Overview
This lecture covers the structure, composition, and function of proteins, detailing how amino acids form proteins and their roles in the human body.
Protein Structure and Composition
- Proteins are macromolecules composed of carbon, hydrogen, oxygen, and nitrogen atoms.
- The basic subunit (monomer) of a protein is the amino acid.
- Each amino acid contains an amine group (NHâ‚‚), a carboxyl group (COOH), and a unique functional group.
- Proteins are formed when amino acids join via peptide bonds through dehydration synthesis (removal of water).
- A long chain of amino acids linked together is called a polypeptide.
Amino Acids
- There are 20 different amino acids found in proteins.
- The functional group attached to each amino acid determines its unique properties and behavior.
- Essential amino acids cannot be synthesized by the body and must be obtained from the diet.
- Functional groups can be hydrophobic (repel water), hydrophilic (attract water), acidic, basic, positively charged, or negatively charged.
Protein Folding and Function
- Functional groups cause polypeptide chains to fold into specific 3D shapes (quaternary structures).
- The folding is influenced by attraction or repulsion between different functional groups (e.g., positive vs. negative, hydrophobic vs. hydrophilic).
- The 3D structure of a protein determines its function in the body.
- Proteins serve as enzymes, receptors, transporters, and structural components.
- Mutations that change even a single amino acid can alter protein folding and disrupt its function.
Key Terms & Definitions
- Protein — A large, complex molecule made of one or more folded polypeptide chains.
- Amino acid — The monomer unit of proteins, containing an amine group, carboxyl group, and a side functional group.
- Peptide bond — The covalent bond formed between two amino acids during protein synthesis.
- Polypeptide — A chain of amino acids linked by peptide bonds.
- Essential amino acids — Amino acids that must be acquired through diet as the body cannot synthesize them.
- Functional group — The variable side group that gives each amino acid its unique properties.
Action Items / Next Steps
- Review the structure of amino acids and how peptide bonds form.
- Memorize the essential amino acids.
- Prepare for questions on how protein structure relates to function and effects of mutations.