Carbohydrates are best described as which of the following?

• A. They are non-organic energy sources.
• B. They are primarily inorganic molecules.
• C. They do not release energy.
• D. Sugars, starch, and cellulose are examples of carbohydrates and can be broken down to release energy.

Answer: (D)

Carbohydrates are organic molecules built from carbon, hydrogen, and oxygen that serve as a major source of energy for cells. They range from simple sugars to complex polysaccharides like starch and cellulose. When these molecules are broken down by enzymes, the energy stored in their chemical bonds is released and captured as ATP during cellular respiration. Glucose, a simple sugar, is a primary energy fuel; starch provides a stored source of glucose; cellulose is a structural carbohydrate in plants. Humans can’t digest cellulose with our own enzymes, but it’s still a carbohydrate and can be broken down by certain microbes to yield some energy. This combination of examples and energy release makes the description the best fit.