What is the primary role of carbohydrates in living organisms?

Carbohydrates primarily serve to provide energy for living organisms. They are organic compounds made up of carbon, hydrogen, and oxygen, and are often the body's main source of energy. When consumed, carbohydrates are broken down into glucose, which is then used as fuel for cellular processes. This energy can be used immediately for metabolic activities or stored as glycogen in animals (and starch in plants) for later use.

In addition to energy provision, carbohydrates play a role in cell structure and signaling, but their most significant and primary function in the context of everyday metabolism is energy supply. This is why the correct answer highlights the role of carbohydrates as a source of energy.