The liver and muscles are capable of storing which type of energy source?

The liver and muscles store energy primarily in the form of glycogen, which is a polysaccharide that serves as a readily available energy source. Glycogen is synthesized from glucose through a process called glycogenesis and can be quickly broken down into glucose when the body needs energy, especially during physical activity or between meals.

The liver plays a crucial role in maintaining blood glucose levels by storing glycogen and releasing glucose into the bloodstream as needed. Muscle tissue also stores glycogen, but it primarily utilizes this stored form of carbohydrate for energy during exercise.

While fatty acids can also serve as an energy source and fatty tissues store them, they are not stored in the liver or muscles directly as a major energy reserve. Proteins can be used for energy, but they are not a primary storage form, as their main functions are for building and repairing tissues. Therefore, glycogen is the correct answer, as it specifically refers to how the liver and muscles store energy.