AP Biology Unit 1 – Chemistry of Life
Unit 1 of AP Biology focuses on the chemistry of life, covering macromolecules, water properties, enzymes, and basic biochemistry. To help you prepare for the AP Bio exam, we’ve compiled essential questions with detailed answers and explanations.
This guide will strengthen your understanding of biological molecules, hydrogen bonding, and enzyme function—all critical topics for the AP test.
1. What Are the Properties of Water That Support Life?
Question:
Why is water essential for life, and what properties make it biologically important?
Answer:
Water’s unique properties are due to hydrogen bonding and its polar nature, enabling life to exist.
Key Properties of Water:
✅ Cohesion & Adhesion: Water molecules stick to each other (cohesion) and other surfaces (adhesion), enabling capillary action in plants.
✅ High Specific Heat: Water resists temperature changes, helping organisms maintain homeostasis.
✅ Universal Solvent: Water dissolves polar and ionic substances, facilitating biochemical reactions.
✅ Density of Ice: Ice floats because it’s less dense than liquid water, insulating aquatic life in winter.
💡 AP Exam Tip: Cohesion and adhesion contribute to transpiration in plants, moving water from roots to leaves!
2. What Are the Four Major Macromolecules?
Question:
What are the four biological macromolecules, and what are their functions?
Answer:
Living organisms are made of four macromolecules:
| Macromolecule | Monomer | Function | Example |
|---|---|---|---|
| Carbohydrates | Monosaccharides | Quick energy & structure | Glucose, Starch |
| Lipids | Fatty Acids & Glycerol | Long-term energy, membranes | Phospholipids, Steroids |
| Proteins | Amino Acids | Enzymes, structure, transport | Hemoglobin, Keratin |
| Nucleic Acids | Nucleotides | Genetic information storage | DNA, RNA |
💡 AP Exam Tip: Proteins fold into complex structures (primary, secondary, tertiary, quaternary) which determine function!
3. How Do Enzymes Work?
Question:
What are enzymes, and how do they speed up biological reactions?
Answer:
Enzymes are biological catalysts that lower the activation energy of chemical reactions.
Key Enzyme Concepts:
✅ Substrate & Active Site: The substrate binds to the enzyme’s active site, forming an enzyme-substrate complex.
✅ Lock-and-Key vs. Induced Fit Model: The induced fit model explains how enzymes adjust to fit substrates.
✅ Factors Affecting Enzyme Activity:
- Temperature & pH: Extreme conditions denature enzymes, altering function.
- Substrate Concentration: Higher substrate levels increase reaction rates until saturation.
💡 AP Exam Tip: Competitive inhibitors bind to the active site, while non-competitive inhibitors bind elsewhere, changing enzyme shape!
4. What Is the Role of Carbon in Biological Molecules?
Question:
Why is carbon the backbone of all organic molecules?
Answer:
Carbon is essential for life because of its tetravalency, allowing it to form four covalent bonds with other atoms. This enables complex molecules like carbohydrates, proteins, lipids, and nucleic acids to form.
Key Carbon Properties:
- Forms single, double, and triple bonds
- Creates large, stable, yet diverse molecules
- Enables functional groups (hydroxyl, carboxyl, amino, phosphate) to attach and provide chemical diversity
💡 AP Exam Tip: Carbon’s versatility allows for the formation of hydrocarbons, isomers, and functional groups in biomolecules!
5. What Is the Importance of pH and Buffers in Biological Systems?
Question:
How do buffers help maintain pH homeostasis in living organisms?
Answer:
pH measures hydrogen ion concentration (H⁺), and buffers stabilize pH by absorbing or releasing H⁺ ions.
Key pH & Buffer Concepts:
✅ Acids: Release H⁺ (e.g., stomach acid, pH ~2)
✅ Bases: Absorb H⁺ (e.g., blood, pH ~7.4)
✅ Buffer Systems: Prevent drastic pH changes (e.g., bicarbonate buffer in blood)
💡 AP Exam Tip: Enzymes function best at optimal pH levels, and deviations can denature them, altering function!
6. Practice Questions for AP Biology Unit 1
- How does hydrogen bonding contribute to water’s properties?
- What are the structural differences between saturated and unsaturated fatty acids?
- Explain the role of dehydration synthesis and hydrolysis in macromolecule formation.
- How does enzyme structure affect its function, and what happens when an enzyme is denatured?
- Describe how functional groups influence biological molecule properties.
7-What is the difference between passive and active transport?
Answer:
Active Transport : Movement of molecules against their concentration gradient, requiring energy (e.g., sodium-potassium pump).
Passive Transport : Movement of molecules across a membrane without energy input (e.g., diffusion, osmosis).
8- Describe the structure and function of the plasma membrane.
Answer:
The plasma membrane is composed of a phospholipid bilayer with embedded proteins. Its primary functions include:
- Selective Permeability : Allows certain substances to pass while blocking others.
- Cell Signaling : Contains receptors that respond to external signals.
- Compartmentalization : Separates the cell’s internal environment from the external environment.
Explanation:
The phospholipid bilayer forms a barrier due to its hydrophobic tails and hydrophilic heads. Proteins within the membrane facilitate transport (e.g., channel proteins) and communication (e.g., receptor proteins). This structure is vital for maintaining homeostasis.
9- How do enzymes speed up chemical reactions?
Answer: Enzymes speed up chemical reactions by lowering the activation energy required for the reaction to occur. They achieve this by binding to the reactant molecules (substrates) and stabilizing the transition state, making it easier for the reaction to proceed. Enzymes are highly specific, typically catalyzing only one type of reaction.
Explanation: Enzymes are crucial for life because they allow metabolic reactions to occur at rates fast enough to sustain life. Without enzymes, many biochemical reactions would be too slow to support cellular functions. Factors like temperature, pH, and substrate concentration can affect enzyme activity, which is why maintaining homeostasis is critical for organisms.
10-What is the significance of the R-group in amino acids?
Answer: The R-group, or side chain, in amino acids determines the amino acid’s chemical properties and, consequently, its role in protein structure and function. R-groups can be hydrophobic, hydrophilic, acidic, basic, or have other unique properties. The sequence and properties of R-groups in a polypeptide chain dictate how the protein folds into its three-dimensional structure, which is essential for its function.
Explanation: The diversity of R-groups allows for the vast array of proteins found in living organisms. For example, hydrophobic R-groups tend to be found in the interior of proteins, while hydrophilic R-groups are often on the surface, interacting with water. This understanding is crucial for topics like protein folding, enzyme function, and genetic mutations.
Tips for Mastering AP Biology Unit 1
Understand the Big Picture: Focus on how chemical principles apply to biological systems. For example, understand how water’s properties influence cellular processes.- Practice with Real Exam Questions: Use past AP Biology exam questions to test your knowledge and get familiar with the exam format.
- Use Visual Aids: Diagrams and molecular models can help you visualize complex concepts like protein structure and enzyme function.
- Review Regularly: Consistent review is key to retaining information. Use flashcards, summary sheets, or study groups to reinforce your learning.
Conclusion
Mastering AP Biology Unit 1 is essential for success on the AP Biology exam and for building a strong foundation in biology. By understanding the chemistry of life, you’ll be well-prepared to tackle more advanced topics in the course. Use the questions and answers provided in this guide to test your knowledge and deepen your understanding. With consistent practice and a solid study plan, you’ll be on your way to acing the AP Biology exam.
Study AP Biology
Practice Digital SAT
Find us on Facebook