Monosaccharides

How are monosaccharides classified?

Based on the carbonyl group and the number of carbon atoms

What is the formula for monosaccharides?

CnH2nOn

What type of carbon chain do monosaccharides have?

Unbranched single bonded carbon chain

What is unique about the carbon atom in a monosaccharide?

One of the carbon atoms is double bonded to an oxygen making an carbonyl group, while the others have hydroxyl groups

What is an aldose?

A monosaccharide with an aldehyde functional group (carbonyl at end of carbon chain)

What is an example of an aldose?

Glyceraldehyde which is an aldotriose

What is a ketose?

A monosaccharide with a ketose functional group (carbonyl at middle of chain)

What is an example of a ketose?

Dihydroxyacetone which is a ketotriose

What is the most abundant monosaccharide?

D-glucose

How are aldose and ketoses structurally different?

Aldose: Has carbonyl group at end of carbon chain (aldehyde)

Ketose: Has carbonyl group at middle of carbon chain (ketone)

Give the category name and examples for monosaccharides that have:

• 3 carbons

• 4 carbons

• 5 carbons

• 6 carbons

• 7 carbons

• 9 carbons

3 carbons:

• Category name: Triose

• Example:

  • Glyceraldehyde (aldo)

  • Dihydroxyacetone (keto)

4 carbons

• Category name: Tetrose

• Example:

  • D-Erythrose

  • Erthyrulose

5 carbons

• Category name: Pentose

• Example:

  • D-arabinose, D-ribose

  • D-ribulose

6 carbons

• Category name: Hexose

• Example:

  • D-glucose, D-galactose, D-mannose

  • D-fructose

7 carbons

• Category name: Heptose

• Example: D-sedoheptulose

9 carbons

• Category name: Nonose

• Example: Neuraminic acid (sialic acid)

Function of these main monosaccharides

• D-glucose

• D-fructose

• D-galactose

• D-mannose

• D-sedoheptulose

D-glucose:

• Major energy source

• Sugar of blood

D-fructose: Sugar of seman, fetal blood, fruits

D-galactose: Sugar of milk

D-mannose: Composition of muscopolysaccharides

D-sedoheptulose: Intermediate in calvin cycle

What important function can monosaccharides do especially for diabetics?

Be sugar derivatives

Vitamin C as a monosaccharide

• Why is it an necessary for our diet?

• What animals can synthesise it?

• Function

• Lack in diet may cause

Necessary in diet: Because we cannot synthesize it

Animals that can synthesize vitamin C: Primates and guinea pigs

Function: Maintain health of dentine, cartilage, connective tissue and bone

Lack in diet may cause: Impairment of collagen formation