Bài giảng Hóa sinh đại cương - Chương 1: Protein

Proteins are fundamental macromolecules, derived from the Greek word meaning "first" or "most important," underscoring their indispensable role in all biological systems. These complex polymers are constructed from repeating amino acid units linked by peptide bonds, exhibiting remarkable diversity in structure and function. Understanding protein chemistry is crucial as they serve as the primary machinery for life, mediating vital processes from catalysis and transport to structural support and defense. This introductory overview establishes the foundational context for exploring the multifaceted nature and profound significance of proteins in biological and biochemical sciences.

Sinh viên ngành sinh hóa, y học, dược học, công nghệ sinh học, và dinh dưỡng, cũng như các nhà nghiên cứu quan tâm đến cấu trúc và chức năng của protein.

Proteins, derived from the Greek term signifying "first" or "most important," are essential organic macromolecules forming complex polymers from alpha-amino acids linked by peptide bonds. Chemically, they are defined as polypeptide chains that are generally insoluble in 10% TCA. Philosophically, proteins embody the very essence of life, performing a vast array of biological functions. These functions include catalysis (as enzymes), transport (e.g., hemoglobin, lipoprotein, transferrin), structural support (e.g., collagen, elastin, keratin, fibroid), movement (e.g., actin, myosin), protection (e.g., antibody), regulation (e.g., hormones like insulin and glucagon), and providing nutrition and energy storage.

Proteins are sourced from both animal (meat, fish, eggs, milk) and plant (legumes, oilseeds) origins, and their elemental composition, notably nitrogen content, is critical for determining Crude Protein via methods like Kjeldahl. The fundamental building blocks, amino acids, are classified based on their structure, the polarity of their R-groups, and nutritional importance (e.g., essential amino acids which cannot be synthesized by the body and must be supplied through diet, versus nonessential ones). Amino acids exhibit unique chemical properties, including optical isomerism (due to a chiral carbon, except Glycine), and amphoteric behavior, acting as both acids and bases. In solution, they exist as zwitterions or internal salts. Their ionization state is pH-dependent, and the isoelectric point (pI) is a specific pH at which an amino acid carries no net electrical charge. The formation of peptides, the primary structure of proteins, involves the condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing a water molecule. This comprehensive understanding of protein structure and function is vital for various scientific disciplines.