POLYSACCHARIDES From Greek:

Poly meaning manySacchar meaning sugarAre made from sugars

Carbohydrates/sugars:Are the fuel and building blocks for lifeAre building blocks (monomers) for

polysaccharidesExamples monosaccharides:

GlucoseFructose

GlucoseThe most common monosaccharide,

glucose – C6H12O6, is of central importance in the chemistry of life

SynthesisLinking monosaccharides (sugars) together

Dehydration synthesis process:

Key Characteristics of Sugars

1. They are hydrocarbons with carbonyl groups (C=O) and multiple hydroxyl groups (OH)

2. Carbon skeletons are 3 to 7 carbons long.

3. Their names end in the suffix “ose”.

Ketose vs Aldose4. If the carbonyl group is in the middle of

the chain it is classified as a ketose, and if it is on the end of a chain as an aldose.

5.Small differences in structure can cause major differences in the behaviour and shape of the sugar

Galactose and glucose are optical isomers (same number and types of atoms, different properties).

Galactose is not very water-soluble therefore is not easily absorbed – is not digested

6.When in water (aqueous solution) most sugars form rings.

Example: Glucose

Chemical equilibrium between the linear and ring structure favors the ring structure.

Naming sugars:1. Prefixes of: Mono, di, tri, … poly

Mono is a single sugarDi = two sugars joinedTri = three sugars joinedPoly = many sugars joined

2. Depending on the size of a carbon skeleton (ranges from 3 – 7), monosaccharides are named as:

Trios – 3 carbon chainTetrose – 4 carbon chainPentose – 5 carbon chainHexose – 6 carbon chainHeptose – 7 carbon chain

3. Aldose vs. Ketose (See earlier notes)

Forming name: (keto-/aldo-) + (# of carbons) + -ose

Examplesa monosaccharide that contains an

aldehyde and three carbons is formed in this way:

aldo- + tri + ose ------> aldotriosea five carbon sugar that contains a ketone

is called a ketopentose.

TASKWorksheet questions 1 - 9