Glucose is colloquially known as dextrose and belongs to the carbohydrates. Glucose represents the most important source of energy for the body. Diseases of the liver, endocrine system, or kidneys can lead to glucose metabolism disorders.
What is glucose?
Glucose is a so-called monosaccharide, a simple sugar. It is a component of normal household sugar and also a building block of longer-chain carbohydrates such as starch or glycogen. Glucose is also present in most fruits in addition to fructose. Glucose belongs to the aldose family. These are sugar molecules that have an aldehyde function. There are two different forms of glucose, D-glucose and L-glucose. But only D-glucose is of natural origin. It is also known as glucose. In the past, it was referred to as dextrose. In the crystalline state, glucose appears as a white water-soluble powder with a sweet taste. Chemically, glucose is a polyalcohol with a molecular skeleton of six carbon atoms. The exact chemical formula of glucose is C6H12O6.
Function, effect and tasks
Glucose is the most important energy supplier of the human body. On average, an adult human at rest requires about 200 g of glucose per day. The majority, about 75 percent, of the glucose ingested is consumed by the brain. The brain and the red blood cells cover their energy requirements solely through glucose. Energy is released in the mitochondria of the body’s cells by glucose breakdown. The process of glucose breakdown is also called glycolysis. Glycolysis produces, among other things, two ATP molecules. ATP is an abbreviation of adenosine triphosphate. The molecule serves as an energy store within cells and is needed in numerous metabolic processes. A man weighing about 80 kilograms consumes an estimated 40 kilograms of ATP per day. However, glycolysis not only produces these two ATP molecules, but also other products. These are further processed in the so-called citrate cycle. The citrate cycle combines the degradation pathways of carbohydrates, proteins and fat. The end products of the citrate cycle are in turn required for the respiratory chain in the mitochondria, the power plants of the cell. During the process of cellular respiration, another 38 ATP molecules are produced.
Formation, occurrence, properties, and optimal levels
Glucose is found as a building block in dual sugars such as lactose (milk sugar) and cane or beet sugar (sucrose). Glucose is also found in polysaccharides such as raffinose and in polysaccharides such as glycogen, starch or cellulose. Glucose is thus a component of numerous foods. It is produced industrially by enzymatic cleavage of corn or potato starch. This is why glucose used to be called starch sugar. From a biochemical point of view, glucose is mainly produced in plants by photosynthesis from water, sunlight and carbon dioxide. Normally, however, glucose is not present in free form in plants, but is embedded in cell structures. It is only during digestion that these cell structures are broken down and degraded to glucose. Enzymes are needed for this. Carbohydrate digestion in humans begins in the mouth. The enzyme amylase is found in saliva, which breaks down carbohydrates to release glucose. In the small intestine, carbohydrate digestion then continues with enzymes from the pancreas. Because glucose is vital to the human body, there is an emergency mechanism for periods of food deprivation. The liver and kidneys are able to synthesize glucose. This process is also known as gluconeogenesis. From a chemical perspective, gluconeogenesis is a reversal of glycolysis, and gluconeogenesis has a high energy requirement. Six molecules of ATP are consumed in order for one molecule of glucose to be produced. If more glucose is taken in than the body needs, conversion to glycogen occurs. Glycogen synthesis occurs in the liver and muscles. There, the glycogen is stored and then converted again when the need for glucose increases. This process is called glycogenolysis. However, some of the glucose always circulates in the blood. This is the only way the energy supplier can reach the cells. Insulin is needed for its uptake into the cells. The level of glucose in the blood is also known as blood glucose. Normal fasting blood glucose should be below 110 mg/dl or below 6.1 mmol/l.Values of 126 mg/dl or 7.0 mmol/l and above represent manifest diabetes mellitus.
Diseases and disorders
Diabetes mellitus is a metabolic disease associated with elevated blood glucose levels. A distinction is made between type 1 diabetes mellitus and type 2 diabetes mellitus. In type 1, there is an absolute lack of insulin due to a disorder of the pancreas. In type 2, on the other hand, sufficient insulin is usually still produced, but due to insulin resistance, the glucose is no longer absorbed properly by the body’s cells. Diabetes mellitus is characterized by a strong urge to urinate, increased thirst, dry skin and susceptibility to infections. The long-term consequences of elevated blood glucose levels are feared. An elevated blood glucose level is also known as hyperglycemia. Damage to the small and large arteries as well as the nerves leads to eye and kidney diseases. Hypoglycemia can also occur as part of diabetes, but also due to other diseases or metabolic processes. Hypoglycemia is defined as a blood glucose level that is too low. If the blood glucose level is below 50 mg/dl, symptoms such as sweating, clouding of consciousness or coma occur. Hypoglycemia often occurs after an overdose of insulin or oral antidiabetic drugs.
