide synthesis (SPPS), which is used to create peptides in a controlled environment. The session concludes with a discussion on the secondary structures of proteins, including alpha helices and beta sheets, and how these structures can be engineered for various applications in biotechnology and medicine.