Monosaccharides, Disaccharides and Polysaccharides Flashcards
What is a glycosidic bond?
A bond that links a sugar to another molecule.
Ketoses may have the ability to act as reducing sugars. Which process explains this?
Tautomerization
(A rearrangement of bonds, which allows ketoses to undergo keto-enol shifts. This forms aldoses, which can then act as reducing sugars.)
How are glycosidic bonds broken?
Hydrolysis
What are three of the most important disaccharides?
- sucrose
- maltose
- lactose
Which disaccharide(s) are NOT reducing sugars?
Sucrose
Which disaccharide(s) are reducing sugars?
- Maltose
- Lactose
Why is sucrose NOT a reducing sugar?
Because it has NO free hydroxyl (OH) group at its anomeric carbon.
How are disaccharides formed?
The -OH group on the anomeric carbon of one sugar reacts with the -OH group on another sugar to form an acetal (or ketal).
What are three of the most important polysaccharides?
- cellulose (unbranched)
- starch
- glycogen (highly branched)
They are all polymers of the same monosaccharide, D-glucose.
Which polysaccharide is indigestable by humans? Why?
Cellulose
(contains beta linkages which humans do NOT have the enzymes to digest.)
Which kind of linkages/glycosidic bonds are found in cellulose?
β-1, 4 glycosidic linkages
Cellulose is the ONLY polysaccharide with beta linkages!
Which kind of linkages/glycosidic bonds are found in starch?
α-1, 4 glycosidic linkages
Which kind of linkages/glycosidic bonds are found in glycogen?
α-1, 4 with additional α-1, 6 glycosidic linkages
What are two main types of starches?
- amylose (unbranched and linear α-1, 4 linkages)
- amylopectin (branched α-1, 4 and 1,6 linkages)
Which polysaccharide functions as an energy storage unit in animals?
Glycogen
