AP Biology Study Guides

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Unit 1: Chemistry of Life

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Unit 1. Chemistry of Life
- Life depends on the chemical properties of water: polarity, hydrogen bonding, cohesion, adhesion, high specific heat, high heat of vaporization, and ice being less dense than liquid water.
- Hydrogen bonds are weak individually but powerful collectively; they stabilize water properties, DNA base pairing, and protein structure.
- Carbon is central because it can form four covalent bonds, allowing diverse organic molecules and complex carbon skeletons.
- Functional groups determine many molecule properties: hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, and methyl.
- Biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids; structure determines function.
- Carbohydrates include monosaccharides, disaccharides, and polysaccharides. Starch and glycogen are energy storage; cellulose and chitin are structural.
- Lipids are hydrophobic and include triglycerides, phospholipids, and steroids. Phospholipids are amphipathic and form membranes.
- Proteins are polymers of amino acids linked by peptide bonds. Their function depends on shape, which depends on primary, secondary, tertiary, and quaternary structure.
- Denaturation changes protein shape and function, often due to pH, salinity, or temperature changes.
- Nucleic acids store and transmit genetic information. DNA and RNA are built from nucleotides containing a sugar, phosphate group, and nitrogenous base.
- Dehydration synthesis builds polymers by removing water; hydrolysis breaks polymers by adding water.
- Structure-function relationships are constant exam territory: saturated vs unsaturated fats, alpha vs beta glucose linkages, amino acid side chains, and nucleotide sequence effects.

Don't Mix These Up

High-probability confusions for the selected unit.

Hydrogen bond vs covalent bond: hydrogen bonds are weaker intermolecular or intramolecular attractions; covalent bonds share electrons.
Monomer vs polymer: monomers are subunits; polymers are chains of subunits.
Dehydration synthesis vs hydrolysis: dehydration builds; hydrolysis breaks.
Saturated vs unsaturated fat: saturated has no double bonds and is straighter; unsaturated has one or more double bonds and kinked chains.
Starch/glycogen vs cellulose: starch and glycogen use alpha glucose for storage; cellulose uses beta glucose for structure.
DNA vs RNA: DNA usually has deoxyribose and thymine; RNA usually has ribose and uracil.

Must-Know Terms

Quick vocabulary scan before you jump into questions.

polarityhydrogen bondcohesionadhesionspecific heatheat of vaporizationfunctional groupmonomerpolymerdehydration synthesishydrolysiscarbohydratelipidproteinnucleic acidamino acidpeptide bonddenaturationphospholipidtriglyceridesaturated fatunsaturated fatnucleotide