Advanced Placement (AP) Biology Practice Exam

Which of the following describes macromolecules?

1. They are primarily composed of lipids.

2. They consist of smaller organic molecules forming larger ones.

3. They are always hydrophobic in nature.

4. They cannot form through dehydration synthesis.

The correct answer is: They consist of smaller organic molecules forming larger ones.

Macromolecules are large, complex molecules that are crucial for various biological functions and processes. They are formed by the combination of smaller organic molecules, known as monomers, which undergo chemical reactions to create larger structures. This process is typically achieved through dehydration synthesis (or condensation reactions), where water molecules are removed as monomers are joined together. The significance of option B lies in its accuracy in describing the formation of macromolecules, which includes polysaccharides, proteins, nucleic acids, and lipids. The ability for smaller organic molecules to assemble into larger ones is fundamental to the structure and function of biological macromolecules, making this characterization essential for understanding their role in living organisms. Other options do not adequately capture the broader nature of macromolecules. While some macromolecules consist of lipids, it is not true that all macromolecules are primarily composed of them; they also include proteins, nucleic acids, and carbohydrates. Additionally, macromolecules are not always hydrophobic; they can be hydrophilic or amphipathic, meaning they can have both hydrophobic and hydrophilic parts depending on their structure. Lastly, macromolecules are indeed formed through dehydration synthesis, contradicting the statement in the fourth