BGM1002/L10 Carbohydrates I

Question 1

Give 3 functions of carbohydrates.

Answer 1

Storage/energy transport
Cell-cell communication/adhesion
Host-pathogen/symbiont interactions
Structural components
In DNA and RNA

Question 2

What elements do carbohydrates consist of?

Answer 2

C, H, O
Some contain S and/or N

Question 3

What is the empirical formula of carbohydrates?

Answer 3

(CH2O)n

Question 4

How many hydroxyl groups do carbohydrates contain?

Answer 4

2+

Question 5

What other names are given to carbohydrates?

Answer 5

Sugars
Saccharides
Glycans

Question 6

What are the two simplest carbohydrates and how many carbons do they contain?

Answer 6

Glyceraldehyde
Dihydroxyacetone
3 carbons

Question 7

How many stereoisomers does glyceraldehyde have?

Answer 7

2 (1 asymmetric carbon)

Question 8

How many different groups are chirally active carbons attached to?

Answer 8

4

Question 9

Which has more asymmetric carbons: aldoses, or ketoses?

Answer 9

Aldoses (+1)

Question 10

Which carbon is referred to as C1 in a) aldoses and b) ketoses?

Answer 10

a) aldehyde
b) carbonyl

Question 11

How many carbons do most sugar rings have?

Answer 11

4-5

Question 12

What is a pyranose sugar?

Answer 12

A 6-membered ring (as it appears similar to pyran)

Question 13

What configuration do sugar rings usually take?

Answer 13

Non-planar ‘chair’ configuration

Question 14

What two orientations can substituents on ring C atoms hold?

Answer 14

Axial or equitorial

Question 15

What is the difference between alpha and beta rings?

Answer 15

Alpha - C1 and C5 have same stereochemistry
Beta - C1 and C5 have different stereochemistry

Question 16

What is the difference between D and L stereoisomers?

Answer 16

L has left-handedness
D has right-handedness

Question 17

What isomer form do most sugars take?

Answer 17

D-form

Question 18

Define epimers.

Answer 18

When asymmetric carbon 2, 3 or 4 is in a different configuration to glucose, resulting in a different sugar

Question 19

Define oligosaccharide.

Answer 19

A sugar of 2-10 monosaccharides

Question 20

Define polysaccharide.

Answer 20

A sugar of 10+ monosaccharides

Question 21

What bond forms between monosaccharides?

Answer 21

Covalent glycosidic bond

Question 22

What groups do glycosidic bonds form between?

Answer 22

Hemiacetal and hydroxyl or non-sugar hydroxyl
-NH
-SH

Question 23

What is an alpha configured glycosidic bond?

Answer 23

C1,4 bond in alpha molecules