Overview
This lecture covers the structure, types, and functions of biological macromolecules—carbohydrates, lipids, proteins—and explains how they are built and broken down in the body.
Acid-Base Balance in Blood
- The body maintains blood pH through reactions that remove or absorb hydrogen (H⁺) and hydroxyl ions (OH⁻).
- Buffer systems help maintain homeostasis by neutralizing excess acids or bases.
Organic Molecules & Functional Groups
- Organic molecules always contain carbon and hydrogen.
- Hydrocarbons are molecules made solely of hydrogen and carbon, often used for energy.
- Functional groups like hydroxyl, carbonyl, carboxyl, amino, and phosphate change molecule properties.
Macromolecules: Monomers & Polymers
- Monomers are single building blocks; polymers are long chains of monomers.
- Macromolecules are large polymers found in living things.
- Common macromolecules: carbohydrates (monosaccharide), proteins (amino acid), nucleic acids (nucleotide).
Dehydration & Hydrolysis Reactions
- Dehydration reaction joins monomers by removing water, forming polymers.
- Hydrolysis reaction breaks polymers by adding water, splitting them into monomers.
- Digestion uses hydrolysis to break down food into absorbable monomers.
Carbohydrates
- Monosaccharides (single sugars) have 3-7 carbons; common forms are pentose (5C) and hexose (6C, e.g., glucose).
- Disaccharides are formed by joining two monosaccharides via dehydration (e.g., maltose).
- Polysaccharides (many sugars) include starch (plant storage), glycogen (animal storage), and cellulose (plant structure/dietary fiber).
- Chitin is a structural polysaccharide in exoskeletons.
Lipids
- Lipids store more energy per gram than carbohydrates (8-10 cal/g vs. 4 cal/g).
- Types include fats (triglycerides), oils, phospholipids (cell membranes), and steroids (hormones/cholesterol).
- Fats: solid at room temp (animal), saturated fatty acids (no double bonds), energy storage/insulation.
- Oils: liquid at room temp (plant), unsaturated fatty acids (one or more double bonds), generally healthier.
- Phospholipids have hydrophilic heads and hydrophobic tails; form cell membranes.
- Steroids have ring structures; include cholesterol, estrogen, and testosterone.
Proteins
- Proteins are polymers of amino acids linked by peptide bonds.
- Each amino acid has an amino group, carboxyl group, and unique R group (functional group).
- Functions: structural (keratin, collagen), enzymes, hormones, movement (actin, myosin), transport, immunity (antibodies), membrane channels/pumps.
- Protein structure: primary (amino acid order), secondary (alpha helix/beta sheet), tertiary (3D folding), quaternary (multi-polypeptide complexes).
- Denaturation is the loss of protein shape and function due to pH, heat, or chemicals.
Key Terms & Definitions
- Buffer — system that resists changes in pH by neutralizing acids/bases.
- Monomer — single molecular unit serving as a building block for polymers.
- Polymer — large molecule made of repeating monomers.
- Dehydration reaction — chemical reaction that forms polymers by removing water.
- Hydrolysis — chemical reaction that breaks polymers into monomers by adding water.
- Monosaccharide — simple sugar molecule.
- Polysaccharide — large carbohydrate made of many monosaccharides.
- Saturated fatty acid — fat with only single bonds between carbons.
- Unsaturated fatty acid — fat with one or more double bonds between carbons.
- Peptide bond — bond joining amino acids in a protein.
- Denaturation — loss of protein's shape and function.
Action Items / Next Steps
- Review macromolecule types and their monomers.
- Memorize key functional groups and their effect on molecule properties.
- Prepare for discussion of nucleic acids and enzyme mechanisms in next chapter.