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Macromolecules

Very large molecules, often formed by the polymerisation of smaller subunits

Protein

A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.

Glossary

A list of often difficult or specialised words with their definitions.

Melanin

Dark brown or black pigment found in the skin, hair and irises of the eyes. The skin produces more melanin when exposed to the sun.

Lipid

Molecules which contain a lot of stored energy built up of fatty acids and glycerol. Lipids include oils and fats

Albino

A person with little or no pigment in the eyes, skin and hair. They have inherited an altered copy of a gene that does not work properly and so the body does not make the usual amounts of melanin.

Cell

The basic unit from which all living organisms are built up, consisting of a cell membrane surrounding cytoplasm and a nucleus.

Ions

Charge particles formed when an atom loses or gains electrons during the formation of ionic bonds

DNA

Deoxyribonucleic acid. This is the molecule which contains the genetic code. It coils up tightly inside chromosomes. DNA is a double helix made from two strands which are joined together by pairs of bases.

Adenosine triphosphate

Molecule which acts as the common energy currency in all cells, providing the energy needed to drive chemical reactions in cells.

The importance of chemistry in biology

Why does your skin wrinkle as you get older? If you have osteogenesis imperfecta, why do your bones break so easily? Why do albino rabbits have pink eyes? The answer to all of these questions, at the most basic level, is chemistry!

Biology is the study of living things. The key to understanding biology is to understand the fundamental chemistry which underpins all life.

In young skin collagen molecules form elastic triple helices which stretch as the skin moves. With age, the molecular structure changes to become more rigid, brittle and more likely to tear. When collagen combines with bone it gives it tensile strength, like reinforced concrete. In osteogenesis imperfecta, the collagen and bone don’t combine so the bone is brittle and breaks easily. And an albino rabbit lacks one single molecule called melanin.

The chemistry of life begins with the basic principles of bond formation and bond breaking, and the nature of the different compounds formed. Life revolves around the balancing act between the energy released as bonds are broken and the energy taken in as bonds are formed.

Life on earth depends on the nature of the carbon atom and the nature of water. Water is fundamental to life and understanding the properties of water helps to make sense of many other areas of biology.

Whilst many small molecules and ions play vital roles in cells and organisms, macromolecules are also key. An understanding of the chemistry of compounds including carbohydrates, proteins, lipids, ATP, DNA and RNA gives you the tools you need to make sense of everything from cell biology to ecology.

Mouse on some leaves

Each organism is a collection of carefully controlled chemical reactions

Photos by Anthony Short unless credited otherwise. Animations and diagrams by Edward Fullick throughout.

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