Unit 1: Chemistry of Life is the foundation of everything else in AP Biology. Understanding how atoms, molecules, and chemical properties influence living systems will set you up for success in later units and on the AP Biology Exam.
In this complete RevisionDojo Unit 1 Review, we’ll cover:
- The core concepts and Learning Objectives from the College Board
- Must-know vocabulary and definitions
- Common AP exam question types
- How this unit connects to later topics like enzymes, DNA, and cellular structure
- Study tips to maximize your points
Unit 1 Overview: The Chemistry of Life
Unit 1 makes up about 8–11% of the AP Biology Exam and forms the biochemical framework for everything in biology.
The unit covers:
- Elements of life – CHONPS (Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur)
- Water properties – cohesion, adhesion, surface tension, high specific heat, solvent abilities
- Macromolecules – proteins, carbohydrates, lipids, nucleic acids
- Structure-function relationships at the molecular level
- pH, buffers, and the chemistry of biological reactions
1. Elements of Life
Key Elements
- Carbon (C): Forms 4 covalent bonds, allowing complex, stable structures
- Hydrogen (H) & Oxygen (O): Found in water and organic molecules
- Nitrogen (N): Essential for amino acids and nucleotides
- Phosphorus (P): Found in ATP and phospholipids
- Sulfur (S): Important in some amino acids (cysteine, methionine)
AP Tip: Questions often focus on how carbon’s bonding properties enable molecular diversity.
2. Properties of Water
Unique Properties
- Cohesion: Water molecules stick to each other (due to hydrogen bonds)
- Adhesion: Water sticks to other substances
- High Specific Heat: Helps regulate temperatures in organisms and environments
- Universal Solvent: Polar nature dissolves many substances
- Ice is Less Dense than Liquid Water: Allows aquatic life to survive in winter
Connection to Life: These properties influence nutrient transport, temperature stability, and biochemical reactions.
3. Macromolecules
Carbohydrates
- Monomers: monosaccharides (glucose, fructose)
- Polymers: polysaccharides (starch, glycogen, cellulose)
- Functions: energy storage, structural support
Proteins
- Monomers: amino acids
- Structure levels: primary → secondary → tertiary → quaternary
- Functions: enzymes, structural proteins, signaling molecules
Lipids
- Fats, phospholipids, steroids
- Hydrophobic due to nonpolar bonds
- Function: energy storage, membrane structure, signaling
Nucleic Acids
- Monomers: nucleotides (A, T/U, G, C)
- DNA & RNA store and transmit genetic information
4. Structure-Function Relationships
The shape of biological molecules determines their function. Even small changes (mutations, pH shifts) can cause loss of function—critical for understanding enzyme activity and protein folding.
5. pH and Buffers
- pH scale: 0–14; biological systems typically ~7
- Buffers: maintain pH by binding/releasing H+ ions
- Example: blood buffer system using carbonic acid
Common AP Biology Exam Questions for Unit 1
Multiple Choice Examples:
- Identify which property of water allows plants to transport water from roots to leaves.
- Predict the effect of removing nitrogen from an ecosystem on protein synthesis.
FRQ Examples:
- Explain how the structure of a macromolecule impacts its function.
- Design an experiment to test how temperature affects enzyme activity in a protein.
Unit 1 Connections to Other Units
- Unit 2 (Cell Structure): Phospholipids form the basis of membranes
- Unit 3 (Cellular Energetics): ATP (nucleic acid derivative) powers reactions
- Unit 6 (Gene Expression): DNA structure and replication depend on chemical properties
Study Tips for Unit 1
- Draw Molecular Structures: Practice drawing and labeling monomers and polymers.
- Make Comparison Charts: For macromolecules—include monomer, bond type, function.
- Practice with Data Sets: Graph enzyme activity under different pH/temperature conditions.
- Use Mnemonics: CHONPS for elements of life; “Cats Play Like Naughty Pandas” for macromolecules order.
Frequently Asked Questions
1. How many questions on the AP Bio exam are from Unit 1?
Roughly 8–11% of the exam.
2. Are chemical formulas required knowledge?
You should recognize them for macromolecules, but not memorize every formula.
3. What’s the hardest part of Unit 1?
Understanding how structure relates to function across different molecules.
4. How can I prepare for Unit 1 FRQs?
Practice explaining why molecular properties matter for life processes.
Call to Action
Unit 1 is the foundation of AP Biology—mastering it makes the rest of the course much easier.
👉 Explore RevisionDojo’s full AP Biology review series for detailed breakdowns, practice FRQs, and our AP Bio Score Calculator to track your progress toward a 5.
