Overview
This lecture covers the structure and function of proteins in living organisms, emphasizing their building blocks, organization, and diverse biological roles.
Protein Structure Basics
- Proteins are macromolecules primarily made of carbon, hydrogen, oxygen, and nitrogen.
- The basic subunits of proteins are amino acids; there are 20 main amino acids in living organisms.
- All amino acids share a basic structure with a carboxyl group, amino group, and a variable R group (sidechain).
- Amino acids differ by their R group, making them polar, nonpolar, charged, or aromatic.
- Amino acids link via peptide bonds to form polypeptide chains.
- Polypeptide chains fold and may combine with other proteins to create complex structures.
Protein Function
- Proteins are essential to cell function and are often called the building blocks of life.
- Hemoglobin is a protein in red blood cells that transports oxygen; it consists of four protein subunits, each with an iron-containing heme group.
- Enzymes are proteins that speed up chemical reactions, such as lactase breaking down lactose.
- Proteins participate in metabolic pathways, genetic functions (transcription and translation), and cell signaling.
- The cytoskeleton, which maintains cell structure, is made of proteins.
- Proteins transport materials within and between cells.
- Muscle movement relies on proteins densely packed in muscle cells.
- Antibodies (immune response) and hormones (body communication) are also proteins.
Key Terms & Definitions
- Amino acid — basic building block of proteins, with a carboxyl group, amino group, and unique R group.
- Peptide bond — chemical bond linking amino acids into polypeptide chains.
- Polypeptide chain — long chain of amino acids forming part of a protein.
- Enzyme — protein that catalyzes (speeds up) chemical reactions.
- Hemoglobin — protein in red blood cells that carries oxygen.
- Cytoskeleton — network of protein fibers that gives cells shape and structure.
- Antibody — protein involved in immune defense.
- Hormone — protein or peptide that acts as a chemical messenger in the body.
Action Items / Next Steps
- Review the 20 main amino acids and their properties.
- Study how polypeptide chains fold into functional proteins.
- Learn specific examples of protein functions in cells.