Diabetes (advanced level)
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Discovery of 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
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.
Insulin
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.
Molecular model of insulin molecule, ribbon
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.
