Biotechnology in Medicine
1. Production of Insulin
Learning outcomes
- I can explain why insulin is important in the treatment of diabetes.
- I can describe how recombinant DNA technology is used to produce insulin.
- I can compare modern insulin production with historical methods.
- I can explain the role of genetically engineered bacteria in insulin production.
- I can evaluate the benefits of biotechnology in medicine.
Insulin is one of the best-known examples of biotechnology being used to improve medicine.
For much of the 20th century, insulin used to treat diabetes was extracted and purified from the pancreases of pigs and cattle. Today, insulin and many insulin analogues can instead be produced using genetically engineered microorganisms.
This is possible because scientists can place genetic instructions for producing insulin into microorganisms and use those cells as tiny biological factories.
The development of recombinant human insulin was also historically important: in 1982, recombinant human insulin became the first recombinant-DNA-derived medicine approved for human use in the United States.
What Is Insulin?
Insulin is a protein hormone produced by beta cells in the pancreas.
The pancreas is an organ located behind the stomach.
Insulin plays an important role in controlling the concentration of glucose in the blood.
After a carbohydrate-containing meal:
food digested → glucose absorbed → blood glucose rises
The pancreas responds by releasing insulin.
Insulin helps body cells take up and use glucose and encourages storage of excess glucose, particularly as glycogen.
As a result:
blood glucose concentration decreases toward its normal range.
Why Do We Need Glucose?
Glucose is an important energy source for cells.
During cellular respiration, cells can use glucose to release energy:
glucose + oxygen → carbon dioxide + water
The released energy can support processes such as:
- muscle contraction
- active transport
- protein synthesis
- cell division
- maintaining body temperature
- nerve function
The body therefore needs glucose—but its concentration in the blood must be regulated.
How Insulin Controls Blood Glucose
When blood glucose rises, insulin helps coordinate several responses.
Body Cells
Insulin signals many cells to increase glucose uptake.
Liver
Insulin promotes the conversion of glucose into glycogen for storage.
Muscles
Muscle cells can take up glucose and store some as glycogen.
Fat Tissue
Insulin also influences the storage and use of nutrients.
A simplified negative-feedback pathway is:
blood glucose rises
↓
pancreatic beta cells release insulin
↓
glucose uptake and storage increase
↓
blood glucose falls
↓
insulin secretion decreases
This is an example of homeostasis.
Diabetes
Diabetes mellitus is a group of conditions involving problems with blood-glucose regulation.
Two major forms are Type 1 diabetes and Type 2 diabetes.
They are not the same condition.
Type 1 Diabetes
In Type 1 diabetes, the immune system destroys the insulin-producing beta cells of the pancreas.
As a result, the body produces little or no insulin.
Without sufficient insulin:
- blood glucose can become dangerously high
- cells cannot regulate glucose use normally
- serious short-term and long-term complications can develop
People with Type 1 diabetes therefore require insulin treatment.
Type 2 Diabetes
In Type 2 diabetes, body tissues become less responsive to insulin, a condition called insulin resistance.
Over time, insulin production may also become insufficient.
Treatment varies and can include:
- dietary and lifestyle changes
- oral medicines
- other injectable medicines
- insulin
Some people with Type 2 diabetes therefore also use insulin.
Why Insulin Treatment Is Important
For someone who cannot produce enough effective insulin, insulin treatment helps regulate blood glucose.
Without appropriate treatment, prolonged high blood glucose can damage tissues and organs.
Complications can involve:
- blood vessels
- nerves
- kidneys
- eyes
- heart
Very severe insulin deficiency can also produce dangerous acute metabolic problems.
Insulin therapy therefore replaces or supplements an essential biological signal that the body cannot provide adequately.
Insulin Is a Protein
Insulin is a relatively small protein composed of amino acids.
Mature human insulin contains two polypeptide chains:
- A chain
- B chain
These are connected by disulfide bonds.
The amino-acid sequence determines how insulin folds and interacts with insulin receptors.
Therefore, producing insulin requires the correct genetic information for its amino-acid sequence.
Before Genetic Engineering
Insulin treatment began long before recombinant DNA technology existed.
Historically, pharmaceutical insulin was extracted primarily from the pancreases of:
- pigs
- cattle
These organs were obtained largely as by-products of the meat industry.
The insulin then had to be:
- extracted
- purified
- processed
- standardized
Animal insulin saved countless lives and transformed diabetes from a frequently fatal disease into a treatable condition.
