Cells inside the human body mostly need glucose for proper functioning. By glucose metabolism, the body technically is able to supply the cells with much-needed fuel. Glucose metabolism is the process which generally converts glucose into energy for cell utilization. This energy mostly is in the form of adenosine triphosphate (ATP). Glycolysis is the term commonly used for the breakdown of glucose into energy for cell use.
The body usually derives glucose from carbohydrates. Many foods which are rich in carbohydrates have high starch and sugar content. They mostly include potatoes, pastas, breads, cereals, rice, and candies. After meals, carbohydrate metabolism technically takes place in the digestive tract where they are converted into glucose and absorbed in the blood. As the glucose level in the blood increases, the pancreas, which is part of the endocrine system, usually is stimulated to release the hormone insulin.
Insulin generally functions to maintain normal levels of glucose in the blood by transporting glucose into the cells. Glucose metabolism usually then takes place to provide fuel to most tissues and muscles inside the body, including the heart muscles as they typically need energy constantly to perform their normal functions. When glucose supply exceeds the needs of the body, they often are stored inside the liver and muscles in the form of glycogen for future use. Excess glucose also often is converted to fatty acids and mostly stored as body fat.
Blood glucose levels sometimes drop after physical activities and in between meals. The cells in the pancreas often respond to the low glucose levels in the blood by producing the hormone glucagon. Glucagon generally functions to increase blood glucose levels in times of low supply.
Through the process of glycogenolysis, glucagon technically converts the glycogen stored in the liver and muscles into glucose. During periods of fasting and starvation, glucagon mostly stimulates the liver to convert non-carbohydrate sources into glucose for cell use to prevent very low levels of glucose in the blood. Examples of these non-carbohydrate sources inside the body are glycerol, amino acids, lactate, and pyruvate.
Any defects in the secretion and function of insulin generally results in the development of diabetes mellitus (DM). In DM, glucose metabolism usually is deranged, often giving rise to elevated levels of glucose in the blood. Symptoms of diabetes include frequent hunger pangs, thirst, and urination. Fasting blood glucose tests typically show elevated glucose levels in the blood even after many hours of fasting.