Overview
This lecture introduces the four major biological macromolecules—carbohydrates, proteins, lipids, and nucleic acids—and explains their structure, function, and importance in living organisms.
Macromolecules: General Concepts
- Macromolecules are large organic molecules (biomolecules) that make up living things.
- They are polymers, built by linking together smaller units called monomers.
Carbohydrates
- Carbohydrates (sugars) can be simple (one or two units) or complex (many units).
- Simple carbohydrates: one sugar (monosaccharide, e.g., glucose, fructose) or two joined (disaccharide, e.g., sucrose, lactose).
- Complex carbohydrates: many sugars linked (polysaccharide, e.g., starch, glycogen, cellulose).
- Skeletal formulas use lines for bonds, bends/ends for carbons, and show ring structures for sugars.
Proteins
- Proteins are polymers made of 20 types of amino acid monomers.
- Amino acids connect via peptide bonds; two form a dipeptide, three a tripeptide, many a polypeptide.
- When polypeptide chains reach 50–100 amino acids, they are folded into a functional protein.
- Amino acids have a central carbon, amine group (NH2), carboxylic acid group (COOH), hydrogen, and an R group (which varies among amino acids).
Lipids
- Lipids include fats and oils, collectively called triglycerides.
- Triglycerides consist of one glycerol molecule and three fatty acids.
- Lipids are nonpolar (hydrophobic) and do not mix with water.
- Fats are usually solid at room temperature (animal origin, saturated fatty acids), while oils are liquid (plant origin, unsaturated fatty acids).
- Saturated fats have no double bonds in fatty acid chains; unsaturated fats have one or more double bonds causing kinks.
Nucleic Acids
- Nucleic acids (DNA and RNA) are polymers of nucleotide monomers.
- Nucleotides include adenine (A), thymine (T), guanine (G), cytosine (C), and uracil (U).
- DNA stands for deoxyribonucleic acid; RNA stands for ribonucleic acid.
Lab Safety and Procedures
- Clean test tubes using a brush and soap, rinse thoroughly, and place upside down to dry.
- Clean the workstation with a wet paper towel.
- Avoid cross-contaminating pipets between tests to prevent false results.
- Wear safety goggles; handle hot plates, stains, and broken glass carefully.
- Familiarize yourself with indicator stains listed on page 5 of the lab manual.
Key Terms & Definitions
- Monomer — small molecular unit that can join with others to form a polymer.
- Polymer — large molecule made of repeating monomer units.
- Monosaccharide — simple sugar with one unit (e.g., glucose).
- Disaccharide — two monosaccharides joined together (e.g., sucrose).
- Polysaccharide — large carbohydrate made of many monosaccharides (e.g., starch).
- Amino Acid — monomer unit of proteins, with a central carbon and side group (R).
- Peptide Bond — bond linking amino acids in a protein chain.
- Triglyceride — lipid with one glycerol and three fatty acids.
- Saturated Fat — fatty acid with no double bonds; solid at room temp.
- Unsaturated Fat — fatty acid with double bonds; liquid at room temp.
- Nucleotide — monomer of nucleic acids, includes A, T, G, C, and U bases.
Action Items / Next Steps
- Read page 5 of the lab manual to review indicator stains.
- Review lab procedures and safety protocols before attending lab.
- Prepare to test for carbohydrates, proteins, and lipids in the upcoming lab.