Biological Macromolecules Overview

Overview

This lecture covers the properties and monomer structures of the four classes of biological macromolecules: carbohydrates, proteins, lipids, and nucleic acids.

Biological Macromolecules & Their Monomers

• Biological macromolecules are large molecules built from smaller units called monomers.
• The four classes are carbohydrates, proteins, lipids, and nucleic acids.
• Monomers determine the properties of each macromolecule.

Carbohydrates & Monosaccharides

• Carbohydrate monomers are called monosaccharides (e.g., glucose, fructose, galactose).
• Monosaccharides typically have 3–6 carbons in a ring, ending with the suffix "-ose."
• Glucose is the main biological monosaccharide, essential for cellular respiration.
• Disaccharides (e.g., sucrose, lactose) are two monosaccharides joined by a glycosidic linkage.
• Monosaccharides and disaccharides are simple sugars; polymers of many monosaccharides are called polysaccharides.

Proteins & Amino Acids

• Protein monomers are amino acids; there are 20 types.
• All amino acids have an amino group (NH₂), carboxyl group (COOH), and a variable R group (side chain).
• Amino acids are linked by peptide bonds.
• The properties of proteins are determined by the sequence and nature of R groups in their amino acids.
• R groups can be polar, nonpolar (hydrophobic), electrically charged, or special cases.

Lipids & Fatty Acids

• Lipids are hydrophobic, nonpolar molecules, including fats, phospholipids, and steroids.
• Fatty acids are the monomers in fats (triglycerides) and phospholipids.
• Triglycerides consist of one glycerol and three fatty acids.
• Fatty acids are classified as saturated (single bonds, solid at room temp) or unsaturated (double bonds, bent, liquid at room temp).

Nucleic Acids & Nucleotides

• Nucleic acids (DNA and RNA) are polymers of nucleotides.
• Each nucleotide has a five-carbon sugar, a phosphate group, and a nitrogenous base.
• DNA contains deoxyribose sugar; RNA contains ribose sugar.
• The nitrogenous base (A, T, C, G, or U) distinguishes different nucleotides.

Key Terms & Definitions

• Monomer — small molecule that can join others to form a polymer.
• Polymer — large molecule made from repeating monomers.
• Monosaccharide — simple sugar and monomer of carbohydrates.
• Glycosidic linkage — covalent bond between monosaccharides in carbohydrates.
• Amino acid — monomer of proteins, contains amino and carboxyl groups and an R group.
• Peptide bond — covalent bond linking amino acids in proteins.
• Fatty acid — hydrocarbon chain, monomer of some lipids.
• Triglyceride — lipid made of glycerol and three fatty acids.
• Nucleotide — monomer of nucleic acids, consisting of sugar, phosphate, and nitrogenous base.

Action Items / Next Steps

• Review the structures and properties of monomers for all four macromolecule types.
• Prepare for Topic 1.5: structure and function of macromolecule polymers.