A Level Biology Practice Exam

Which of the following compounds is classified as a non-polar macromolecule?

1. Proteins

2. Nucleic acids

3. Carbohydrates

4. Lipids

The correct answer is: Lipids

Lipids are classified as non-polar macromolecules due to their structural composition, which primarily consists of long hydrocarbon chains or rings. These structures lack significant polar bonding, resulting in an overall non-polar character. This non-polarity is crucial because it influences how lipids interact with other molecules, particularly in biological membranes where they form bilayers due to their hydrophobic nature. In contrast, proteins and nucleic acids have polar areas, as they contain functional groups that engage in hydrogen bonding and interact with water or other polar substances. Carbohydrates also have regions that can form hydrogen bonds due to the presence of hydroxyl groups, making them polar molecules. The non-polar nature of lipids allows them to serve essential roles in biological systems, such as energy storage and cellular membrane formation, where their ability to exclude water is advantageous.