Carbohydrates

Question 1

Name of this aldohexose?

Answer 1

D glucose

-reference carbon (C5) has OH group on the right, therefore it is a D configuration

Question 2

Name this ketohexose?

Answer 2

D fructose

-reference carbon (C5) has OH group on the right, therefore it is a D configuration

Question 3

Name this aldopnetose?

Answer 3

D ribose

-reference carbon (C4) has OH group on the right, therefore it is a D configuration

Question 4

Name this aldohexose?

Answer 4

D galactose

-reference carbon (C5) has OH group on the right, therefore it is a D configuration

Question 5

Which D-aldohexoses are epimers at C4?

Answer 5

D-glucose and D-galactose

Question 6

Which carbon is chiral in monosaccharides?

Answer 6

C2 in aldehydes

C3 in ketones (except dihydroxyacetone which has no chiral corbon)

Question 7

Which carbon is the reference carbon in monosaccharides?

Answer 7

The second to last carbon containing the -OH furthest from aldehyde/ketone

Question 8

What molecule forms when D-glucose is oxidized at C6?

Answer 8

glucuronic acid

This reaction requires an enzyme

The molecule ionizes at physiologic pH

Question 9

The chemical modification where terminal carbon’s hydroxyl group has been oxidized to a carboxylic acid forms what?

Answer 9

uronic acid

Ex: glucose ⇒glucuronic acid

it ionizes to negative charge at physiologic pH making it more water soluable

Question 10

Chemical modification where carbonyl carbon of an aldose is oxidized forms what?

Answer 10

aldonic acid

Ex: D-glucose ⇒ D-gluconic acid

it ionizes to negative charge at physiologic pH making it more water soluable

Question 11

What chemical properties of the anomeric carbon occur as the result of a monosaccharide cyclization?

Answer 11

• The anomeric carbon becomes chiral (α has OH pointing down, ß has OH pointing up)
• It is now bonded to 2 electronegative oxygens, giving it a larger partial positive than any other carbon in the cyclic structure