Understanding Biology: Use of biological resources: Edexcel IGCSE Science Single Award Explained

Where biology meets agriculture and industry: the applied science section of the single award

The Pearson Edexcel IGCSE Science Single Award (4SS0) closes its biology content with a section that bridges the laboratory and the real world. Use of biological resources is where you learn how humans harness living organisms to produce food, manufacture medicines and improve crop yields. For a course worth one GCSE that spans biology, chemistry and physics, this section is a reminder that science is not only about understanding nature but also about applying that understanding to practical problems.

These edexcel igcse science single award revision notes cover the two topics within this section: food production and genetic modification. You will find the specification points explained, worked examples where they apply, common pitfalls that cost students marks, and self-check questions. Whether you are using these as standalone edexcel igcse science single award notes or alongside your textbook, the goal is to give you a clear, exam-ready understanding of each concept.

Food production

Glasshouses and polythene tunnels

The specification requires you to describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops. The principle is straightforward: by enclosing plants in a transparent structure, you can control the growing environment in ways that are impossible in an open field.

A glasshouse (or greenhouse) allows light to enter and traps heat inside. This creates a warmer environment than the outside air, which extends the growing season and allows crops to be grown in climates that would otherwise be too cold. Polythene tunnels work on a similar principle but are cheaper and easier to construct, making them accessible to smaller-scale producers across Europe, Africa and Asia.

The specification also requires you to understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses:

Increased carbon dioxide concentration: Carbon dioxide is a raw material for photosynthesis. Up to a point, increasing the concentration of CO₂ inside a glasshouse increases the rate of photosynthesis, which increases the rate at which plants produce glucose and, ultimately, the crop yield. Many commercial growers add CO₂ to their glasshouses using gas burners or bottled gas for this reason.
Increased temperature: Raising the temperature increases the rate of enzyme-controlled reactions inside the plant, including photosynthesis. However, this only works up to an optimum. Beyond a certain temperature, the enzymes begin to denature and the rate falls sharply. The optimal temperature for most crops in glasshouses is between 25 and 30 degrees Celsius.

Exam tip: When explaining why increasing temperature or CO₂ concentration increases crop yield, always link your answer back to photosynthesis. The examiner wants to see the connection: more CO₂ means more raw material for photosynthesis, which means more glucose produced, which means more biomass, which means higher yield. A vague answer like "the plants grow better" does not earn marks.

Yeast in food production

The specification requires you to understand the role of yeast in the production of food, including bread. Yeast is a single-celled fungus that carries out anaerobic respiration (fermentation) when oxygen is limited. The word equation for anaerobic respiration in yeast is:

glucose -> ethanol + carbon dioxide

In bread-making, yeast is mixed into dough. As the yeast ferments the sugars in the flour, it produces carbon dioxide gas. This gas forms bubbles in the dough, causing it to rise. When the bread is baked, the heat kills the yeast and evaporates the small amount of ethanol produced, leaving the characteristic spongy texture.

The specification also asks you to investigate the role of anaerobic respiration by yeast in different conditions. A classic practical involves placing yeast and sugar solution in a flask connected to a delivery tube leading into limewater. As the yeast respires anaerobically, the carbon dioxide produced turns the limewater milky. You can vary the temperature or the concentration of sugar to see how these factors affect the rate of CO₂ production.

Variable changed	Expected result	Explanation
Temperature increased (up to about 40 degrees C)	More bubbles / faster limewater change	Enzymes in yeast work faster at higher temperatures, up to the optimum
Temperature increased beyond 40 degrees C	Fewer bubbles / slower reaction	Enzymes denature; active sites change shape
Sugar concentration increased	More bubbles / faster reaction	More substrate (glucose) available for respiration
No sugar added	Very few or no bubbles	No substrate for the yeast to respire

Genetic modification (genetic engineering)

This is the more conceptually demanding part of the section, and it is where the edexcel igcse science single award biology: use of biological resources content connects directly to modern biotechnology. Genetic modification involves taking a gene from one organism and inserting it into another, giving the recipient organism a new characteristic.

The tools of genetic engineering

The specification requires you to understand two types of enzyme used in genetic engineering:

Restriction enzymes: These cut DNA at specific sequences, known as recognition sites. Different restriction enzymes recognise different sequences, allowing scientists to cut out a specific gene from a donor organism's DNA with precision. The cuts often leave short single-stranded overhangs called "sticky ends," which are important for the next step.
Ligase enzymes: These join pieces of DNA together. Once the desired gene has been cut out of the donor DNA and inserted into a vector, ligase seals the joins, creating a continuous strand of recombinant DNA.

Vectors

The specification requires you to understand how plasmids and viruses can act as vectors. A vector in this context is a carrier that takes a piece of DNA and inserts it into a new cell.

