Overview
This lecture reviews the four main macromolecules—proteins, carbohydrates, lipids, and nucleic acids—their structure, key functions, and related terminology, ending with a short quiz.
Proteins
- Proteins serve as enzymes, hormones, antibodies, structural support, and facilitate transport and storage in the body.
- Made up of long chains of amino acids joined in a specific sequence.
- Each amino acid has a hydrogen atom, carboxyl group, amino group, and a unique side chain (R group).
- Protein structure has four levels: primary (amino acid sequence), secondary (alpha helices/beta sheets), tertiary (3D folding), and quaternary (multiple polypeptides).
- Only some proteins, like hemoglobin, have a quaternary structure.
Carbohydrates
- Carbohydrates provide energy, store energy, support cell structures, and are parts of DNA/RNA.
- Made of carbon, hydrogen, and oxygen in a 1:2:1 ratio.
- Monosaccharides are simple sugars (e.g., glucose, fructose).
- Disaccharides are two monosaccharides joined (e.g., sucrose, lactose).
- Polysaccharides are hundreds of monosaccharides linked (e.g., starch, glycogen, cellulose, chitin).
Lipids
- Lipids are hydrophobic molecules, mainly carbon and hydrogen, used for energy storage, insulation, hormones, and cell membranes.
- Fatty acids: long hydrocarbon chains with a carboxylic acid group.
- Unsaturated fatty acids have at least one double bond and are liquid at room temperature.
- Saturated fatty acids have only single bonds and are solid at room temperature.
- Triglycerides: three fatty acids attached to glycerol.
- Phospholipids: glycerol, phosphate group (hydrophilic), and two fatty acids (hydrophobic).
- Sterols: ringed molecules strengthening membranes (e.g., cholesterol, hormones).
Nucleic Acids
- Nucleic acids (DNA and RNA) are long chains of nucleotides.
- DNA: double-stranded, genetic material, uses deoxyribose sugar, bases are adenine, guanine, cytosine, thymine.
- RNA: single-stranded, protein synthesis, uses ribose sugar, uracil replaces thymine.
- Each nucleotide: five-carbon sugar, phosphate group, and nitrogenous base.
Key Terms & Definitions
- Amino acid — protein building block with a unique R group.
- Polypeptide — chain of amino acids forming proteins.
- Monosaccharide — simplest form of carbohydrate (simple sugar).
- Polysaccharide — long chain of monosaccharides.
- Fatty acid — hydrocarbon chain with terminal carboxyl group.
- Triglyceride — lipid of three fatty acids plus glycerol.
- Phospholipid — lipid with glycerol, phosphate, and two fatty acids; key to cell membranes.
- Sterol — complex ringed lipid molecule.
- Nucleotide — subunit of nucleic acids (sugar, phosphate, base).
- Hydrophobic — repels water.
Action Items / Next Steps
- Review the structure and functions of each macromolecule.
- Use flashcards to reinforce key concepts and definitions.
- Prepare for deeper study of DNA and RNA structure and function in upcoming lessons.