Overview
This lecture covers the foundations of biochemistry in AP Biology, focusing on chemical bonds, properties of water, carbon's versatility, macromolecules, and protein structure.
Chemical Bonds and Properties of Water
- Ionic bonds form when an atom donates electrons to another atom.
- Covalent bonds involve atoms sharing electrons.
- Polarity and electronegativity result in molecules like water being polar.
- Hydrogen bonds form between the positive and negative regions of polar molecules, especially in water.
- Water's emergent properties include cohesion, adhesion, surface tension, high specific heat, evaporative cooling, ice floating, and being a universal solvent.
- Acids increase H+ concentration in solutions; bases decrease H+ concentration.
- Buffers resist significant changes in H+ concentration, maintaining pH stability.
Carbon and Organic Molecules
- Organic compounds are molecules containing carbon.
- Carbon forms single, double, or triple bonds and can create various molecular shapes (chains, branches, rings).
- Hydrocarbons consist only of carbon and hydrogen.
- Functional groups (hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, methyl) give organic molecules specific properties.
- ATP, the energy currency of the cell, contains three phosphate groups.
- Diamond is pure carbon arranged in a strong crystal lattice.
Macromolecules: Synthesis, Structure & Function
- Dehydration reactions build polymers; hydrolysis breaks them down.
- Four types of macromolecules: carbohydrates, proteins, nucleic acids, and lipids.
- Carbohydrates: monosaccharides (glucose, fructose, galactose), disaccharides (sucrose, maltose, lactose), polysaccharides (starch, glycogen—branched; cellulose—linear; chitin; peptidoglycan).
- Glycosidic linkages connect sugar molecules in carbohydrates.
- Proteins: built from 20 unique amino acids; serve as enzymes, structural units, hormones, receptors, transporters, and antibodies.
- Nucleic acids: DNA (A, T, C, G; double helix) and RNA (A, U, C, G; single strand) store and transfer genetic information.
- Lipids: triacylglycerols (energy storage), phospholipids (cell membranes), steroids (4 fused rings), cholesterol (membrane fluidity).
Protein Structure
- Primary structure: sequence of amino acids.
- Secondary structure: hydrogen bonds form alpha-helix or beta-sheets.
- Tertiary structure: 3D folding from interactions between side chains (disulfide bridges, hydrogen bonds, van der Waals forces).
- Quaternary structure: assembly of multiple polypeptide chains (e.g., hemoglobin).
Key Terms & Definitions
- Ionic bond — electron transfer between atoms.
- Covalent bond — electron sharing between atoms.
- Polarity — uneven distribution of electrical charge in a molecule.
- Hydrogen bond — weak bond between partially charged regions of molecules.
- Buffer — substance that resists pH changes.
- Hydrocarbon — molecule composed of only hydrogen and carbon.
- Glycosidic linkage — bond connecting sugar molecules.
- Amino acid — building block of proteins.
- Polypeptide — chain of amino acids.
- Triacylglycerol — lipid with one glycerol and three fatty acids.
- Phospholipid — lipid with glycerol, phosphate head, and two fatty acids.
Action Items / Next Steps
- Study functional groups and their properties using the provided cheatsheet.
- Review macromolecule structures and functions with the study guide link.
- Practice with the AP Biology Practice Portal for exam preparation.