Chapter 4 Flashcards
What is mutarotation?
The spontaneous cycling of the alpha and beta anomer forms of a sugar molecule. This results in a mixture of both snorers at equilibrium, with beta configuration being dominant as it is more stable in the chair conformation.
In a monosaccharide which group serves as the nucleophile?
Hydroxyl group
In a monosaccharide which group serves as the electrophile?
Carbonyl group
In a Fischer projection, the horizontal lines are considered (out of the page/ into the page).
Out of the page
In a Fischer projection, the vertical lines are considered (out of the page/ into the page).
Into the page
Shortcut to figure out # of stereoisomers for a monosaccharide.
2^n; n = number of chiral carbons in molecule
Enantiomers are ______?
Stereoisomers which are nonsuperimposable mirror images of each other.
Diastereoisomers are _____?
Stereoisomers which are not mirror images, but have the same chemical formula and same connectivity.
What are epimers?
A type of diastereomer where the connectivity in space only differs for 1 chiral carbon.
How can you tell if a monosaccharide is D or L by looking at a Fischer projection?
If it is D, the OH on last chiral C points to the right.
If it is L, the OH on last chiral C points to the left.
A glycosidic linkage occurs between
The anomeric carbon on the first sugar and any carbon on the second sugar (2,3,4,6 etc)
Are D-glucose and D-fructose considered diastereomers (stereoisomers)?
No, they are not diastereoisomers/stereoisomers because they have different connectivity in space, that is the carbonyl group (double bond) is located at different C’s. Fructose is a ketose, while glucose is an aldose.
What is the difference between stereoisomers and constitutional isomers?
Stereoisomers have the same chemical formula and same connectivity in space.
Constitutional isomers have the same chemical formula, but different connectivity.
Name some examples of hexose sugars.
Fructose, glucose, galactose, and mannose
An aldose usually forms what kind of cyclic ring?
6 membered pyranose ring.
A ketose usually forms what kind of cyclic ring?
5 membered furanose ring
When converting a Fischer projection into a Haworth, how do you determine if the last C (CH2OH) group is pointing up or down?
You take the opposite of the direction of OH group on the previous carbon. For example, if the OH is on the right, OH would be down. Meaning the CH2OH would be left and up.
Name the three important polysaccharides.
Cellulose, starch, and glycogen
What monosaccharide are the three polysaccharides (cellulose, starch, glycogen) composed of?
D-glucose
What is the more stable form of glucose, alpha or beta?
Beta glucose because the OH on the anomeric 1st C that is pointing up is in the equatorial position which produces less steric hinderance.
Describe characteristics of cellulose
-Composed of beta-D-glucose molecules linked by beta 1,4 glycosidic bonds
-indigestible by humans
-Used by humans as fiber to draw water into the gut
Describe characteristics of starch.
-Composed of alpha-D-glucose monosaccharides
-Is digestible by humans
-Further subdivided into amylose and amylopectin
-Used as a source of energy by humans
Difference in structure between amylose and amylopectin
Amylose is made of a linear chain of D-glucose monomers linked by alpha-1,4 glycosidic bonds
Amylopectin is not linear; contains both linear chain of glucose monomers linked by alpha-1,4 glycosidic bonds and branches via alpha-1,6 glycosidic bonds.
What are some stereoisomers of D-glucose?
D-galactose and D-mannose