Animal Insulin and Human Insulin
Pig and cattle insulin are similar to human insulin, but their amino-acid sequences are not identical.
Pig insulin is especially similar to human insulin.
Animal-derived insulin was effective, but there were disadvantages compared with modern recombinant production.
These included:
- dependence on animal tissue
- complex purification
- variation between animal and human insulin
- unwanted immune reactions in some patients
- limitations in scaling and standardization
However, historical animal insulin was an extraordinarily important medical treatment.
A Major Biotechnology Breakthrough
During the development of recombinant DNA technology in the 1970s, scientists learned how to combine DNA from different sources and introduce engineered genetic material into microorganisms.
This created a remarkable possibility:
Instead of extracting insulin from animal organs, could microorganisms be genetically programmed to manufacture human insulin?
The answer was yes.
This became one of the first major commercial successes of genetic engineering.
Recombinant DNA Technology
Recombinant DNA is DNA constructed by joining genetic material using biotechnology.
A simplified insulin-production pathway is:
human insulin genetic information
↓
DNA prepared for microbial expression
↓
DNA placed into a suitable vector
↓
vector introduced into microorganisms
↓
engineered cells reproduce
↓
insulin-related protein produced
↓
product recovered and processed
↓
purified insulin
Step 1: Obtain the Genetic Information
Scientists need genetic instructions that encode the desired insulin product.
Modern production methods can use DNA sequences designed or synthesized for efficient expression in the chosen host organism.
An important complication is that human genes can contain introns, while bacteria do not process RNA in the same way human cells do.
Therefore, biotechnology uses an appropriate coding sequence rather than simply transferring an untouched human chromosomal gene into bacteria.
At school level, the important idea is:
Scientists obtain the genetic instructions needed to make the insulin protein.
Step 2: Use a Vector
A vector carries genetic material into a host cell.
In bacteria, engineered plasmids can be used as vectors.
A plasmid is a small, usually circular DNA molecule separate from the bacterial chromosome.
The engineered DNA must include more than simply the protein-coding sequence.
Suitable regulatory sequences are also needed so the microorganism can express the genetic information.
Step 3: Construct Recombinant DNA
In classic recombinant DNA diagrams, a plasmid is opened and the desired DNA is inserted.
Two enzyme types are commonly introduced in school biology:
Restriction Enzymes
Cut DNA at particular recognition sequences.
DNA Ligase
Joins DNA fragments together.
A simplified model is:
plasmid + insulin DNA
↓
DNA cut/prepared
↓
DNA fragments joined
↓
recombinant plasmid
Modern industrial methods can use more advanced DNA assembly techniques, but the plasmid model remains useful for understanding recombinant DNA.
Step 4: Introduce DNA into Bacteria
The recombinant DNA is introduced into suitable bacterial cells.
The uptake of external DNA by bacteria is called transformation.
Not every cell necessarily receives the engineered DNA.
Scientists therefore need ways to identify cells containing the desired genetic construct.
Those cells can then be selected for further growth.
Step 5: Grow the Engineered Bacteria
Once suitable engineered bacteria have been obtained, they can be grown in large quantities.
Bacteria reproduce rapidly by binary fission.
One engineered cell can therefore produce a population of many genetically similar cells.
These cells contain the genetic instructions needed for production.
The bacteria become biological manufacturing systems.
Fermentation and Bioreactors
Large-scale production occurs under carefully controlled conditions.
Engineered microorganisms can be grown in large vessels called bioreactors or fermenters.
Engineers and scientists control conditions such as:
- temperature
- pH
- nutrients
- oxygen supply
- mixing
- contamination
These conditions help maintain healthy cells and efficient production.
Why Control Temperature?
Enzymes control the chemical reactions occurring inside cells.
If temperature becomes too low:
metabolic reactions may become slower
If temperature becomes too high:
proteins can lose function and cells may be damaged
The bioreactor must therefore maintain a suitable temperature.
Why Control pH?
Proteins and enzymes function best within particular pH ranges.
Large changes in pH can alter protein structure and cell metabolism.
Sensors can therefore monitor pH.
If necessary, control systems can adjust the conditions.
Why Supply Oxygen?
Some production organisms require oxygen for efficient aerobic respiration.
Aerobic respiration releases energy needed for:
- growth
- cell division
- protein synthesis
Air or oxygen may therefore be supplied to the bioreactor, depending on the organism and production process.
Why Stir the Culture?
Mixing helps distribute:
- nutrients
- oxygen
- cells
- thermal energy
throughout the bioreactor.
