Search results
Results From The WOW.Com Content Network
Galactose (/ ɡ ə ˈ l æ k t oʊ s /, galacto-+ -ose, "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. [2] It is an aldohexose and a C-4 epimer of glucose. [3] A galactose molecule linked with a glucose molecule forms a lactose molecule.
l-Glucose is an organic compound with formula C 6 H 12 O 6 or O=CH[CH(OH)] 5 H, specifically one of the aldohexose monosaccharides. As the l-isomer of glucose, it is the enantiomer of the more common d-glucose. l-Glucose does not occur naturally in living organisms, but can be synthesized in the laboratory.
Lactose, or milk sugar, is a disaccharide composed of galactose and glucose and has the molecular formula C 12 H 22 O 11.Lactose makes up around 2–8% of milk (by mass). The name comes from lact (gen. lactis), the Latin word for milk, plus the suffix -ose used to name sugars.
Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose. The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form. Glucose is naturally occurring and is found in its free state in fruits and other parts of plants.
This induces the activity of the operon, which will increase the rate of galactose metabolism. The gal operon is also controlled by CRP-cAMP, similarly to the lac operon. CRP-cAMP binds to the -35 region, promoting transcription from PG1 but inhibiting transcription from PG2. This is accomplished due to the location of the activation sequence.
For instance, galactose and glucose are both aldohexoses, but have different physical structures and chemical properties. The monosaccharide glucose plays a pivotal role in metabolism , where the chemical energy is extracted through glycolysis and the citric acid cycle to provide energy to living organisms.
Of these D-isomers, all except D-altrose occur in living organisms, but only three are common: D-glucose, D-galactose, and D-mannose. The L-isomers are generally absent in living organisms; however, L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens. [6]
The LacY gene is a component of the lac operon that encodes lactose permease, a protein responsible for breaking down lactose into glucose and galactose, alongside transacetylase and beta galactosidase. The absence of lactose permease leads to the inability of lactose to enter the cell for further metabolic processes.