As an expert in the field of human physiology, I can provide you with a detailed explanation regarding the storage of glycogen in the human body.

Glycogen is a polysaccharide that serves as a form of energy storage in animals. It is a branched molecule made up of glucose units linked together by α-1,4 and α-1,6 glycosidic bonds. The role of glycogen is to store glucose, which can be quickly mobilized to provide energy for the body's cells when needed. This is particularly important during periods of fasting, intense physical activity, or when blood glucose levels drop.

The majority of the body's glycogen is stored in two primary locations: the liver and skeletal muscle cells. In the liver, glycogen serves as an important reservoir for maintaining blood glucose levels within a normal range. When blood glucose levels fall, such as during fasting or prolonged exercise, the liver can rapidly break down glycogen into glucose and release it into the bloodstream. This process is regulated by several hormones, including glucagon, which signals the liver to convert glycogen back into glucose.

In skeletal muscle cells, glycogen is stored as a readily available energy source for muscle contraction. Muscle glycogen is particularly important for high-intensity activities and endurance exercise. During exercise, muscle cells can break down glycogen to produce glucose-6-phosphate, which can then be further metabolized to generate ATP, the primary energy currency of the cell. This process is regulated by different enzymes and does not require hormonal signals.

It is worth noting that while the liver and skeletal muscles are the primary sites of glycogen storage, there is evidence to suggest that small amounts of glycogen can also be found in certain glial cells within the brain. However, the exact function and significance of glycogen in the brain are not as well understood as its role in the liver and muscles.

In addition to its role in energy metabolism, glycogen also plays a structural role in cells. For example, in liver cells, glycogen is stored in the cytoplasm and helps to maintain cell volume and shape. In muscle cells, glycogen is stored in close proximity to the myofibrils, which may facilitate rapid access to energy during muscle contraction.

The storage and utilization of glycogen are critical for maintaining energy homeostasis in the body. When glycogen stores are depleted, the body must rely on other sources of energy, such as fats and proteins, which can have implications for overall health and performance.

In summary, glycogen is predominantly stored in the liver and skeletal muscle cells, where it serves as a readily accessible source of glucose for energy production. The liver plays a central role in regulating blood glucose levels by converting glycogen to glucose in response to hormonal signals, particularly glucagon. Muscle cells utilize glycogen to produce ATP during physical activity, ensuring a continuous supply of energy for muscle contraction. Small amounts of glycogen may also be present in brain cells, although its function there is less clear.

read more >>

In addition, small amounts of glycogen are found in certain glial cells in the brain. Sometimes called "animal starch" for its resemblance with starch found in plants, it is stored in liver and muscle cells and can be converted to glucose if needed. In the liver this conversion is regulated by the hormone glucagon.read more >>