Without sufficient mixing, conditions may differ greatly between different regions of the vessel.
However, excessive mixing can also create problems, so industrial conditions are optimized carefully.
Step 6: Protein Production
Inside the engineered cells, genetic information is expressed.
A simplified pathway is:
DNA → mRNA → protein
This involves:
Transcription
Information in DNA is copied into RNA.
Translation
Ribosomes use the RNA information to assemble amino acids into a polypeptide.
The engineered microorganism therefore uses its own cellular machinery to manufacture the desired protein.
Step 7: Recover the Product
Producing the protein is not the end of the process.
The desired product must be recovered from the production system.
Depending on the manufacturing method, this may involve separating:
- cells
- culture liquid
- unwanted proteins
- other cellular materials
The insulin product must then undergo appropriate processing.
Step 8: Purification
Medical insulin must be highly purified.
Purification can involve techniques such as chromatography, which separates substances according to their physical or chemical properties.
The final product must meet strict standards for:
- identity
- purity
- concentration
- biological activity
- sterility and microbiological quality
- consistency
This is crucial because the insulin will be used as a medicine.
The Bacteria Are Not the Medicine
This is an important distinction.
The genetically engineered bacteria are used to produce the insulin.
The patient does not receive the production bacteria.
Instead:
engineered bacteria → produce protein → insulin recovered → insulin purified → medicine prepared
The final insulin medicine is carefully manufactured and tested.
Why Doesn't Injected Insulin Contain Bacterial DNA?
During manufacturing, the desired insulin is separated and purified from the production system.
Quality-control procedures ensure that the final medicine meets strict specifications.
Therefore, the purpose of the engineered microorganism is to act as a production organism, not to become part of the final treatment.
Why Is Insulin Usually Injected?
Insulin is a protein.
If ordinary insulin were swallowed, digestive enzymes and stomach conditions would break much of it down just as they break down proteins in food.
Insulin therefore needs delivery methods that allow it to reach the body in an active form.
Common methods include:
- insulin pens
- syringes
- insulin pumps
Modern Insulin Analogues
Biotechnology can do more than simply reproduce the natural human insulin sequence.
Scientists can alter parts of the insulin molecule to change how quickly or slowly it acts.
These modified forms are called insulin analogues.
Some are designed to act:
- rapidly
while others are designed to act:
- over longer periods
This allows treatment to be adjusted to different needs.
Genetic engineering therefore allows scientists not only to copy a biological molecule, but sometimes to modify it for particular therapeutic purposes.
Historical vs Modern Insulin Production
| Historical Animal-Based Production | Recombinant Production |
|---|---|
| Insulin obtained from animal pancreases | Insulin produced using engineered cells |
| Mainly pigs and cattle | Microorganisms such as bacteria or yeast |
| Dependent on animal tissues | Based on controlled cell culture |
| Animal insulin differs slightly from human insulin | Can produce human insulin or designed analogues |
| Extensive extraction and purification required | Controlled biological production followed by purification |
| Historically life-saving | Supports modern large-scale manufacturing |
Both methods require careful purification and quality control.
Advantages of Recombinant Insulin
Modern biotechnology provides several important advantages.
Human Insulin Sequence
Recombinant systems can produce insulin corresponding to the human protein.
Consistency
Controlled manufacturing can produce highly standardized batches.
Scalability
Microorganisms can be cultured in large bioreactors.
Reduced Dependence on Animal Tissue
Large quantities of animal pancreases are no longer necessary for recombinant production.
Insulin Analogues
Genetic engineering allows scientists to design forms with altered action profiles.
Manufacturing Control
Production conditions can be carefully monitored.
Does Recombinant Insulin Mean Unlimited Insulin?
No.
Biotechnology makes large-scale production possible, but manufacturing still requires:
- specialized facilities
- trained workers
- raw materials
- purification
- quality control
- sterile processing
- packaging
- storage
- distribution
Scientific ability to produce a medicine does not automatically guarantee that every patient can obtain it easily or affordably.
This is an important distinction when evaluating biotechnology's impact on society.
Biotechnology and Medicine
Insulin demonstrates a broader principle.
If scientists can identify useful genetic information, suitable cells may sometimes be engineered to manufacture the corresponding biological product.
Similar biotechnology approaches are used to produce some:
- hormones
- enzymes
- clotting factors
- antibodies
- vaccine components
Insulin production helped demonstrate that recombinant DNA technology could become a practical medical technology.
