- Glucose has an important function in biology because cells use it as a source of energy and it is an important metabolic intermediate in many chemical reactions. Chlorophyll, the green pigment in plants, uses carbon dioxide and sunlight as an energy source to produce glucose, the main end product of photosynthesis. In animals, it is synthesized in the liver and kidneys from intermediate compounds such as pyruvate and glycerol in the gluconeogenesis metabolic pathway. Some primitive deep-sea bacteria produce it through a chemosynthesis process.
- Although glucose is a "simple sugar," it is a complex molecule. As a linear chain of six carbons, it can close into a six-carbon ring in solution. The molecular formula is C6H12O6, which can also be expressed as C6(H2O). Its molar mass is 180.16 g/mol and the density is 1.54 g/cm3. The solubility in water is 91 g/100 ml at 25 degrees Celsius.
- Isomers are chemical compounds that contain the same numbers of atoms of the same elements but differ in structural arrangement and properties. The ring form of glucose can form two isomers from this conformation. They are a-glucose and b-glucose. Their melting points differ by four Celsius degrees: a-glucose melts at 146 degrees Celsius and b-glucose melts at 150 degrees Celsius. If both isomers are placed together in a water solution in equal amounts, they will interconvert until a stable ratio a:b of 36:64 is reached. This process is called mutarotation.
- The glucose molecule can take on more structural differences. All the structures may be classified in two families of mirror images or stereoisomers. The only set of stereoisomers that occur naturally are called D-glucose, the right handed form which is often called dextrose. Solutions of dextrose rotate polarized light to the right. The "D" in D-glucose refers to the dextrorotary, from the Latin word, "dexter" or right.
- Glucose is used as a source of energy in most organisms, from the most primitive procaryotic bacteria to humans. It may be used by aerobic respiration, anaerobic respiration or fermentation. The major source of energy in the human body is carbohydrates. Their breakdown yields both monosaccharides and disaccharides. Glucose is oxidized through glycolysis and in the citric acid cycle reactions, it forms CO2, water and energy molecules such as ATP (adenosine tri-phosphate). It is the primary source of energy for the brain. When its availability influences the psychological processes or glucose is low, those mental processes are impaired.
- The function of the pancreas is to make enough insulin to keep the glucose supply in balance. When the insulin titers in the blood are sufficient, the liver will temporarily shut down its glucose production as the blood carries its glucose to the body cells. If glucose is in excess, it is converted to glycogen, which is stored in the liver until needed. In diabetes, the balance is disrupted when insufficient insulin is produced. Then the rise of blood glucose levels is unhealthy. If diabetes is not treated, the high glucose levels are indicated by excessive urination, dehydration, intense thirst and fatigue. The long-term results can affect the eyes, kidneys, nerves and blood vessels.
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