Diholoside
The Diholoside S of the sugars formed by two Ose S (Sugar S simple non-hydrolysable). The rigorous biochemical nomenclature of disaccharides is diholosides (the term of disaccharides fallen in disuse remains valid). The diholosides belong to the category of the Oligoholosides.
The connection formed between the two glucidic monomers is called a osidic Liaison. This connection is hydrolysable by chemical way: concentrated acids hot, and by enzymatic way (see Enzyme): example of the béta-galactosidase for the Hydrolysis of the Lactose. It is important to notice that the formation of a osidic connection blocks (blocks) the activity of the functions which it engages, in particular the reducing activity of the functions Aldéhyde S and the phenomenon of Mutarotation.
Both Ose S engaged by the osidic connection can be only in one cyclized form, the linear forms (very rare because representing less than 0.1% of the oses in aqueous solution) cannot create Covalent bond between them.
Classification
One distinguishes two types of diholosides:
-
reducing diholosides: they are composed of two sub-units, identical or different, whose function pseudoaldéhyde carried by N°1 carbon, (carbon hemiacetalic is thus free), of one of the two oses is committed in a osidic connection with a hydroxyl (OH) of the other ose. The function pseudoaldéhyde of the other ose remains free.
- Maltose (α-D-glcp (1→4) - D-glcp)
- Lactose β-D-galp (1→4) - D-glcp)
- Cellobiose (β-D-glcp (1→4) - D-glcp)
- the diholosides not-reducers: they are composed of two sub-units, identical or different, both bound by their function pseudoaldéhyde.
- Saccharose (α-D-glcp (1→2) - D-fruf)
- Trehalose (α-D-glcp (1→1) - D-glcp)
Simple: Disaccharide
| Random links: | Jean-Baptiste d' Aigremont de Saint-Manvieu | The Street (film) | Kishigami Kojun | Raymond de Bar | Block Up Converter | Banlieue_noire_de_Rosebud,_Minnesota |