Which substance is primarily stored by the liver and muscles?

The substance primarily stored by the liver and muscles is glycogen. Glycogen is a polysaccharide that serves as a form of energy storage in animals and fungi. In humans, when glucose is in excess, the body converts it into glycogen through a process called glycogenesis.

The liver can store glycogen and releases glucose into the bloodstream when needed to maintain blood sugar levels, especially between meals or during physical activity. Muscles also store glycogen, but primarily for their own use during exercise, particularly during intense or prolonged physical activity.

Glycogen provides a quick source of energy because it can be rapidly broken down into glucose when the body needs immediate energy. This rapid availability is crucial for maintaining energy levels during high-intensity activities and is a key reason why it is the primary storage form of energy in the liver and muscles.