All Topics  
Galactose

 

 
   Email Print
   Bookmark   Link
 

 

Galactose
 
 
  Topics Galactose Topic Home

Galactose (Gal) is a type of sugar
Carbohydrate

Carbohydrates or saccharides are the most abundant of the four major classes of biomolecules. They fill numerous roles in living things, such as the storage and transport of energy and structural components ....
 which is less sweet
Sweetness

Sweet is one of the five basic tastes and is almost universally regarded as a pleasure experience. Foods rich in simple carbohydrates such as sugar are those most commonly associated with sweetness, although there are other natural and artificial compounds that are much sweeter, some of which have been used as sugar substitutes for those wi...
 than glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
. It is considered a nutritive sweetener
Sweetener

A sweetener is a food additive which adds the basic taste of sweetness to a food; artificial sweeteners are sugar substitutes....
 because it has food energy
Food energy

Food energy is the amount of energy in food that is available through digestion.Like other forms of energy, food energy is expressed in calories or joules....
.

Galactan
Galactan

Galactan is a polysaccharide consisting of polymerized galactose.See also* agarExternal links...
 is a polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 of the sugar galactose. It is found in hemicellulose
Hemicellulose

A hemicellulose can be any of several heteropolymers present in almost all plant cell walls along with cellulose. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength....
 and can be converted to galactose by hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
. Galactose solubility in water is 68.30 grams per 100 grams of water at 20–25°C.

s found in dairy product
Dairy product

Dairy products are generally defined as foodstuffs produced from milk. They are usually high-energy-yielding food products. A production plant for such processing is called a dairy or a dairy factory....
s, in sugar beet
Sugar beet

Sugar beet , a member of the Chenopodiaceae family, is a plant whose root contains a high concentration of sucrose. It is grown commercially for sugar production....
s and other gum
Natural gum

Natural gums are polysaccharides of natural origin, capable of causing a large viscosity increase in solution, even at small concentrations. In the food industry they are used as thickening agents, gelling agents, Emulsion and Food additive#Categoriess....
s and mucilage
Mucilage

Mucilage is a chemical polarity glycoprotein; an polysaccharide; a polymer produced by most plants and some microorganisms.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as tannins and alkaloids....
s.

It is also synthesized
Biosynthesis

Biosynthesis is a phenomenon wherein chemical compounds are produced from simpler reagents. Biosynthesis, unlike chemosynthesis, takes place within living organisms and is generally catalyst by enzymes....
 by the body, where it forms part of glycolipid
Glycolipid

Glycolipids are carbohydrate-attached lipids. Their role is to provide energy and also serve as genetic marker for Cell recognition.They occur where a carbohydrate chain is associated with phospholipids on the exoplasmic surface of the cell biological membrane....
s and glycoprotein
Glycoprotein

Not to be confused with peptidoglycan or proteoglycan.Glycoproteins are proteins that contain oligosaccharide chains covalently attached to their Peptide side-chains....
s in several tissue
Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
s.

ctose is a monosaccharide
Monosaccharide

Monosaccharides are the most basic unit of carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystal solids....
.






Discussion
Ask a question about 'Galactose'
Start a new discussion about 'Galactose'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Galactose (Gal) is a type of sugar
Carbohydrate

Carbohydrates or saccharides are the most abundant of the four major classes of biomolecules. They fill numerous roles in living things, such as the storage and transport of energy and structural components ....
 which is less sweet
Sweetness

Sweet is one of the five basic tastes and is almost universally regarded as a pleasure experience. Foods rich in simple carbohydrates such as sugar are those most commonly associated with sweetness, although there are other natural and artificial compounds that are much sweeter, some of which have been used as sugar substitutes for those wi...
 than glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
. It is considered a nutritive sweetener
Sweetener

A sweetener is a food additive which adds the basic taste of sweetness to a food; artificial sweeteners are sugar substitutes....
 because it has food energy
Food energy

Food energy is the amount of energy in food that is available through digestion.Like other forms of energy, food energy is expressed in calories or joules....
.

Galactan
Galactan

Galactan is a polysaccharide consisting of polymerized galactose.See also* agarExternal links...
 is a polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 of the sugar galactose. It is found in hemicellulose
Hemicellulose

A hemicellulose can be any of several heteropolymers present in almost all plant cell walls along with cellulose. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength....
 and can be converted to galactose by hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
. Galactose solubility in water is 68.30 grams per 100 grams of water at 20–25°C.

Sources

It is found in dairy product
Dairy product

Dairy products are generally defined as foodstuffs produced from milk. They are usually high-energy-yielding food products. A production plant for such processing is called a dairy or a dairy factory....
s, in sugar beet
Sugar beet

Sugar beet , a member of the Chenopodiaceae family, is a plant whose root contains a high concentration of sucrose. It is grown commercially for sugar production....
s and other gum
Natural gum

Natural gums are polysaccharides of natural origin, capable of causing a large viscosity increase in solution, even at small concentrations. In the food industry they are used as thickening agents, gelling agents, Emulsion and Food additive#Categoriess....
s and mucilage
Mucilage

Mucilage is a chemical polarity glycoprotein; an polysaccharide; a polymer produced by most plants and some microorganisms.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as tannins and alkaloids....
s.

It is also synthesized
Biosynthesis

Biosynthesis is a phenomenon wherein chemical compounds are produced from simpler reagents. Biosynthesis, unlike chemosynthesis, takes place within living organisms and is generally catalyst by enzymes....
 by the body, where it forms part of glycolipid
Glycolipid

Glycolipids are carbohydrate-attached lipids. Their role is to provide energy and also serve as genetic marker for Cell recognition.They occur where a carbohydrate chain is associated with phospholipids on the exoplasmic surface of the cell biological membrane....
s and glycoprotein
Glycoprotein

Not to be confused with peptidoglycan or proteoglycan.Glycoproteins are proteins that contain oligosaccharide chains covalently attached to their Peptide side-chains....
s in several tissue
Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
s.

