Carbohydrates

Question 1

General Formula of Carbohydrates

Answer 1

Cx(H2O)y

Question 2

Carbohydrate Functional Groups

Answer 2

Contains C=O (Aldehyde or Ketone group) and many -OH functional groups

Question 3

Aldehyde and Ketone

Answer 3

Aldehyde: R-C=O-H
Ketone: R-C=O-R

Question 4

Classification of Carbohydrates

Answer 4

• Size of base carbon chain
• No. of sugar units
• Location of C=O
• Stereochemistry

Question 5

Types of Carbohydrates

Answer 5

Monosaccharides: single sugar unit
Disaccharides: 2 sugar units
Oligosaccharides: 2-10 sugar units
Polysaccharides: >10 sugar units

Question 6

Carbohydrate Chains

Answer 6

Bridging of oxygen atoms to form glycosidic bonds

Question 7

Carbohydrate Functions

Answer 7

• Energy Metabolism
• Structure
• Precursor of DNA & RNA
• Cell Surface Marker

Question 8

Energy Metabolism

Answer 8

Fuel & Storage

Question 9

Carbohydrate Fuel

Answer 9

Glucose & it’s derivatives produce energy for immediate use by the organism

Question 10

Carbohydrate Storage

Answer 10

Starch is stored by plants while glycogen is stored in the liver & muscles of animals for later use

Question 11

Carbohydrate Structural Use

Answer 11

• Scaffolding of bacterial and plant cell wall
• Exoskeleton shell of arthropods
• Lubricative coating for cells

Question 12

Carbohydrate Precursors of DNA & RNA

Answer 12

• Serves a chemical structural role

- Polar sites for the catalytic processes of RNA

Question 13

Ribose & Deoxyribose sugars

Answer 13

• Monosaccharides

- Vital for the synthesis of nucleic acids RNA & DNA

Question 14

Carbohydrates Cell Surface Markers (4 pts) [1]

Answer 14

• Markers for recognition by other biomolecules when carbohydrates covalently bond with other proteins & complex lipids
• Immune protection/ recognition

Question 15

Carbohydrates Cell Surface Markers (4 pts) [2]

Answer 15

• Cell-Cell Recognition

- Host Pathogen Interaction

Question 16

Monosaccharides

Answer 16

• Hydrogen bonding with OH groups
• High mp
• Water-soluble
• Insoluble in non-polar solvents
• Optical isomers are D-Sugars
• Sweet tasting
• Chiral
• Cyclic structure

Question 17

D-Sugar and L-Sugar

Answer 17

D-Sugar: OH on the right
L-Sugar: OH on the left
*Locate chiral centre furthest from C=O

Question 18

α & β glucose

Answer 18

α glucose: opposite sides
β glucose: same side
*Ring form

Question 19

Carbohydrate Chemical features

Answer 19

• Have at least 1, often >2 asymmetric centres
• Exists in either linear or ring structure
• Able to form polymers via glycosidic bonds
• Able to form multiple H bonds with H2O

Question 20

Glucose & Monosaccharide reactions

Answer 20

• Redox
• Esterification
• Amino Derivative
• Glycoside Formation

Question 21

Testing for Reducing Sugars

Answer 21

Benedict's Test 
1. Add Benedict's solution to test solution
2. Gently heat to boil
Red Precipitate: Reducing Sugar present
*Colour varies with sugar concentration

Question 22

Esterification

Answer 22

Esters formed when hydroxyl groups (alcohols) react with acids

Question 23

β-Maltose

Answer 23

-α-D-glucose and β-D-glucose, α (1 -> 4) linkage.

Question 24

Polysaccharides

Answer 24

• Carbohydrate Polymers
• Storage Polysaccharides
• Structural Polysaccharides
• Structural Peptidoglycans

Question 25

Cellobiose

Answer 25

• β-D-glucose and β-D-glucose, β (1 -> 4) linkage.

- Unuseable since we lack enzymes to hydrolyze

Question 26

Lactose

Answer 26

-β-D-galactose and β-D-glucose, β (1 -> 4) linkage

Question 27

Sucrose

Answer 27

α-glucose and β-fructose, α (1 -> 2) linkage