Home > Lactose
 | | | |
Learn more about "Lactose"
|
|
|
Lactose
Lactose (also referred to as ''milk sugar'') is a sugar that is found most notably in milk. Lactose makes up around 2–8% of milk (by weight). The name comes from the Latin word for milk, plus the -ose ending used to name sugars. Its systematic name is β-D-galactopyranosyl-(1↔4)β-D-glucopyranose.
Chemistry
Lactose is a disaccharide that consists of β-D-galactose and β-D-glucose fragments bonded through a β1-4 glycosidic linkage.
Solubility
Lactose has a solubility of 1 in 4.63 measured %w/v. This translates to 0.216 g of lactose dissolving readily in 1 mL of water.
The solubility of lactose in water is 18.9049 g at 25°C, 25.1484 g at 40°C and 37.2149 g at 60°C per 100 g solution. Its solubility in ethanol is 0.0111 g at 40°C and 0.0270 g at 60°C per 100 g solution.Digestion of Lactose (Catabolism)
Infant mammals are fed on milk by their mothers, which is rich in the carbohydrate Lactose. To digest it, an enzyme called lactase (β-D-galactosidase) is secreted by the intestinal Intestinal villus|villi. This enzyme cleaves the lactose molecule into its two subunits; glucose and galactose for absorption.
Since lactose occurs mostly in milk, in most mammals the production of its digestive enzyme, lactase, gradually decreases with maturity, due to lack of constant consumption.
Many people who live in Europe, the Middle East, India, and parts of East Africa, maintain normal lactase production into adulthood. In many of these areas, milk from mammals such as cattle, goats, and sheep is used as a large source of food. Hence, it was in these regions that genes for lifelong lactase production first evolution|evolved. The genes of lactose tolerance have evolved independently in various ethnic groups. [
People who are not tolerant may suffer uncomfortable and/or socially unacceptable symptoms of too much lactose consumption. In this case, lactose is not broken down and provides food for gas producing gut flora. This leads to bloating, and flatulence and perhaps GI upset.
]
Production of Lactose (Anabolism)
Lactose is produced (an anabolic pathway) in the mammary glands during lactation. Lactose is formed when galactose and glucose bind each other. The reaction first starts with two glucose molecules. One of them is converted to an active glucose molecule (UDP-glucose). The UDP-glucose is converted to UDP-galactose by the enzyme UDP-glucose 4-epimerase. The UDP-galactose is then added to the other glucose (by the enzyme galactosyltransferase) to form the disaccharide lactose.
References
Category:Disaccharides
Category:Sweeteners
simple:Lactose
Related Images
Sources: StartLearningNow, Wikipedia | Usage license: GNU FDL
 |
Welcome to Start Learning Now.
Explore to your heart's content, and we hope you enjoy reading the material we
have assembled for you here! |
 |
| | | | |
Related News
|
|
Further Resources
|
|
Related Resources
search
|
|
