Diabetes (Advanced Level)

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Making human insulin

For many years, insulin was obtained by purifying it from the pancreas of cows and pigs slaughtered for food. This was expensive and time consuming.

Insulin is now made by genetically-engineered microbes. This enables human insulin to be produced in large quantities and then purified.

Insulin gene

The amino acid sequence of insulin was found in 1955. Knowing this sequence, and understanding the triplet code for the bases on DNA, has allowed researchers to synthesise the gene for human insulin. This could then be used to genetically modify bacteria to produce human insulin.

Use the information in the table to produce the DNA base sequence for the first three amino acids of the insulin A-chain.

Genetic code

A sequence of three DNA bases (triplet) code for one amino acid.

amino acid	1st base	2nd base	3rd base
valine	G	T	T
isoleucine	A	T	T
glycine	G	G	C

Drag the bases into the correct sequences to form the amino acid chain

	DNA sequence	amino acid chain
adenine cytosine guanine guanine guanine thymine thymine thymine thymine

Genetic engineering to make human insulin

The animation shows an overview of how genetic engineering can be used to produce human insulin. The enzymes involved are shown in the lower animation.

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Details of the enzymes involved.

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Producing human insulin

Human insulin is produced in a very controlled and sterile environment.

Genetically-engineered bacteria are grown in large stainless steel fermentation vessels. The vessel contains all the nutrients needed for growth.

When the fermentation is complete, the mixture containing the bacteria is removed from the fermentation vessel. The bacteria are filtered off and broken open to release the insulin they have produced. The insulin is separated from all the other proteins and organelles from inside the bacteria and once purified it is packaged for distribution.

All the equipment is kept sterile to prevent contamination and regular checks make sure that the insulin meets the required quality standards.

Fermentation vessel in a factory

Production and packaging of insulin pens

Insulin pens

Images courtesy of Novo Nordisk

Question 6

Drag these processes into the correct order for making human insulin from genetically engineered bacteria.

Put genetically-engtineered bacteria into fermentation vessels

Allow genetically-engineered bacteria to grow

Harvest bacteria and break open to release insulin

Clean fermentation vessel and add solution containing nutrients

Purify and package human insulin

Insert gene for human insulin into bacteria

Acarbose

This type 2 diabetes medication is not much used now.

Amino acids

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

ATP (adenosine triphosphate)

A small organic non-protein molecule that is a source of chemical energy within a cell.

Autoimmune disease

A disorder where the body's immune system behaves abnormally and starts attacking its own cells

Autopsies

The study of the human body to investigate how a disease or injury leads to death

Cardiovascular disorders

Diseases linked to the heart and its blood vessels, for example heart disease and stroke

Diabetic ketoacidosis (DKA)

When glucose is high in the blood but unable to enter cells, the body starts using stores of fat for energy, which results in the production of acidic ketones as a by-product. If ketone levels rise unchecked a hyperglycaemic coma can result which may be fatal.

Disulfide bridge

A covalent S-S bond that joins two cysteine amino acids together, also called an SS-bond or disulfide bond.

Duodenum

Within the human body this is the first 25 - 30cm long section of the small intestine.

Embryo

The name for a group of cells that are developing into a foetus. In humans this is from implantation to the 8th week of development

Endocrine gland

A gland which secretes hormones straight into the bloodstream rather into the blood via a tube or duct.

Enzyme

Biological catalysts that speed up chemical reactions.

Exocrine cells

Cells found in the exocrine glands that secrete hormones into ducts, as opposed to straight into the bloodstream.

Fermentation

Process where microorganisms are cultured so that they reproduce and increase in quantity

Fatty acid

Large molecule consisting of a carboxylic acid (RCOOH) with the 'R' being a long unbranched hydrocarbon chain.

Gastrointestinal

Relating to the body's digestive system, including the stomach and intestines.

Gene

A short piece of DNA which is responsible for the inheritance of a particular characteristic. It codes for the production of a specific protein

Gene therapy

A new, experimental method of fighting disease by replacing a defective gene with a healthy gene

Genetic engineering

A general name for the processes which scientists use to produce desired characteristics or substances that are in short supply, such as human insulin

Glucagon

A hormone produced by the pancreas. It causes the liver to convert glycogen back to glucose and to release glucose into the bloodstream.

Glucose

A type of sugar: a monosaccharide with 6 carbon atoms (a hexose sugar)

Glycogen

A polysaccharide,
(C ₆ H ₁₀ O ₅ ) _n , that is stored in the liver and in muscles and can be converted back into glucose when needed by the body.

Harvested

The process by which a useful substance is extracted

Home Office

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

Hormone

A chemical messenger produced by a particular gland or cells of the endocrine system. Hormones are transported throughout the body in the blood stream but they produce a response only in specific target cells

Hydrogen bond

An intermolecular 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.

Hyperglycaemic

This is the term used when the blood glucose level is too high (more than 10 mmol/l)

Hypoglycaemic

This is the term used when the blood glucose level is too low (less than 4 mmol/l)

Immune system

The body's own system for protecting it against disease (where it produces antibodies to attack invading pathogens)

In vitro fertilisation

A process where the egg is fertilised outside of the body and then transferred back into the uterus to develop normally

Insulin

A hormone produced by the pancreas. It is active in controlling blood glucose levels as it allows cells in the body to take in and store glucose.

Liver

A large organ in the upper abdomen which manufactures, stores and breaks down substances as required by the body

Mitochondria

Organelles within cells that produce ATP, used as a store of chemical energy. Often called the cell's powerhouse.

Mucosa

The membrane that lines the body's cavities and passages. In certain areas, such as the nose and mouth, this membrane absorbs substances and secretes mucus.

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

Obesity

A disorder where an excessive amount of fat has accumulated in the body. It results when the energy taken in as food is stored in the body instead of being used up through activity

Organelles

A distinct part of the cell, such as the nucleus, ribosome or mitochondrion, which has structure and function.

Pancreas

An endocrine gland which produces insulin

Polysaccharides

Complex carbohydrates consisting of more than one sugar molecule.

Proteins

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.

Receptors

Protein molecules attached to cells that only bind to specific molecules with a particular structure.

Respiration

The biochemical process by which the cells in the body release energy

Messenger RNA (ribonucleic acid)

Single chains of nucleotide units that transmit the information from the DNA inside the cell's nucleus to the ribosomes in the cytoplasm which synthesise the required proteins.

Ribosome

Small organelles that synthesise proteins.

Rough endoplasmic reticulum

A network of membranes within a cell which has ribosomes attached to it. They are important in the synthesis and transportation of proteins.

Stem cells

Undifferentiated cells that can develop into a diverse range of specialised cell types.

Sterile

Uncontaminated by microorganisms

Triglycerides

The most common lipid found in nature and consists of a single glycerol molecule bonded to three fatty acids.

UK Law [for animal testing]

Animal welfare is regulated in the UK by the Animal (Scientific Procedures) Act 1986

Vesicle

A small sac that stores or transports substances inside a cell.

X-ray crystallography

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