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21 Carboxylic Acid Derivatives -- Part 7
We will look at some naturally occurring disaccharides.
An acetal is a sugar and alcohol mixture.
The alcohol is a disaccharide.
The 1,4' link is the most common linkage.
The oxygen atom on C4 of the second ring is bonded to the anomeric carbon of one sugar.
The anomeric carbon of one unit is linked through a carbon-oxygen bond to another unit.
Its structure is given by (b-d-glucopyranosyl)-b-d-glucopyranose.
A b-d-glucopyranose ring is replaced in its 4-position by an oxygen ring on the left, according to this name.
Cellobiose has aglucose unit in the hemiacetal form and therefore is in equilibrium with its open-chain aldehyde form.
The equilibrium mixture of the two anomers can be seen when sugars are shown with a wavy line.
The first step in making beer is the malting process.
Like cellobiose, maltose has a 1,4' linkage between two units.
The stereochemistry of the glucosidic linkage is different in maltose.
There is a free hemiacetal ring on the right of maltose.
Maltose is a reducing sugar because it is in equilibrium with an open-chain aldehyde.
The structures of the individual mutarotating a and b anomers of maltose can be drawn.
The reduction of Tollens reagent by maltose is shown in the equation.
Lactose is composed of two units.
Lactose is found in the milk of mammals.
A b@galactosidase is needed to hydrolysis of lactose.
Some humans are able to synthesise a b@galactosidase.
Normal infants hydrolyze their mother's milk with the help of this enzyme.
The child stops drinking milk after a while.
In most parts of the world, people don't use milk products after early childhood, and the adult population can't digest Lactose.
Lactose-intolerant infants need to drink soy milk or another formula.
There are two forms of lactose.
The 1,6' linkage is also found in naturally occurring carbohydrates.
The anomeric carbon of one sugar is linked to the oxygen of the other in a 1,6' linkage.
The hydroxy group on C6 is one carbon atom removed from the ring, so this linkage gives a different sort of stereochemical arrangement.
A b@1,6' glucosidic linkage is found in gentiobiose.
The 1,6' linkage is a rare one in disaccharides.
Section 23-13B states that branching in amylopectin occurs at 1,6' linkages.
There is a 1,1' linkage between sugars and their carbon atoms.
The linkage is in the a position with respect to the glucose ring and the b position with respect to the fructose ring.
There are two monosaccharide units in sucrose.
Sucrose does not reduce Tollens reagent and it cannot mutarotate because neither ring is in equilibrium with its open-chain aldehyde or ketone form.
It is more useful for on the other side because both units of the two sugars are glycosides.
Even though it is a nonreducing sugar, a reducing sugar ends.
Common names are not reliable.
The most common form of invert sugar is honey, a supersaturated mixture of sugars.
Tollens reagent reacts with formula C12H22O11 to form a silver mirror.
A b@galactosidase hydrolyzes it to d-galactose and d-mannose.
Propose a structure for something else.
The formula shows that this is a disaccharide.
Blood types O, A, B, andAB are linked by a b@galactosidase.
One of the hexoses must be in a free hemiacetal form since the original carbohydrate is a reducing sugar.
The surface of the red blood cells are made of Galactose.
The type O cells have no antigenic car.
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