Second Half I F24: Lecture Slides 58 - 74 Flashcards
What D-Sugars what are OH groups?
Left in Fischer Formula and Above in Haworth
Where is the Anomeric OH in Beta form?
Above Ring
Where is the Anomeric OH in Alpha Form?
Below Ring
How do you remember where the anomeric carbon is located?
LAB: Left —-> Above <—- Beta
What is the Carbonyl Carbon?
Always the electrophile in the reaction (will form the anomeric carbon)
What can any of the OH groups act as?
The nucleophile
What does which OH reacting with the Carbonyl C depend on?
The type of ring that is formed (pyranose or furanose)
What happens if the OH of carbon 6 is the nucleophile?
Fructose will form a 6-membered pyranose ring.
What is the anomeric carbon of a sugar?
An electrophile
What does the anomeric carbon being an electrophile make the sugar?
Reactive; at this positions most reactions involving ring forms of sugars take place.
What is the most important reaction of sugars?
The condensation of the anomeric carbon with the nucleophilic -OH of an alcohol or the -NH of an amine
What is the resulting molecule called?
A glycoside
What is the bond formed known as?
Glycosidic (C - O) or A glycosidic (C - N) bond
What happens if the anomeric carbon is associated in a glycosidic bond?
The sugar (in the ring form) can no longer open up to assume the linear form
What type of chains are able to undergo oxidation?
Open chain forms
What happens when the sugar can no longer open up to assume the linear form?
The sugar residue becomes a non-reducing sugar
What is a reducing sugar?
A free hydroxyl that is only found in linear form.
How are disaccharides formed?
When two monosaccharides are linked through a glycosidic bond.
How does a disaccharide reaction occur?
When the anomeric carbon (electrophile) of one sugar reacts with the hydroxyl group (nucleophile) of the other
What are Disaccharides?
Glycosides
How is Lactose formed?
The condensation of glucose with Galactose
What is Lactose named?
gal(B1 ->4)glc
How is the glycosidic bond of lactose formed?
The glycosidic bond is described as (B1 -> 4): going from C-1 of galactose in the B configuration to C-4 of glucose
Why can’t the anomeric carbon of galactose unable to undergo mutarotation?
It is involved in a glycosidic bond, therefore unable to form the linear form
What does the anomeric carbon in galactose become?
Non-reducing
What is the Anomeric Carbon in Glucose?
Free, therefore able to undergo mutarotation existing in either a(a-lactose), B(B-lactose) or linear forms
What is Lactose able to act as?
A reducing sugar
In disaccharides and polysaccharides, what is the end of a chain with a free anomeric carbon called?
Reducing End
What must the formation of the glycosidic bond of a disaccharide must involve?
The anaemic carbon of one sugar, because that is the only electrophilic C atom in a sugar.
What could galactose and glucose form?
Lots of different disaccharides besides lactose, making structural isomers of lactose.
What are the anomeric carbons of Glucose and Fructose involved in?
The glycosidic bond
What does both anaemic carbons being involved in the glycosidic bond mean?
Surcose is a non-reducing sugar.
What does Glucose and Fructose produce?
Sucrose
What is the Name of Maltose?
glc(a1-4)glc
What is Maltose?
Formed by the breakdown of starch
What is Trehalose?
glc(a1-a1)glc
*A non-reducing sugar
What are most carbohydrates?
Highly branched.
How is branching possible?
As sugars have several OH groups, each of which can act as the nucleophile in forming a glycosidic bond, bonding a single subunit to two (or more) others.
What are Homopolysacchardies?
Made from a single type of sugar monomer
What are heteropolysacchardies?
Made from two or more kinds of sugar monomers