From Laboratory Discovery to Medicine
Developing recombinant insulin required knowledge from many scientific fields.
Genetics
Understanding DNA and genes.
Molecular Biology
Understanding gene expression.
Microbiology
Growing microorganisms.
Biochemistry
Understanding proteins.
Chemical Engineering
Designing large-scale bioreactors and purification systems.
Medicine
Understanding diabetes and insulin treatment.
This makes recombinant insulin an excellent example of how different scientific disciplines can work together.
Worked Example 1: Sequence the Process
Place these stages in the correct order:
A. Insulin is purified.
B. Engineered bacteria are grown.
C. Suitable insulin genetic information is placed into a vector.
D. The engineered DNA is introduced into bacterial cells.
E. The cells produce the desired protein.
Correct Order
C → D → B → E → A
So the overall sequence is:
genetic engineering → cell growth → protein production → purification
Worked Example 2: Why Use Bacteria?
A biotechnology company needs to produce a large amount of a therapeutic protein.
Why might microorganisms be useful?
Answer
Microorganisms can:
- reproduce rapidly
- be grown in large populations
- be genetically engineered
- express useful proteins
- grow under controlled conditions in bioreactors
A large population can therefore produce significant quantities of a desired biological product.
Worked Example 3: Bioreactor Growth
Suppose an engineered bacterial population doubles every 40 minutes under simplified ideal conditions.
It begins with:
1 million cells
After 40 minutes:
2 million
After 80 minutes:
4 million
After 120 minutes:
8 million
After 160 minutes:
16 million
This demonstrates why rapidly reproducing microorganisms can be useful in biotechnology.
Real industrial cultures are more complicated and do not continue doubling indefinitely.
Worked Example 4: Comparing Methods
A student says:
"Animal insulin worked, so recombinant insulin provided no real advantage."
Evaluate the statement.
Answer
Animal insulin was extremely important and saved many lives.
However, recombinant technology provided additional advantages, including:
- production of human insulin
- reduced dependence on animal tissues
- highly controlled large-scale production
- ability to engineer insulin analogues
- consistent manufacturing systems
Therefore, the historical method was valuable, while recombinant technology provided important additional capabilities.
Benefits of Biotechnology in Medicine
The production of insulin illustrates several major benefits.
Reliable Biological Production
Cells can manufacture complex molecules that may be difficult to produce by simple chemical synthesis.
Large-Scale Production
Bioreactors allow large populations of production cells to be cultured.
Precision
Specific genetic sequences can be used to produce particular proteins.
Innovation
Proteins can sometimes be modified to improve medical usefulness.
Reduced Dependence on Animal Sources
Some medicines no longer require extraction from animal tissues.
Wider Applications
The same principles can be adapted to produce many different therapeutic proteins.
Limitations and Challenges
Biotechnology is powerful, but it is not effortless.
Challenges include:
- expensive production facilities
- risk of contamination
- complex purification
- strict regulatory requirements
- storage and distribution requirements
- maintaining product consistency
- ensuring accessibility and affordability
Genetic engineering solves the problem of how cells can produce the desired protein, but many additional steps are required before that protein becomes a safe medicine.
Common Mistakes
Mistake 1: "Bacteria naturally produce human insulin."
They do not.
Production organisms are genetically engineered with suitable genetic information.
Mistake 2: "Patients are injected with genetically modified bacteria."
No.
The bacteria are production organisms.
The insulin is recovered and purified before being formulated as medicine.
Mistake 3: "The insulin gene simply replaces the bacterial chromosome."
Typically, engineered genetic constructs can be introduced using vectors such as plasmids.
The basic school model does not involve replacing the entire bacterial chromosome.
Mistake 4: "Restriction enzymes join DNA."
Restriction enzymes cut DNA at particular sequences.
DNA ligase joins DNA fragments in classic recombinant-DNA methods.
Mistake 5: "A plasmid is a bacterium."
A plasmid is a small DNA molecule that can exist inside a bacterial cell.
Mistake 6: "Once bacteria produce insulin, it can immediately be injected."
No.
The product must be:
- recovered
- processed
- purified
- tested
- formulated
before medical use.
Mistake 7: "Insulin cures diabetes."
Insulin is an essential treatment for Type 1 diabetes and is used by some people with other forms of diabetes, but it does not generally eliminate the underlying condition.
Mistake 8: "All people with diabetes produce no insulin."
This is incorrect.
Type 1 and Type 2 diabetes involve different biological problems.
Mistake 9: "Modern insulin production does not require purification."
