Sucrose is a type of disaccharide. Disaccharides are carbohydrates, consist of two molecules attached by a chemical bond. Sucrose consists of equal parts fructose and glucose, which are simple sugars. It is found in many plants. Foods containing fructose include fruits and natural sweeteners. Sucrose is commonly called table sugar, which can be produced from sources such as sugar cane and beets. As a dietary carbohydrate, sucrose is broken down to serve as an energy source. Amounts exceeding caloric needs can be stored by the body.
Sucrose Absorption
As a major dietary carbohydrate, the primary role of sucrose is to provide energy. Because your body cannot absorb sucrose into the blood, an enzyme called sucrase first breaks sucrose down into fructose and glucose, which enter your bloodstream at the level of your small intestine. Fructose rapidly enters a variety of cells for use as energy. On the other hand, glucose requires the presence of insulin, secreted by the pancreas, to enter certain tissues. These include muscle and fat cells.
ATP
Glucose and fructose enter a metabolic pathway known as glycolysis. In this process, your body converts these simple sugars into pyruvate and energy, in the form of ATP, or adenosine triphosphate. ATP is the energy currency of your cell. Your body uses it to power enzymatic reactions, to synthesize molecules, and to undergo cellular division. Virtually every chemical reaction your body undergoes consumes some amount of ATP, and most of it is derived from sucrose and other sugars.
Krebs Cycle
In the presence of oxygen, glucose and fructose, as pyruvate, are converted to a compound called acetyl-CoA. This compound then enters a chemical pathway known as the Krebs Cycle, or citric acid cycle, a series of reactions that produce carbon dioxide and water. These molecules are expelled from the body on exhalation. Energy production is therefore a process in which the sugar you eat is intimately connected with the oxygen you breathe. Cellular respiration, as the Krebs Cycle is called, accounts for much larger quantities of ATP, and therefore energy, than glycolysis alone.
Sucrose as Stored Fuel
Once you consume sufficient calories to meet your metabolic needs, any additional sucrose you consume, whether in the form of added sweetener or a piece of fresh fruit, is stored as an energy reserve, to be used during fasting or periods of insufficient caloric intake. Stored energy is in two major forms. Glycogen consists of long molecules of glucose. It is made and stored in the liver. Triglycerides are fatty acids attached to a glycerol backbone. These fatty acids can be formed from acetyl-CoA derived from sucrose or other food sources, including protein and fats.
References
- "Biochemistry"; Richard A. Harvey, Ph.D.; 2010
- "Physiology"; Linda S. Costanzo, Ph.D.; 2009
Member Comments