Some microorganisms help us. To explain an application, name the organism, say what it does, and state the useful result.
This lesson is part of microorganisms. It builds on interpreting growth-condition data, because each process works best in set conditions.
What are the main beneficial uses?
Each row below follows the chain: organism, process, result.
| Application | Microorganism | Process | Result |
|---|---|---|---|
| Bread | Yeast | Respires sugar, releases carbon dioxide | Dough rises |
| Yoghurt | Lactobacillus bacteria | Changes milk sugar to lactic acid | Milk thickens and turns sour |
| Antibiotics | Some fungi and bacteria | Make chemicals that stop bacteria growing | Used in treating bacterial infection |
| Compost | Bacteria and fungi | Decompose dead plant matter | Nutrients return to the soil |
Worked example: bread making
Question: Explain why dough rises when yeast is added.
Step 1: name the organism and the food. Yeast uses the sugar in the dough as food.
Step 2: state the process. Yeast respires, which breaks down sugar and releases carbon dioxide gas.
Step 3: state the result. The gas is trapped in the dough as bubbles. The bubbles expand, so the dough rises and becomes soft and light.
A warm place helps because yeast grows faster at a warm temperature. Very high heat kills the yeast and the dough stops rising.
Why the chain matters
A chain answer earns marks at each link. If you write only “yeast makes bread rise”, you earn one mark at most.
The same three steps explain other uses. In yoghurt, bacteria are the organism, the lactic acid is the product, and thickening is the result.
The mistake that costs marks
The slip is to state the use but skip the process. “Bacteria make yoghurt” is true, but it does not say how.
| Wrong | Right |
|---|---|
| Yeast makes bread | Yeast respires sugar and releases carbon dioxide, so dough rises |
| Fungi give medicine | Some fungi make chemicals that stop bacterial growth |
| Bacteria clean the soil | Decomposers break down dead matter and return nutrients to the soil |
Another slip is to say that a microorganism “eats” something and stop there. Add what forms as a result of that process.
Check yourself
A baker says that dough rises faster in a warm kitchen than in a fridge. Use your knowledge of growth conditions and yeast to explain why.
Answer
Yeast respires faster at a warm temperature, so it releases carbon dioxide more quickly.
In the fridge the reactions are slower, so less gas forms and the dough rises slowly.
What to study next
Not every microorganism is useful, and questions often turn to infection next. Continue with distinguishing infection concepts from personal medical advice, then use the practice set.
To practise explaining processes with a teacher, see online one-to-one Science tuition.