Overview
This lecture covers foundational topics in AP Biology Unit 1, including water chemistry, elements of life, biomolecule families (carbohydrates, lipids, proteins, nucleic acids), and key concepts like hydrogen bonding and macromolecular structure.
Properties of Water & Hydrogen Bonding
- Water is a polar molecule with partial negative and positive regions.
- Hydrogen bonds are weak interactions between molecules, not within molecules.
- Hydrogen bonds are crucial for the structure of DNA, RNA, and proteins.
- Cohesion is the attraction between water molecules, enabling high surface tension and heat capacity.
- Adhesion is water's attraction to other materials, aiding processes like transpiration in plants.
- Surface tension allows objects to rest on water due to a 'net' of molecules.
Acids, Bases, and pH
- Acidic solutions have more hydrogen ions (H⁺) and a pH below 7.
- Basic solutions have more hydroxide ions (OH⁻) and a pH above 7.
- pH concepts may appear within broader questions on the AP exam.
Elements of Life
- Key elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur (CHNOPS).
- Carbon is central to organic molecules; hydrogen is key in energy exchange and gradients.
Monomers, Polymers, and Functional Groups
- Monomers are building blocks; polymers are chains of monomers.
- Dehydration synthesis builds polymers by removing water.
- Hydrolysis breaks polymers by adding water.
- Functional groups (phosphate, methyl, hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, acetyl) influence molecular behavior.
Carbohydrates
- Carbohydrates: monosaccharides (simple sugars), disaccharides (two sugars), polysaccharides (energy storage or structure).
- Humans digest starch but not cellulose; some animals rely on symbiotic organisms to break down cellulose.
- Lactose intolerance results from lack of lactase enzyme in adulthood.
Lipids
- Lipids are nonpolar and hydrophobic; not built from repeating monomers.
- Functions: energy storage (fats/oils), waterproofing (waxes), membrane structure (phospholipids), signaling (steroids).
- Phospholipids have hydrophilic heads and hydrophobic tails, forming cell membranes.
Proteins
- Protein monomer: amino acid (central carbon, amino group, carboxyl group, variable R group).
- All life uses 20 amino acids.
- Four levels of structure: primary (sequence), secondary (alpha helix, beta sheet), tertiary (R group interactions), quaternary (multiple polypeptides).
- Hemoglobin is a quaternary protein; sickle cell disease results from a single amino acid change affecting protein shape and function.
Nucleic Acids (DNA & RNA)
- Function as molecules of heredity and information transfer.
- Monomer: nucleotide (five-carbon sugar, phosphate group, nitrogenous base).
- DNA uses deoxyribose with bases A, T, C, G; RNA uses ribose with A, U, C, G.
- DNA structure: two antiparallel strands held together by hydrogen bonds (A-T, C-G).
- Nucleic acids are synthesized in the 5’ to 3’ direction.
Key Terms & Definitions
- Hydrogen Bond — weak attraction between partially charged regions of molecules.
- Cohesion — attraction between like molecules (e.g., water-water).
- Adhesion — attraction between different substances (e.g., water-cellulose).
- Monomer — small unit that can join to form polymers.
- Polymer — large molecule composed of repeating monomers.
- Dehydration Synthesis — reaction that builds polymers by removing water.
- Hydrolysis — reaction that breaks polymers by adding water.
- Phospholipid — lipid with hydrophilic head, hydrophobic tail, forms membranes.
- Amino Acid — protein monomer with amino, carboxyl, and R group.
- Nucleotide — monomer of nucleic acids (sugar, phosphate, base).
- Primary, Secondary, Tertiary, Quaternary Structure — levels of protein organization.
Action Items / Next Steps
- Review the Unit 1 checklist at apbiosuccess.com/checklist.
- Complete readings and practice questions on learn-biology.com.
- Memorize the four biomolecule types and their monomers.
- Practice drawing/listing functional groups and their roles.
- Review key diagrams: water polarity, dehydration synthesis, DNA/RNA structure.