Galactose: Facts, Functions, Formula, and Resources

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What is Galactose and What Are The Functions of Galactose

Galactose is a simple sugar, or monosaccharide (one sugar), which is found in many foods that we eat a lot of on a daily basis. Most commonly, galacose is found in lactose, the disaccharide (two sugars) found in milk and other dairy products. It is also found in complex carbohydrates and in fruits and vegetables such as tomatoes, potatoes, celery, beets, kiwis and cherries. When we consume milk and other dairy products, the mechanisms of our body are such that lactose is not readily absorbed by the small intestine into the blood stream. Therefore, lactase, which is an enzyme found in the brush border of the small intestine, acts as a catalyst to break down the lactose into its more simple components, glucose and galactose, which the body is then able to absorb.

Synonym(s) for Galactose

D-galactose
galactopyranose
galactopyranoside

Where is galactose found?

Glucose and galactose are both classified as hexoses and are very similar in their chemical structure; they both contain six carbon molecules, six oxygen molecules and 12 hydrogen molecules. The difference between the two sugars results from a slight difference in their biochemical structure. Galactose is sometimes known as a brain sugar, since small quantities of the sugar can provide a large amount of energy. Galactose is not as sweet as glucose, which is known as a blood sugar, since it circulates in the blood. Since both glucose and galactose contain calories, they are known as nutritive sweeteners. Galactose has a different structure than many other sugars, making it beneficial in preventing adult-onset diabetes and making it easier for the body to lose and maintain weight.

Besides being found in nature, galactose is also produced by the body and can be found in small traces in the blood and the urine. It is also found in glycolipids, which are located in the brain and other nervous tissues of the body. In mammals, once weaning has been completed and milk intake is decreased, galactose is produced in the body mainly from glucose. It is primarily metabolized in the liver and its metabolism aids in the production of fuel for cellular metabolism. The production of glycoproteins, glycolipids and glycosaminoglycans, found in many tissues of the body, is also aided by galactose in the body. In the body, glucose is also turned into galactose in order to make the mammary glands produce lactase. Galactose can also be produced synthetically, but is not commonly made for home use since its liquid form is not easily dissolved. Some gums and energy drinks are made with galactose and there are dietary supplements available which contain galactose.

One complication that can arise related to galactose is referred to as classic galactosemia. This disorder is a genetic one and arises most commonly from a deficiency of the enzyme Galactose-1-phosphate uridyl transferase (GALT) and can also be caused by impaired function of the liver. Less commonly, galactosemia is caused by a deficiency of galactose kinase or a deficiency of galactose-6-phosphate epimerase. The disorder is not common and is screened for in newborns since it can be life-threatening in infancy. Since there is no known cure, people with galactosemia should treat the disorder with dietary restrictions and should avoid foods which are high in galactose.

Another rare complication related to galactose is known as glucose-galactose malabsorption, which is also a hereditary disorder. In this disorder, the lining of the small intestine is unable to absorb the simple sugars, glucose and galactose, causing severe diarrhea, gas, bloating and dehydration. This disorder is usually diagnosed in the first few days of life but can have a later onset. Like galactosemia, the treatment is to avoid certain foods, in this case ones containing lactose, sucrose and glucose.

Is Galactose a Ketose?

Ketoses are monosaccharides which contain a ketone group, and are known as non-reducing sugars since they are not oxidized by Benedict’s reagent. Aldoses are sugars which contain an aldehyde group. They are known as reducing sugars meaning that they will be oxidized by Benedict’s reagent. Among the hexoses, glucose and galactose are classified as aldoses, not as ketoses.

Galactose Formula

Three common sugars share the same molecular formula: C6H12O6. Because of their six carbon atoms, each is a hexose.

glucose, “blood sugar”, the immediate source of energy for cellular respiration
galactose, a sugar in milk (and yogurt), and
fructose, a sugar found in honey.

Although all three share the same molecular formula (C6H12O6), the arrangement of atoms differs in each case. Substances such as these three, which have identical molecular formulas but different structural formulas, are known as structural isomers.

Glucose, galactose, and fructose are “single” sugars or monosaccharides. Two monosaccharides can be linked together to form a “double” sugar or disaccharide.

Galactose Disorders

1. Obesity
2. Coronary Disease (Coronary Heart Disease)
3. Hypoglycemia (Reactive Hypoglycemia)
4. Gestational Diabetes (Gestational Diabetes Mellitus)
5. Liver Diseases (Liver Disease)

Resources about Galactose

Genetics Home Reference
Elmhurst.edu information about Galactose

Resource by B.Sobey

I am a recent masters graduate from FL. I enjoy the beach, traveling, and writing. I just moved to South Carolina in hopes to find a job as a journalist.

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