Kaplan Nursing Entrance Practice Exam

What is the main class of biological molecules that includes sugars and starches?

1. Proteins

2. Carbohydrates

3. Nucleic acids

4. Lipids

The correct answer is: Carbohydrates

The main class of biological molecules that includes sugars and starches is carbohydrates. Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, typically with a hydrogen-to-oxygen ratio of 2:1, similar to water. They are categorized into simple carbohydrates, such as glucose and fructose (the sugars), and complex carbohydrates, like starch and glycogen. Simple carbohydrates are quick sources of energy, while complex carbohydrates provide a more prolonged energy release and play vital roles in bodily functions. Understanding carbohydrates is important in various contexts, including nutrition and metabolism, since they are a primary source of energy for living organisms. They also serve structural roles in certain organisms, such as cellulose in plants. The other classes of biological molecules—proteins, nucleic acids, and lipids—serve different functions. Proteins are essential for a wide range of biological activities, including catalyzing metabolic reactions, providing structural support, and facilitating communication within and between cells. Nucleic acids, like DNA and RNA, are critical for storing and transferring genetic information. Lipids, including fats and oils, are primarily used for storing energy, forming cell membranes, and serving as signaling molecules. Each of these classes has distinct properties and functions separate from those of