Biological Molecules

This lesson covers the key biological molecules — carbohydrates, lipids, proteins and DNA — as required by the Edexcel GCSE Biology specification (1BI0), Topic 1: Key Concepts in Biology. You need to know the structure, function and chemical tests for each type of molecule.

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Overview

All living organisms are made from a relatively small number of chemical elements, mainly carbon (C), hydrogen (H), oxygen (O) and nitrogen (N), with smaller amounts of sulfur (S) and phosphorus (P).

These elements combine to form four main types of biological molecule:

1. Carbohydrates — made of carbon, hydrogen and oxygen
2. Lipids (fats and oils) — made of carbon, hydrogen and oxygen
3. Proteins — made of carbon, hydrogen, oxygen, nitrogen (and sometimes sulfur)
4. Nucleic acids (DNA) — made of carbon, hydrogen, oxygen, nitrogen and phosphorus

Exam Tip: You need to know the basic structure, function, and chemical test for each biological molecule. This is a common exam topic worth several marks.

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Carbohydrates

Carbohydrates are molecules made of carbon, hydrogen and oxygen. They are used primarily as a source of energy and for energy storage.

Types of Carbohydrate