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AP® Biology Unit 1 Review and Practice Test: Chemistry of Life

Prepare for your AP®  Biology Unit 1 test with our complete Chemistry of Life review. Unit 1 covers water’s properties, macromolecules, and essential biochemistry concepts—the foundation for the entire course. Use our AP Bio Unit 1 review to study with exam-style MCQs, practice tests, and study guide lessons that reflect exactly what’s on the AP exam. Whether you need quick notes, short review videos, or full practice, this resource will strengthen your understanding and help you aim for a top score.

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Boost Your Confidence and Score High with Our AP Biology Unit 1 Review

Dive into AP Biology Unit 1: Chemistry of Life with everything you need to succeed. This AP Bio Unit 1 review covers water’s properties, carbon and macromolecules, and key biochemistry concepts. Practice with AP Biology Unit 1 MCQs and practice tests that mirror the real exam, and reinforce your learning with our step-by-step Unit 1 study guide and engaging video lessons.

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AP Biology Unit 1 Review Videos Anytime

Complex concepts like hydrogen bonding, dehydration synthesis, and macromolecule structure are broken down into clear, visual explanations. Learn faster with short, high-yield videos designed for AP Bio students.

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Our AP Biology Unit 1 study guide covers every topic in the College Board’s CED. Built-in knowledge checks test your understanding of macromolecules, properties of water, and biochemistry fundamentals, so you know exactly what to review.

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Try These AP Biology Unit 1 Practice Test Questions

Get exam-ready with AP Biology Unit 1: Chemistry of Life practice tests. Our AP Bio Unit 1 MCQs mirror the real exam format and include step-by-step explanations with visuals. Use this Unit 1 review to prepare for your next quiz or test, strengthen your understanding of macromolecules and biochemistry, and build the confidence to score high.
Try these sample practice questions with detailed answer explanations:

Question

During RNA synthesis in a cell, a cytosine nucleotide is added to a growing RNA strand ending in a guanine-adenine dinucleotide. Which of the following correctly illustrates the structure and orientation of each nucleotide as the reaction takes place?

A. Nucleic acid synthesis
B. Nucleic acid synthesis
C. Nucleic acid synthesis
D. Nucleic acid synthesis

Explanation

Nucleic acid synthesis

Nucleotides are biological molecules composed of the following:

  • One pentose sugar (ie, ribose in RNA or deoxyribose in DNA)
  • One to three phosphates
  • One of the five nitrogenous bases: adenine, cytosine, guanine, thymine (DNA only), or uracil (RNA only)

The nitrogenous base is attached to carbon 1 of the sugar, all phosphates present are attached to carbon 5 (ie, the 5′ end), and a hydroxyl group (OH) is attached to carbon 3 (ie, the 3′ end).

Nucleotides can combine to form long chains (ie, polymers) known as polynucleotides or nucleic acids (ie, RNA or DNA). In biological systems, this occurs when the 5′ triphosphate (three connected phosphates) on a free nucleotide reacts with the 3′ hydroxyl group of the growing nucleic acid.

In the given RNA synthesis reaction, cytosine (a free nucleotide) is added to a guanine-adenine dinucleotide on the growing nucleic acid. Because cytosine is the free nucleotide in this scenario, it must contain a 5′ triphosphate, which must align with the 3′ hydroxyl group of guanine-adenine for the addition to occur. The diagram shown in Choice C correctly depicts this structure and orientation.

The diagrams shown in Choice A, Choice B, and Choice D show incorrect structures and/or orientations for the nucleotides.

Things to remember:
Nucleotides consist of a pentose sugar linked to a nitrogenous base (ie, adenine, cytosine, guanine, thymine [DNA only], uracil [RNA only]) at carbon 1, one or more phosphates linked to the 5′ end, and a hydroxyl group linked to the 3′ end. Nucleic acids grow when the 5′ triphosphate of a free nucleotide reacts with the 3′ hydroxyl group of the growing nucleic acid chain.

Question

Scientists investigated how water temperature at various depths changed throughout the year in a certain lake. The graph above depicts the relationship between water depth and water temperature recorded during the summer, when environmental temperatures were greater than 4°C, and during the winter, when the environmental temperatures were below the freezing point of water (0°C). Which of the following statements is most consistent with the data shown above?

A. The water temperature increases with increasing water depth during the summer.
B. Water depth and water temperature are directly correlated throughout the year.
C. There is no relationship between water depth and water temperature.
D. Water temperature increases with increasing water depth during the winter.

Explanation

Water molecules consist of one oxygen atom covalently bonded to two hydrogen atoms. The electronegative oxygen pulls harder on the shared electrons than hydrogen, resulting in polar bonds. The increased electron density around the oxygen atom gives it a partial negative charge, and the decreased electron density around each hydrogen atom gives it a partial positive charge.

