CARBOHYDRATES - KEY NOTES

Contain Elements: Carbon, Hydrogen and Oxygen.

CLASSIFICATION: The basic sugar unit = the saccharide

• 1 sugar unit = Monosaccaride
• 2 sugar units = Disaccharide
• Many sugar units = Polysaccharide

MONOSACCHARIDES

Examples of Monosaccharides: Glucose, Ribose

General There are the building blocks of other important C/H’s

Monosaccharides are:

• Sweet tasting
• Soluble in water
• Reducing sugars (see below)

Reducing Sugar Properties (all monosaccharides are reducing sugars). M/S are capable of REDUCING benedicts solution. When this reduction occurs benedicts solution changes from blue to orange/red.

DISACCHARIDES

Examples of D/S: Maltose (Malt sugar), Lactose (milk sugar)

Maltose formed by CONDENSATION of 2 units of glucose, the bond is called a glycosidic bond.

Note: In the exam you could be given half of the reaction below and asked to fill in the other half - you wouldn't be asked to come up with it all off the top of your head

2 molecules of glucose
	+
Undergo a condensation reaction to form…
+ H2O
Maltose and Water

General Summary of disaccharides

• May be non-reducing
• Sweet tasting
• Water soluble

POLYSACCHARIDES

Examples of P/S: Starch, Glycogen, Cellulose

These are an important group of carbohydrates. Two main divisions:

• Structural Polysaccharides e.g. Cellulose, Chitin, Lignin (wood)
• Storage Polysaccharides e.g. Starch and Glycogen

General Properties of P/S

• Non sweet tasting
• Non truly soluble in H₂O

Structural P/S

In these polysaccharides the sugar unit residues present in long chain molecules of the polymer are straight, and cross-linkages between chains occur giving the material its strength.