Monosccharides, Disaccharides, Polysaccharides

Macromolecule= A 'giant molecule' there are three types of macromolecule in living organisms, polysaccharides, polypeptides (proteins) and nucleic acids.

Polymer= Substance composed of macromolecules.

Monomer= A molecule that can be bonded to other identical molecules to form a polymer.

There are two types of glucose:

To remember which way the -OH group goes remember ABBA:

Alpha

Below

Beta

Above

Glycosidic bonds:

alpha glucose= Forms between the 1st carbon and 4th carbon so is an alpha 1-4 glycosidic bond

Beta glucose= It is the same as alpha glucose but every other monomer is inverted as the -OH group is inverted

Breakage of glycosidic bonds is known as hydrolysis (breakage by water).

Monosaccharides:

• Soluble in water 
• Vary according to the number of carbon atoms it contains.
• 3 types you need to know: 

1. Glucose
2. Fructose
3. Galactose

Disaccharides:

• Sugars composed of 2 monosaccharides covalently bonded by a glycosidic linkage
• Water soluble
• 3 types you need to know:

1. Maltose (Glucose+Glucose)
2. Lactose (Glucose+Galactose)
3. Sucrose (Glucose+Fructose)

Polysaccharides:

Carbohydrates whose molecules consist of a number of sugar molecules bonded together.

1. Glycogen

• Insoluble storage polysaccharide (in animals)
• Stored in: liver, muscles
• Monomer: alpha glucose
• Bonds: a 1-4 glycosidic linkage/a 1-6 glycosidic linkage
• Structure: branched every 12 monomers

2. Starch

Amylopectin (80%)

• Insoluble storage polysaccharide (in plants)
• Monomer: alpha glucose
• Bonds: a 1-4 glycosidic linkage/a 1-6 glycosidic linkage
• Structure: large branched structure with branches every 20 monomers

Amylose (20%)

• Monomer: alpha glucose
• Bonds: a 1-4 glycosidic linkage (and H-bonds)
• Structure: long-chain alpha helix (right-handed coil) stabalised by H-bonds

3. Cellulose

• Cellulose macrofibrils form plant cell walls
• Monomer: Beta glucose
• Bonds:β 1:4 glycosidic linkage
• Structure: Every 2nd β-monomer is inverted causing the cellulose molecule to remain straight

Microfibrils= Cellulose molecules are linked together by H-bonds (causing high tensile strength)

Macrofibrils= Microfibrils bonded together by H-bonds.