Glucose is the most important source of energy for your body, and there are many mechanisms in place to maintain an appropriate blood glucose level. This ensures that there is sufficient energy available for your body to move, grow and perform all the functions that are required on a daily basis. The stored energy in glucose is released in the cells of the body using a number of specific enzymes in a process called glucose oxidation.
What is Glucose?
Glucose is a simple sugar, or monosaccharide, containing six carbon molecules. This differentiates it from other well-known types of sugar such as fructose, which has five carbons, and sucrose, the kind of sugar you put in your coffee, which is a double sugar composed of one molecule of fructose and one of glucose. Glucose can be formed through the breakdown of complex sugars, or carbohydrates, which should make up around two-thirds of our dietary intake for energy.
Uses of Glucose in the Body
Glucose is your body's primary source of energy. The energy is released in your cells through a process of glucose oxidation, also known as respiration, which is a long pathway of complex metabolic reactions requiring oxygen. Ultimately, this results in the release of energy in the form of ATP, which your body can use to perform all sorts of useful tasks such as the growth and repair of cells.
Oxidation
Glucose is absorbed from your gut after eating, and travels via the blood to the cells that require energy. Oxygen is inhaled through your lungs and also travels in the red blood cells to these same energy-deficient cells where glucose oxidation commences. Here, both molecules are transported into the cell and a series of enzymes start to break down the sugar molecule, using the oxygen, in a step-wise process. The oxygen is then finally incorporated into the end products, water and carbon dioxide. The process releases a little energy at each stage and allows your body to harness the energy efficiently, rather than burning, or oxidizing, it in one go.
Energy Yield from Oxidation
Glucose oxidation in the cells of your body allows you to gain 266 kilocalories of energy per mole, which is approximately 180 grams, of glucose. If you were to oxidize, or burn, the same amount of glucose with a flame in a laboratory, you would get 686 kilocalories of energy, which is lost to the environment as useless heat. This means that the process of glucose oxidation in the body is almost 40 percent efficient at turning potential energy into useful energy for the cells.
Alternative Energy Sources
If there is insufficient glucose available in the blood to provide energy for the cells, the body will acquire additional sugars by breaking down glucose stores in the liver or by signalling hunger to get you to eat. If no more carbohydrates or simple sugars are provided for glucose oxidation, the body will start breaking down fats and proteins and turn them into smaller molecules, which can finally enter the same pathway as glucose to provide the much-needed energy.
