Unit 2 - B Biological Molecules

AS LEVEL
B I O LO GY

,2 Biological molecules .............................................3

2.1 Testing for biological molecules ....................................3
2.2 Carbohydrates and lipids .............................................6
Ring structures .............................................................6

Monomers, polymers and macromolecules ....................7
Carbohydrates ............................................................7
Lipids ........................................................................12
2.3 Proteins and water .....................................................14

Proteins .....................................................................15
Water .......................................................................24

, 2 BIOLOGICAL
MOLECULES
2 .1 T E S T I N G F O R B I O L O G
MOLECULES
Tests for biological molecules can be used in a variety of contexts, such as
contents of mixtures of molecules and following the activity of digestive enz


LEARNING OUTCOMES

C ANDIDATES SHOULD BE ABLE TO:

A. carry out tests for reducing sugars and non-reducing sugars, the iodine
iodide solution test for starch, the emulsion test for lipids and the biuret
to identify the contents of solutions


1. Testing for the presence of reducing sugars

I. Background information

- The reducing sugars include all monosaccharides, such as glucose, and som
disaccharides, such as maltose; the only common non-reducing sugar is su

- Reducing sugars are so called because they can carry out a type of chemica
known as reduction; in the process they are oxidized. This is made use o
Benedict’s test using Benedict’s reagent; Benedict’s reagent is copper (I
an alkaline solution and has a distinctive blue colour. Reducing sugars red
copper sulphate, containing copper (II) ions, to insoluble brick-red copper
containing copper(I); the copper oxide is seen as a brick-red precipitate.