The attraction between these partial positive and negative charges allows the formation of hydrogen bonds between oxygen and hydrogen atoms of different water molecules.

When environmental temperatures are above approximately 4°C (ie, temperature at which water is most dense), the water temperature in a lake decreases with increasing depth, as depicted in the question graph. This occurs because, at these temperatures, warmer water is less dense than cooler water.

When environmental temperatures reach the freezing point of water, more hydrogen bonds form, causing water molecules to adopt a rigid framework in which water molecules are further from each other than they are in liquid water. As a result, ice is less dense than liquid water. Therefore, when environmental temperatures are at or below the freezing point of water, water temperature in a lake increases with depth (Choice D).

(Choice A) The water temperature decreases with increasing water depth during the summer.

(Choices B and C) There is a relationship between water depth and temperature, but the relationship depends on whether environmental temperatures are above or below freezing.

Things to remember:
Hydrogen bonding between oxygen and hydrogen atoms of adjacent water molecules causes water to become less dense as it freezes.

Question

Solid fatty acid samples were slowly heated in special warming pans until the samples melted. The scientists performing the procedure recorded the melting temperatures, noting that they were dependent on chain length and other characteristics of the lipids. Which plot below best represents the likely study results?

A.
B.
C.
D.

Explanation

Lipids are nonpolar biological molecules with many functions (eg, storing energy, providing structure to cell membranes). Lipids may be saturated or unsaturated based on the types of fatty acids that they possess. These fatty acids are composed of carbon-hydrogen (hydrocarbon) chains. In saturated lipids, fatty acids contain carbon atoms linked only by single bonds, making them essentially straight in structure. In contrast, fatty acids of unsaturated lipids have some double bonds between their carbon atoms that cause structural kinks (ie, bends).

The straighter fatty acid chains of saturated lipids can be packed more tightly, whereas bends in unsaturated lipids prevent them from packing together tightly. Tighter packing increases interactions between fatty acid chains, thereby increasing melting temperature.

The question describes fatty acid melting temperatures measured by a team of scientists and states that these melting temperatures were affected by the chain length of the fatty acids. Since melting temperature is the dependent variable, it should be plotted on the y-axis. Therefore, the plot in Choice D, which shows melting temperature being affected by both chain length and fatty acid saturation, best represents the likely results.

The other graphs either are plotted with incorrect orientation (Choices A and B) or incorrectly depict some fatty acids as polar (Choices B and C).

Things to remember:
Lipids are nonpolar biological molecules. The fatty acids in lipids can be saturated (contain only single bonds between carbon atoms) or unsaturated (contain some double bonds between carbon atoms). Dependent variables are plotted on the y-axis of a line graph.

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Frequently Asked Questions (FAQs)

AP Biology Unit 1 focuses on the chemical principles that govern living organisms. Key topics include the properties of water, the structure and function of macromolecules (carbohydrates, lipids, proteins, and nucleic acids), and the role of enzymes in biological reactions.
A good study plan includes reviewing the key concepts, using flashcards for vocabulary, and taking practice tests. UWorld’s practice questions, including both MCQs and FRQs, are designed to mimic the format and difficulty of the actual AP exam, making them an excellent resource.
Focus on understanding the concepts of polarity, hydrogen bonding, cohesion, adhesion, and high specific heat. Try to connect these properties to their biological significance, such as how they help regulate temperature in living organisms.
UWorld offers a free trial that includes practice questions and detailed explanations for AP Biology Unit 1.
You will likely see questions asking you to identify the structure of the four major macromolecules, explain their functions, and describe the dehydration synthesis and hydrolysis process.
The test will consist of multiple-choice questions (MCQs) and free-response questions (FRQs). The MCQs will test your knowledge of key concepts, while the FRQs will require you to apply your understanding to experimental scenarios and data analysis.
Practice is key. Work through sample FRQs, focus on being concise, and answer prompts directly. This winter, UWorld will offer FRQs with an AI-powered scoring system—giving you excellent practice and detailed explanations to help you understand exactly what graders are looking for.
Unit 1, the Chemistry of Life, typically accounts for 8-11% of the total score on the AP Biology exam. A strong foundation in this unit is crucial for success in the rest of the course.
Our AP Biology prep book features a Unit 1 study guide that covers all key topics, reinforces learning with practice questions, and includes detailed explanations to help you fully master the material.
Yes, UWorld allows you to create customized practice tests that focus solely on Unit 1. This allows you to drill down on the topics you need to review the most, which is an effective way to prepare for your in-class tests and the final AP exam.
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