A-Level Biology Specification

AQA 7402

Section 1.2: Carbohydrates

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#1.2.1

Monosaccharides are the monomers from which larger carbohydrates are made. Glucose, galactose and fructose are common monosaccharides.

#1.2.2

A condensation reaction between two monosaccharides forms a glycosidic bond.

#1.2.3

Disaccharides are formed by the condensation of two monosaccharides:

- maltose is a disaccharide formed by condensation of two glucose molecules
- sucrose is a disaccharide formed by condensation of a glucose molecule and a fructose molecule
- lactose is a disaccharide formed by condensation of a glucose molecule and a galactose molecule.

#1.2.4

Glucose has two isomers, α-glucose and β-glucose, with structures:

#1.2.5

Polysaccharides are formed by the condensation of many glucose units.

- Glycogen and starch are formed by the condensation of α-glucose.
- Cellulose is formed by the condensation of β-glucose.

#1.2.6

The basic structure and functions of glycogen, starch and cellulose. The relationship of structure to function of these substances in animal cells and plant cells.

#1.2.7

Biochemical tests using Benedict's solution for reducing sugars and non-reducing sugars and iodine/potassium iodide for starch.