Which carbohydrate is considered the most important biological molecule for providing chemical energy in cells?

• A. Cellulose
• B. Starch
• C. Glucose
• D. Glycogen

Answer: (C)

Verified step by step guidance

1. Understand the role of carbohydrates in biological systems: Carbohydrates are organic molecules that serve as a primary source of energy for cells. They can be simple sugars (monosaccharides) or complex carbohydrates (polysaccharides).
2. Identify the function of each carbohydrate listed: Cellulose is a structural polysaccharide found in plant cell walls, not primarily used for energy. Starch is a storage polysaccharide in plants, broken down into glucose for energy. Glycogen is a storage polysaccharide in animals, also broken down into glucose. Glucose is a monosaccharide directly used in cellular respiration to produce energy.
3. Recall the process of cellular respiration: Glucose is the key molecule used in cellular respiration, where it is oxidized to produce ATP (adenosine triphosphate), the energy currency of the cell. The chemical equation for cellular respiration is: $C_6{H}_{12}{O}_6+6O_2\to 6{\mathrm{CO}}_2+6H_{2}O+\mathrm{ATP}$
4. Compare the listed carbohydrates: While starch and glycogen are storage forms of glucose, they must first be broken down into glucose before being used for energy. Glucose itself is the immediate molecule utilized in cellular respiration, making it the most important biological molecule for providing chemical energy.
5. Conclude that glucose is the correct answer: Based on its direct role in cellular respiration and energy production, glucose is the most important carbohydrate for providing chemical energy in cells.