Relationship to lactose

Galactose is a monosaccharide
Monosaccharide

Monosaccharides are the most basic unit of carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystal solids....
. When combined with glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
, through a dehydration reaction, the result is the disaccharide
Disaccharide

A disaccharide is a sugar composed of two monosaccharides.'Disaccharide' is one of the four chemical groupings of carbohydrates ....
 lactose
Lactose

Lactose is a sugar that is found most notably in milk. Lactose makes up around 2?8% of milk . The name comes from the Latin word for milk, plus the -ose ending used to name sugars....
. The hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 of lactose to glucose and galactose is catalyzed
Catalysis

Catalysis is the process in which the reaction rate of a chemical reaction is either increased or decreased by means of a chemical substance known as a catalyst....
 by the enzyme
Enzyme

Enzymes are biomolecules that catalysis chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called Substrate , and the enzyme converts them into different molecules, the products....
 lactase
Lactase

Lactase , a part of the ?-galactosidase family of enzymes, is a glycoside hydrolase involved in the hydrolysis of the disaccharide lactose into constituent galactose and glucose monomers....
, a ß-galactosidase
Beta-galactosidase

?-galactosidase is a hydrolase enzyme that catalyst the hydrolysis of ?-galactosides into monosaccharides. substrate s of different ?-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins....
. In the human body, glucose is changed into galactose in order to enable the mammary gland
Mammary gland

Mammary glands are the organ s that, in mammals, produce milk for the sustenance of the young. These exocrine glands are enlarged and modified sweat glands and give mammals their name....
s to secrete lactose.

Galactose and glucose are produced by hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 of lactose
Lactose

Lactose is a sugar that is found most notably in milk. Lactose makes up around 2?8% of milk . The name comes from the Latin word for milk, plus the -ose ending used to name sugars....
 by ß-galactosidase
Lactase

Lactase , a part of the ?-galactosidase family of enzymes, is a glycoside hydrolase involved in the hydrolysis of the disaccharide lactose into constituent galactose and glucose monomers....
. This enzyme is produced by the lac operon
Lac operon

The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. It consists of three adjacent structural genes, a promoter, a terminator , and an operator ....
 in Escherichia coli
Escherichia coli

'Escherichia coli' , is a Gram negative bacterium that is commonly found in the lower gastrointestinal tract of warm-blooded animals. Most E....
 (E. coli).

Clinical significance

Two studies have suggested a possible link between galactose in milk and ovarian cancer
Ovarian cancer

Ovarian cancer is a malignant tumor arising from an ovary. Although ovarian cancer is known to occur in many species, the majority of the medical literature and the focus of this article is on ovarian cancer in humans....
. Other studies show no correlation, even in the presence of defective galactose metabolism. More recently, pooled analysis done by the Harvard School of Public Health showed no specific correlation between lactose containing foods and ovarian cancer, and showed statistically insignificant increases in risk for consumption of lactose at =30 g/d. More research is necessary to ascertain possible risks.

There are some ongoing studies which suggest that galactose may have a role in treatment of focal segmental glomerulosclerosis
Focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis is a cause of nephrotic syndrome in children and adolescents, as well as an important cause of kidney failure in adults....
 (a kidney disease resulting in kidney failure and proteinuria). This effect is likely to be a result of binding of galactose to FSGS factor.

Structure and isomerism

The first and last -OH groups point the same way and the second and third -OH groups point the other way. D-Galactose has the same configuration at its penultimate carbon as D-glyceraldehyde
Glyceraldehyde

Glyceraldehyde is a triose monosaccharide with chemical formula Carbon3Hydrogen6Oxygen3. It is the simplest of all common aldoses....
. Galactose is an epimer
Epimer

In chemistry, epimers are diastereomers that differ in configuration of only one stereogenic center. Diastereomers are a class of stereoisomers that are non-superposable, non-mirror images of one another, unlike enantiomers which are non-superposable mirror images of one another....
 of glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
.

Liver galactose metabolism

In the liver, galactose is converted to glucose 6-phosphate in the following reactions:

galacto-uridylphosphogluco- kinase transferasemutase gal --------> gal 1 P ------------------> glc 1 P -----------> glc 6 P ^ \ / v UDP-glc UDP-gal ^ / \___________/ epimerase

Metabolic disorders

There are 3 important disorders involving galactose:

Name Enzyme Description >- | Galactosemia
Galactosemia

Galactosemia is a rare genetics Metabolism Disease which affects an individual's ability to properly metabolize the sugar galactose.Galactosemia is somestimes confused with Lactose-Intolerance, but unlike lactose-intolerance, galactosemia is not something that someone can "grow out of." Once diagnosed, its there for the rest of the persons li...
  		Galactokinase
Galactokinase

Galactokinase is a phosphotransferase that catalyst the phosphorylation of d-galactose to d-galactose-1-phosphate....
 		 Causes cataract
Cataract

A cataract is a clouding that develops in the lens of the eye or in its envelope, varying in degree from slight to complete Opacity and obstructing the passage of light....
s and mental retardation. If a galactose-free diet starts sufficiently early, the cataracts will regress without complications however neurological damage is permanent. |- | UDPgalactose-4-epimerase deficiency 		UDPgalactose-4-epimerase Is extremely rare (only 2 reported cases). It causes nerve deafness. |- | Galactose-1-phosphate uridyl transferase deficiency Galactose-1-phosphate uridyl transferase Is the most problematic, as galactose-free diets do not have considerable long-term effects.