It does.
Purification and quality control remain essential parts of pharmaceutical manufacturing.
Mistake 10: "Recombinant insulin was useful only because it was cheaper."
Its importance is broader than cost alone.
Benefits include controlled production, human insulin sequences, reduced dependence on animal tissues, consistency, scalability, and the development of insulin analogues.
Check Your Understanding
1. Insulin
What is insulin?
Identify:
- where it is normally produced
- what type of molecule it is
- its role in blood-glucose regulation
2. Diabetes
Explain why a person with Type 1 diabetes requires insulin treatment.
3. Historical Production
Describe how insulin was obtained before recombinant DNA technology became widely used.
Identify one advantage and one limitation of the historical method.
4. Recombinant DNA
Put these into a logical sequence:
- engineered bacteria reproduce
- insulin is purified
- genetic information is placed into a vector
- protein is produced
- DNA is introduced into bacteria
5. Plasmids
What is a plasmid?
Explain why plasmids can be useful in genetic engineering.
6. Bacteria
Explain why bacteria can act as biological factories for producing useful proteins.
7. Bioreactors
Identify four conditions that may need to be controlled inside a bioreactor.
Explain why controlling one of them is important.
8. Compare
Give three differences between historical animal-based insulin production and modern recombinant production.
9. Evaluate
Identify three benefits and two challenges associated with using biotechnology to manufacture medicines.
10. Challenge
A student says:
"Scientists put the human insulin gene into bacteria, grow them, and inject the bacteria into patients."
Explain everything that is incorrect or incomplete about this statement.
Your answer should include:
- genetic information
- vector
- engineered microorganism
- bioreactor
- gene expression
- protein production
- purification
- quality control
Key Terms
- Insulin – protein hormone involved in regulating blood glucose
- Pancreas – organ containing insulin-producing beta cells
- Beta cell – pancreatic cell that produces insulin
- Diabetes mellitus – group of conditions involving impaired blood-glucose regulation
- Type 1 diabetes – autoimmune condition involving destruction of insulin-producing beta cells
- Type 2 diabetes – condition involving insulin resistance and often impaired insulin production
- Homeostasis – regulation of internal conditions within suitable limits
- Recombinant DNA – DNA constructed by combining genetic material using biotechnology
- Genetic engineering – deliberate manipulation of genetic material
- Plasmid – small DNA molecule commonly found in bacteria and usable as a genetic vector
- Vector – carrier used to introduce genetic material into cells
- Restriction enzyme – enzyme that recognizes particular DNA sequences and cuts DNA
- DNA ligase – enzyme that joins DNA fragments
- Transformation – uptake of external genetic material by a bacterial cell
- Gene expression – use of genetic information to produce a functional product
- Bioreactor – controlled vessel used to grow cells or microorganisms
- Fermentation – controlled cultivation of microorganisms or cells for production
- Purification – separation of the desired product from unwanted substances
- Chromatography – technique used to separate substances
- Recombinant human insulin – human insulin manufactured using recombinant biotechnology
- Insulin analogue – modified insulin designed to have particular properties or action profiles
- Biopharmaceutical – medical product produced using biological systems
Key Takeaways
- Insulin is a protein hormone produced by beta cells in the pancreas.
- Insulin plays an essential role in regulating blood glucose concentration.
- People with Type 1 diabetes require insulin because their insulin-producing beta cells have been destroyed by an autoimmune process.
- Historically, medical insulin was mainly extracted from pig and cattle pancreases.
- Animal insulin was a life-saving treatment but differs somewhat from human insulin and depends on animal tissue.
- Recombinant DNA technology allows microorganisms to be genetically engineered to produce insulin-related proteins.
- Plasmids can act as vectors that carry engineered genetic information into bacteria.
- Engineered microorganisms can be grown in large bioreactors under controlled conditions.
- The microorganisms use their cellular machinery to express the engineered genetic information and manufacture the desired protein.
- Producing the protein is only part of the process: insulin must also be recovered, purified, tested, and formulated.
- Patients receive the purified medicine—not the genetically engineered production bacteria.
- Recombinant biotechnology reduces dependence on animal tissue and supports controlled, large-scale production of human insulin.
- Genetic engineering also allows the development of insulin analogues with different action profiles.
- The same general biotechnology principles are used to manufacture many other therapeutic proteins.
- Recombinant insulin is therefore an important example of how understanding DNA, microorganisms, proteins, engineering, and medicine can be combined to solve a major human health problem.