Overview
This lecture provides a comprehensive review of AP Biology Unit 1, focusing on macromolecules (carbohydrates, proteins, nucleic acids, lipids), water properties, and related key concepts and practice questions.
Resources & Structure of Unit 1
- AP Bio Penguins offers daily review questions, a review guide, FRQ videos, quizzes, games, and PowerPoints.
- Unit 1 includes macromolecules, water properties, practice questions, and a Q&A.
Carbohydrates
- Composed of carbon, hydrogen, oxygen (C:H:O in 1:2:1 ratio); monomer is monosaccharide.
- Polymers (polysaccharides) include cellulose, chitin, starch, and glycogen.
- Starch (energy storage in plants) has alpha linkages; cellulose (plant structure) has beta linkages—humans can't digest beta linkages.
- Disaccharides formed by glycosidic linkages (e.g., sucrose, lactose, maltose).
Proteins
- Contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur; monomer is amino acid.
- Structure: amino group, hydrogen, carboxyl group, variable R group.
- Levels of structure: primary (amino acid chain), secondary (alpha helix/beta sheet via hydrogen bonds), tertiary (R group interactions), quaternary (multiple polypeptides).
- Peptide bonds link amino acids; directionality from N-terminus to C-terminus.
- R group properties (hydrophobic, hydrophilic, charged) influence protein folding.
Nucleic Acids
- Composed of carbon, hydrogen, oxygen, nitrogen, phosphate; monomer is nucleotide.
- Structure: phosphate group, 5-carbon sugar (ribose/deoxyribose), nitrogenous base (A, T/U, C, G).
- DNA is double-stranded, antiparallel, bases pair A-T (2 bonds), C-G (3 bonds).
- Bonds: phosphodiester linkage (backbone), hydrogen bonds (base pairing).
Lipids
- Made of carbon, hydrogen, oxygen; may include phosphate (in phospholipids).
- Nonpolar, not polymers; includes fats, phospholipids, steroids.
- Fats: glycerol + fatty acids (saturated—solid, unsaturated—liquid).
- Phospholipids: form bilayer with hydrophilic heads, hydrophobic tails.
- Steroids: 4 fused rings; function as signaling molecules (e.g., hormones).
Properties of Water
- Polar covalent bonds create partial charges; hydrogen bonding between molecules.
- Cohesion (water-water attraction) and adhesion (water-other polar surfaces) lead to capillary action.
- Universal solvent for polar/charged substances.
- High surface tension due to hydrogen bonding.
- Less dense as a solid (ice floats) due to hydrogen bonding structure.
- High specific heat provides thermal stability.
pH Concepts
- pH = –log[H+]; as pH increases, H+ concentration decreases (inverse relationship).
- Important for understanding processes like cellular respiration and membrane spaces.
Practice Questions & Application
- Protein folding: nonpolar R groups are buried inside due to hydrophobic interactions.
- Rosalind Franklin’s x-ray photo showed DNA has a double helix.
- Glucose composition: carbon, hydrogen, oxygen; held by covalent bonds.
- DNA breaks occur at the phosphodiester bond between sugar and phosphate (broken by hydrolysis).
Key Terms & Definitions
- Monosaccharide — single sugar molecule, carbohydrate monomer.
- Polysaccharide — polymer of sugars.
- Glycosidic linkage — bond joining sugar monomers.
- Amino acid — protein monomer with central carbon, amino, carboxyl, R group.
- Peptide bond — covalent bond between amino acids.
- Nucleotide — nucleic acid monomer: phosphate, sugar, nitrogenous base.
- Phosphodiester linkage — covalent bond in nucleic acid backbone.
- Hydrogen bond — weak attraction between partial charges, key in water and macromolecules.
- Hydrophobic/Hydrophilic — repelled by or attracted to water, respectively.
- Saturated/Unsaturated fat — no double bonds/all single bonds vs. at least one double bond.
Action Items / Next Steps
- Review macromolecule structures, monomers, bonds, and functions.
- Practice identifying water’s properties and interpreting pH changes.
- Complete daily review questions and practice FRQs available through AP Bio Penguins.