Carbohydrates

Question 1

monosaccharides

Answer 1

simple sugars that can’t be hydrolyzed into simpler sugars.

ex. glucose

Question 2

polysaccharides

Answer 2

combination of many monosaccharides in a chain

ex. cellulose

Question 3

need hand done cards for D-fructose, D-glucose, D-galactose, D-mannose

Answer 3

g

Question 4

What are D- and L- sugars?

Answer 4

enantiomers

Question 5

epimers

Answer 5

diastereomers that differ at only 1 chiral center

Question 6

What is the mechanism for hemiacetal/hemiketal formation?

Answer 6

acetylaldehyde (an acetal) is attacked at the carbonyl carbon by an alcohol, then the carbonyl O- takes a hydrogen from the added alcohol.

hemiketal formation is the same, but starting with a ketone and an alcohol

Question 7

sugar cyclization

Answer 7

sugar internally forms a hemiacetal - OH from one side of the sugar attacks the carbonyl carbon on the other side of the sugar.

Question 8

pyranose

Answer 8

6-carbon sugar ring

stable

common in nature

Question 9

furanose

Answer 9

5-membered sugar ring

OH on the 5th carbon attacks the carbonyl rather than the 6th OH.

less stable than pyraoses

Question 10

anomers

Answer 10

C-1 epimers

C-1 OH points down in alpha anomer, C-1 OH points up in beta epimer

Question 11

mutarotation

Answer 11

alpha D-glucose can uncyclize, forming a straight-chain sugar, then recyclize, either reforming alpha D-glucose, or forming beta D-glucose.

Question 12

What is the product of a monosaccharide being oxidized?

Answer 12

a ketone forms on the ring - becomes a lactone

Question 13

Benedict’s reagent produces what when a reducing sugar is treated with it?

what is the intermediate?

Answer 13

forms a straight-chain carboxylic acid.

intermediate is an aldose

Question 14

Why are aldoses reducing sugars?

Answer 14

can be oxidized - have room for another O to be added.