Which macromolecule serves as an energy source for the body?

• A. Carbohydrates
• B. Proteins
• C. Nucleic acids
• D. Lipids

Answer: (A)

Carbohydrates are the primary macromolecule that serves as an energy source for the body. They are made up of sugar molecules, which can be quickly broken down by the body to release glucose. Glucose is vital as it is used by cells throughout the body for energy, particularly in high-demand tissues like the brain and muscles.

This process starts with the digestion of carbohydrates into simple sugars, which are then absorbed into the bloodstream. Once in the bloodstream, glucose can be utilized immediately for energy or stored in the liver and muscles as glycogen for later use. The rapid availability of energy from carbohydrates makes them the body's preferred source, especially during exercise or periods of intense physical activity.

In contrast, while proteins can also be used as an energy source, their primary role is in growth, maintenance, and repair of tissues. Nucleic acids, which include DNA and RNA, primarily function in genetic information storage and transmission, and have no direct role in energy metabolism. Lipids, while they do provide energy as well, serve more as long-term energy storage and are metabolized more slowly compared to carbohydrates. Hence, carbohydrates stand out as the primary energy source due to their quick availability and efficiency in meeting the immediate energy needs of the body.