Ch. 4: Carbohydrate Structure and Function

Question 1

monosaccharides

Answer 1

the most basic carbohydrate units containing a hydroxyl group (nucleophile) and a carbonyl group (electrophile)...
triose - three carbons
tetrose - four
pentose - five
hexose - six

Question 2

aldoses

Answer 2

carbohydrates that contain an aldehyde group as their most oxidized functional group. Aldehyde is always on C1.

Question 3

ketoses

Answer 3

carbohydrates that contain a ketone group as their most oxidized functional group. Ketone is almost always on C2.

Question 4

glycosidic linkages

Answer 4

type of linkage formed in part by the aldehyde/ketone group on a sugar

Question 5

number of stereoisomers with a common backbone

Answer 5

2^n where n is the number of chiral molecules in the compound

Question 6

In a Fischer projection, D-sugars have the hydroxide of their highest-numbered chiral center on which side of the diagram?

Answer 6

The right side

Question 7

In a Fischer projection, L-sugars have the hydroxide of their highest-numbered chiral center on which side of the diagram?

Answer 7

The L side

Question 8

Enantiomers have opposite configurations of how many chiral centers

Answer 8

All chiral centers on enantiomers will have opposite configuration of each other (L on A is configured as D on B)

Question 9

Two sugars in the same family (aldose/ketose, same # or carbons) that are not identical and not mirror images of each other are called

Answer 9

diastereomers

Question 10

Two sugars that differ in configuration at exactly one chiral center are called

Answer 10

epimers

Question 11

hemiacetals

Answer 11

cyclic structure formed from an intramolecular rxn of an aldose monosaccharide

Question 12

hemiketals

Answer 12

cyclic structure formed from an intramolecular rxn of an ketose monosaccharide

Question 13

pyranose ring

Answer 13

six-membered ring

Question 14

furanose ring

Answer 14

five-membered ring

Question 15

anomeric carbon

Answer 15

carbonyl carbon of a monosaccharide that becomes chiral during ring formation

Question 16

anomers

Answer 16

molecules that differ in conformation at the anomeric carbon

Question 17

alpha-anomer

Answer 17

-OH group on the C1 trans to the -CH2OH substituent

less favored when in solution d/t hydroxyl group on the anomeric carbon being axial, adding to steric strain

alpha, apart

Question 18

beta-anomer

Answer 18

-OH group on the C1 cis to the -CH2OH substituent

beta, better together

Question 19

mutarotation

Answer 19

interconversion between the alpha and beta anomers via ring opening and reclosing when exposed to water.

Question 20

aldonic acids

Answer 20

aldehyde that has been oxidized (while in chain form) to a carbonic acid

Question 21

reducing sugar

Answer 21

any monosaccharide with a hemiacetal ring because aldoses can be oxidized

ketones are also reducing sugars because they can tautomerize to aldose under basic conditions

Question 22

lactone

Answer 22

a cyclic ester with a carbonyl group on the anomeric carbon produced when an aldose is oxidized in ring form

Question 23

two reagents used to detect the presence of reducing sugars

Answer 23

Tollens’ reagent (silvery mirror) and Benedict’s reagent (reddish precipitate)

Question 24

Glycosides are formed when hemiacetals react with what

Answer 24

alcohol

anomeric hydroxyl group –> alkoxy group with mix of alpha and beta acetals and H2O as a leaving group. Equivalent rxn occurs with hemiketals forming ketals

Question 25

Disaccharides and polysaccharides forms as a result of what kind of bonds between monosaccharides

Answer 25

glycosidic bonds formed during dehydration reactions

Question 26

linkages between sugar molecules are named for what two things

Answer 26

1. configuration of the anomeric carbon
2. the numbers of the hydroxyl containing carbons involved in the linkage

configuration of the second anomeric carbon is not included in the name when it is not involved in the bond

Question 27

homopolysaccharide

Answer 27

a polysaccharide made up of only one type of monosaccharide

Question 28

heteropolysaccharide

Answer 28

a polysaccharide made up of only 2+ types of monosaccharides