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Non-animal alternatives

Processes such as cell culture, computer modelling, imaging and microdosing of human volunteers that can give information on potential harmful effects of a substance

X-ray crystallography

A technique that uses the diffraction of X-rays to determine the molecular structure of a crystalline substance.

Hydrogen bond

An intermolecular attractive force between hydrogen, when it is covalently bonded to a highly electronegative atom (fluorine, oxygen or nitrogen), and an oxygen, nitrogen or fluorine atom on another molecule.


A long chain of hundreds or even thousands of amino acids joined by peptide bonds.

Home Office

The UK government department responsible for regulating the use of animals in scientific research.

Amino acid

The basic building blocks of proteins. There are twenty amino acids used, in different combinations, to make every protein required by the human body.

Discovery of Insulin

Person injecting insulin

Injecting insulin allows individuals with diabetes to control their blood sugar levels.

In 1921 two researchers, Fred Banting and Charles Best, were the first to discover insulin and use it to treat diabetes.

Animal Testing

At the time that Banting and Best were looking for a cure for diabetes, there were no alternatives but to perform their experiments using animals.

To test their theory Banting and Best used 10 dogs. They made the dogs diabetic and then investigated treatments for the diabetes. The result of their research has saved the lives of millions of people.

Banting and Best's discovery of insulin

Investigations using isolated insulin from dog pancreas

Some people have very strong opinions about testing medicines on animals. Today the use of animals is very tightly regulated and only allowed in circumstances where there are no other viable alternatives. Decide on a set of rules that should govern whether testing can take place or not.

Click here to see what the current UK law says about animal research.


Banting and Best did not know the chemical structure of insulin. In 1955, Fred Sanger determined its amino acid structure and in 1969, Dorothy Hodgkin used X-ray crystallography to find its three-dimensional structure.

The insulin molecule acts by attaching to cell-surface receptors on its target cells. Its three-dimensional structure enables it to attach to these receptors. The shape of the insulin molecule is determined by the way the protein chains fold around each other due to hydrogen bonds and disulfide bridges.

Insulin is a protein made up of two amino acid chains.

Chemical structure of insulin
3-d model of insulin

Molecular model of insulin molecule, ribbon

3-d model of insulin

This model shows the three-dimensional structure of insulin. It is a complex protein hormone

Image courtesy of: T. Blundell & N. Campillo / Wellcome Images

Protein structure

The three dimensional structure of protein is described using four categories:

  • Primary
    Amino acid sequence of the polypeptide chain. e.g. amino acids in insulin's A and B chains.
  • Secondary
    How the amino acid chain folds back onto itself. Typically beta sheets or alpha helices.
  • Tertiary
    Folds in the beta sheets or helixes to give overall structure of the polypeptide chain.
  • Quaternary
    Some proteins are made of more than one polypeptide chain. These are joined to make the functioning protein. e.g. insulin's A and B chains are joined by disulfide bridges.