AP Biology Unit 1 Overview

Overview

This lecture reviews Unit 1 of AP Biology, focusing mainly on the four macromolecules (carbohydrates, proteins, nucleic acids, lipids) and water properties, with practice questions and exam tips.

Unit 1 Resources & Structure

• Daily review questions and FRQ videos are available on AP Bio Penguins Instagram and website.
• Unit 1 covers macromolecules, water properties, and basic practice/Q&A.

Carbohydrates

• Carbohydrates are made of carbon, hydrogen, and oxygen (C:H:O ratio ~1:2:1).
• Monomer is a monosaccharide (e.g., glucose); polymer is a polysaccharide.
• Glycosidic linkages bond monosaccharides.
• Key polysaccharides: cellulose (plant structure), chitin (fungi cell wall/exoskeletons), starch (plant storage), glycogen (animal storage).
• Humans digest alpha linkages (starch), not beta linkages (cellulose).
• Disaccharides: sucrose (glucose + fructose), lactose (glucose + galactose), maltose (glucose + glucose).

Proteins

• Made of C, H, O, N (sometimes S); monomer is an amino acid.
• Amino acid structure: central carbon, amine group, carboxyl group, hydrogen, variable R group.
• Peptide bonds link amino acids between amine and carboxyl groups.
• Levels of structure: primary (amino acid chain), secondary (alpha helix/beta sheet via H bonds), tertiary (R group interactions), quaternary (multiple polypeptides).
• R groups can be hydrophobic, hydrophilic, or charged; folding depends on environment.

Nucleic Acids

• Composed of C, H, O, N, P; monomer is a nucleotide.
• Nucleotide: phosphate group, pentose sugar (deoxyribose or ribose), nitrogenous base.
• Bases: adenine, guanine (purines); cytosine, thymine, uracil (pyrimidines).
• DNA is double-stranded (A-T, C-G); RNA is single-stranded (A-U, C-G).
• Phosphodiester bonds link nucleotides; strands are antiparallel (5' to 3' ends).

Lipids

• Made mostly of C and H, sometimes P (in phospholipids); all non-polar, not true polymers.
• Types: fats (glycerol + 3 fatty acids), phospholipids (glycerol + 2 fatty acids + phosphate), steroids (4 fused rings).
• Saturated fats: all single bonds (solid at room temp); unsaturated: at least one double bond (liquid at room temp).
• Phospholipids form bilayers due to hydrophilic heads, hydrophobic tails.
• Steroids pass through membranes and act as signaling molecules.

Properties of Water

• Polar covalent bonds make water molecules polar.
• Hydrogen bonds form between water molecules, enabling cohesion (water-water) and adhesion (water-other polar substances).
• Capillary action results from cohesion and adhesion.
• High surface tension results from hydrogen bonding.
• Ice is less dense than liquid water due to hydrogen bonds forming open structures.
• High specific heat and evaporative cooling help regulate temperature.
• Water is a universal solvent, dissolving polar and ionic substances.
• pH: negative log of hydrogen ion concentration; as pH increases, H+ decreases.

Practice and Application

• Non-polar R groups fold inward in proteins due to hydrophobic effect; polar R groups are exposed to water.
• Rosalind Franklin’s X-ray diffraction demonstrated DNA's helical structure.
• Glucose is made of C, H, O atoms bonded by covalent bonds.
• DNA backbone breaks occur by breaking covalent bonds between sugar and phosphate (can involve hydrolysis).

Key Terms & Definitions

• Monosaccharide — Simple sugar, carbohydrate monomer (e.g., glucose).
• Polysaccharide — Polymer of monosaccharides (e.g., starch).
• Glycosidic linkage — Bond between carbohydrate monomers.
• Amino acid — Protein monomer, with variable R group.
• Peptide bond — Covalent bond between amino acids.
• Nucleotide — Monomer of nucleic acids: phosphate, sugar, base.
• Phosphodiester bond — Covalent bond linking nucleotides.
• Saturated/Unsaturated fat — Saturated: only single bonds; unsaturated: one or more double bonds.
• Hydrogen bond — Weak attraction between a hydrogen atom and an electronegative atom.
• Cohesion/Adhesion — Cohesion: water-water attraction; adhesion: water-other surfaces.

Action Items / Next Steps

• Review all macromolecule structures and functions.
• Practice identifying bond types in macromolecules.
• Complete water properties multiple choice and FRQ-type questions.
• Check AP Bio Penguins resources for further practice and review.