Overview
This lecture introduces the four biomolecule families—carbohydrates, lipids, proteins, and nucleic acids—focusing on their structure, monomers, and biological roles in living organisms.
The Four Biomolecule Families
- Biomolecules are molecules essential for life, grouped into four families: carbohydrates, lipids, proteins, and nucleic acids.
- Carbohydrates include sugars and starches found in bread, jelly, and plants; they are major energy sources.
- Lipids include fats, oils, and waxes found in peanut butter and other foods; they provide energy, insulation, and waterproofing.
- Proteins are found in foods like meat and eggs; they build structures, catalyze reactions, and support immune defenses.
- Nucleic acids, including DNA and RNA, store and transmit genetic information; not present as food.
Carbohydrates
- Carbohydrates are made from monomers called monosaccharides (simple sugars), such as glucose (C6H12O6).
- Two monosaccharides make a disaccharide (e.g., sucrose/table sugar).
- Polysaccharides are long chains of monosaccharides; starch stores energy, while cellulose provides structural support.
- Cellulose is found in plant cell walls and foods like celery and lettuce.
Lipids
- Lipids are mostly nonpolar molecules, including fats, oils, waxes, phospholipids, and steroids.
- Fats and oils are built from fatty acids and store more energy (9 calories/gram) than other foods.
- Fats provide insulation and energy storage, while waxes waterproof surfaces like plant leaves.
- Phospholipids have polar and nonpolar sides, forming cell membranes via bilayers.
- Steroids have four fused carbon rings and include hormones like testosterone and estrogen.
Proteins
- Proteins make up structures (skin, hair, muscles), catalyze reactions (enzymes), and defend against infections (antibodies).
- Protein monomers are amino acids; there are 20 types.
- Foods like meat and egg whites are rich in protein.
Nucleic Acids
- Nucleic acids include DNA (heredity molecule) and RNA, which store and transmit genetic information.
- Their monomers are nucleotides; ATP is a nucleotide important for energy transfer.
Key Terms & Definitions
- Monomer — a single building block molecule that can form larger molecules.
- Monosaccharide — simple sugar and carbohydrate monomer (e.g., glucose).
- Polysaccharide — long chain of monosaccharides (e.g., starch, cellulose).
- Fatty Acid — building block of many lipids, long hydrocarbon chain.
- Phospholipid — lipid molecule with polar and nonpolar regions; forms cell membranes.
- Steroid — lipid with four fused carbon rings; includes hormones.
- Amino Acid — protein monomer; 20 types.
- Nucleotide — nucleic acid monomer; forms DNA, RNA, ATP.
Action Items / Next Steps
- Complete the interactive concept map and quiz on the instructor's website.
- Watch four short videos and tutorials at sciencemusicvideos.com (now Learn-Biology.com) about carbon structure, functional groups, monomers/polymers, and carbohydrates.
- Subscribe to the channel and leave comments or questions.
- Prepare for the next episode on biochemistry.