Which type of organic molecules serve as the primary sources of energy in biological systems?

Carbohydrates serve as the primary sources of energy in biological systems due to their structure and function. They are composed of carbon, hydrogen, and oxygen and can be easily broken down by organisms to release energy. The simplest form of carbohydrates, known as monosaccharides (e.g., glucose), can be quickly metabolized to produce adenosine triphosphate (ATP), which is the usable energy currency in cells.

Carbohydrates are particularly efficient in energy production because they can be rapidly converted through processes like glycolysis and the Krebs cycle. Additionally, they play a crucial role in various biological processes beyond energy supply, such as cell signaling and structural functions in plant cell walls.

Other organic molecules like proteins and fats can also serve as energy sources, but they typically play differing roles—proteins are primarily needed for growth and repair, while fats provide long-term energy storage and insulation. Nucleic acids, on the other hand, are mainly involved in storing and transferring genetic information and are not directly used for energy. Thus, carbohydrates take precedence as the primary energy sources in biological systems.