Overview
This lecture covers the major categories of biomolecules—carbohydrates, proteins, lipids, and nucleic acids—their structures, functions, and importance in living organisms.
Biomolecules: Introduction & Classification
- Biomolecules are organic compounds produced by living organisms and are essential for life.
- The four major classes are carbohydrates, lipids, proteins, and nucleic acids.
- All biomolecules contain carbon, making them organic.
- Monomers (single units) link together to form polymers (many units).
- Biomolecules can be macromolecules (large, e.g., proteins) or micromolecules (small, e.g., sugars).
Carbohydrates
- Carbohydrates (saccharides/carbs) provide energy; each gram yields 4 calories.
- Their general formula is (CHâ‚‚O)n, showing a carbon:hydrogen:oxygen ratio of 1:2:1.
- Functions: main energy source, stored fuel, intermediates in biosynthesis, regulate nerve/brain function, and dietary fiber aids digestion.
- Types:
- Monosaccharides: single sugars (glucose, fructose, galactose).
- Disaccharides: two monosaccharides (sucrose, lactose, maltose).
- Polysaccharides: many monosaccharides (starch in plants, glycogen in animals, cellulose for plant structure and dietary fiber).
Proteins
- Proteins (polypeptides) are polymers of amino acids and serve structural, enzymatic, and regulatory roles.
- Composed of carbon, hydrogen, oxygen, nitrogen, and sulfur.
- Essential amino acids (9) must come from the diet; others are synthesized by the body.
- Functions: structure (hair, nails), enzymes (catalysts), transport, immune defense, and hormones.
Lipids
- Lipids store energy, form cell membranes, and act as hormones.
- Hydrophobic (water-insoluble), made of carbon, hydrogen, and oxygen.
- Types:
- Fatty acids: saturated (solid, no double bonds, animal sources) and unsaturated (liquid, double bonds, plant sources).
- Triglycerides: fats (solid) and oils (liquid).
- Steroids: include hormones (cholesterol is a key example).
- Waxes: protective coatings for plants and animals.
Nucleic Acids
- Nucleic acids (DNA and RNA) store and transmit genetic information.
- Made of nucleotides: phosphate group, five-carbon sugar, and nitrogenous base.
- DNA is the blueprint for proteins; RNA helps in protein synthesis.
- Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.
Key Terms & Definitions
- Biomolecule — An organic molecule essential for life, produced by living organisms.
- Monomer — Smallest unit of a biomolecule.
- Polymer — Large molecule made from monomers.
- Macromolecule — Large, high-molecular-weight molecule (e.g., protein).
- Carbohydrate — Energy-providing biomolecule with a 1:2:1 C:H:O ratio.
- Monosaccharide — Single sugar unit.
- Disaccharide — Two monosaccharide units.
- Polysaccharide — Polymer of many sugars.
- Protein — Polymer of amino acids, vital for structure and function.
- Amino acid — Building block of proteins.
- Essential amino acid — Amino acid not synthesized by the body and obtained from diet.
- Lipid — Hydrophobic biomolecule, includes fats, oils, steroids, and waxes.
- Fatty acid — Building block of lipids.
- Nucleic acid — Polymer carrying genetic information (DNA or RNA).
- Nucleotide — Monomer of nucleic acids.
- DNA/RNA — Types of nucleic acids; DNA stores genetic info, RNA synthesizes proteins.
Action Items / Next Steps
- Review the structures and functions of each biomolecule class.
- Memorize key definitions and examples of biomolecules.
- Prepare for quiz on biomolecule types, functions, and examples.