Plasmids are small, circular pieces of DNA found in bacteria. To use a plasmid as a vector, scientists cut it open using the same restriction enzyme that was used to cut out the desired gene. Because both cuts produce matching sticky ends, the gene can be inserted into the open plasmid. Ligase then seals the plasmid, producing recombinant DNA. The plasmid is then reintroduced into a bacterial cell, which now carries the new gene.

Viruses can also act as vectors. They naturally inject their DNA into host cells, so scientists can replace part of the viral DNA with the desired gene. When the modified virus infects a target cell, it delivers the new gene along with its own genetic material.

Manufacturing human insulin

The specification requires you to understand how large amounts of human insulin can be manufactured from genetically modified bacteria. This is a crucial real-world applications of genetic engineering.

The process follows these steps:

The human insulin gene is identified and cut out of human DNA using a restriction enzyme.
A bacterial plasmid is cut open using the same restriction enzyme, producing matching sticky ends.
The human insulin gene is inserted into the open plasmid.
Ligase enzyme seals the gene into the plasmid, creating recombinant DNA.
The recombinant plasmid is inserted into a bacterial cell (such as E. coli).
The genetically modified bacterium is placed in a fermenter with nutrients and allowed to multiply rapidly.
As the bacteria reproduce, they all carry the human insulin gene and produce human insulin as they grow.
The insulin is extracted, purified and used to treat diabetes.

Before genetic engineering, insulin for diabetic patients was extracted from the pancreases of pigs and cattle. This animal insulin was effective but occasionally caused allergic reactions. Genetically engineered human insulin is chemically identical to the insulin produced by a healthy human pancreas, so it carries a much lower risk of adverse reactions and can be produced in essentially unlimited quantities.

Common mistake: Students sometimes write that the gene is inserted "into the bacterium" without mentioning the plasmid. The gene goes into the plasmid first, and then the plasmid goes into the bacterium. The plasmid is the vector. Skipping this step loses marks because it omits the mechanism of transfer.

Genetically modified plants

The specification requires you to understand how genetically modified plants can be used to improve food production. Examples include crops engineered to be resistant to insects (by inserting a gene that produces a natural insecticide), resistant to herbicides (so farmers can spray weed-killer without harming the crop), or able to grow in harsh conditions such as drought or salty soil.

The benefits are higher yields, lower pesticide use, and the ability to grow food in regions where conventional crops would fail. The concerns include the possibility that modified genes could spread to wild plants, the reduction of biodiversity if a single engineered variety dominates agriculture, and the ethical questions around patenting living organisms.

In the exam, you might be asked to discuss the advantages and disadvantages of genetically modified crops. A balanced answer acknowledges both sides and uses specific examples rather than generalities.

The term transgenic

The specification requires you to understand that the term transgenic means the transfer of genetic material from one species to a different species. A bacterium carrying the human insulin gene is transgenic because it contains DNA from a different species (humans). A crop plant carrying a gene from a soil bacterium to make it insect-resistant is also transgenic.

Self-check questions

Try answering each of these from memory before looking back at your notes.

Explain how a glasshouse can increase crop yield, with reference to photosynthesis.
State the word equation for anaerobic respiration in yeast.
Describe the role of carbon dioxide in bread-making.
Explain the difference between a restriction enzyme and a ligase enzyme.
Outline the steps involved in producing human insulin from genetically modified bacteria.
Explain what the term "transgenic" means and give one example.
Give two advantages and two concerns associated with genetically modified crops.
A student investigates the rate of CO₂ production by yeast at 20 degrees C, 35 degrees C and 50 degrees C. Predict the results and explain your prediction.

How this section fits into the wider single award

Biology: use of biological resources edexcel igcse is the final biology section in the 4SS0 specification, and it draws on concepts from earlier topics. Photosynthesis (from the nutrition topic), enzyme function (from biological molecules), and anaerobic respiration (from the respiration topic) all reappear here in applied contexts. If any of those earlier concepts feel shaky, revisiting them will strengthen your understanding of this section as well.

For students taking the igcse 4ss0 biology: use of biological resources exam, the genetic engineering sequence is the part that carries the most detail. Make sure you can describe the full insulin production process in order, name both enzyme types and their functions, and explain the role of the vector. These are the areas where the biology: use of biological resources edexcel igcse questions tend to focus.

Use these edexcel igcse science single award notes as a foundation, then test yourself with edexcel igcse science single award practice questions from past papers. The edexcel igcse science single award explained format works best when you combine reading with active recall: close this page, write out the insulin production steps from memory, and check how many you got right. That cycle of retrieval and correction is what turns revision notes into exam-ready knowledge. The Green Bridge CBT platform supports this approach with topic-specific questions and immediate feedback, helping you identify which areas need further attention before you sit the exam.