Inside Living Cells B2

Revision cards for B2, Inside Living Cells part of the edexcel additional science GCSE.

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Fermentation is the process of using micro - organisms to break down nutrients into useful products.

Different products that we can make via fermentation are:

  • Alcohol,wine,cider
  • Soya sauce, marmite, vinegar
  • Quorn
  • Cheese, bread
  • Activia, yoghurt
  • Antiobiotics such as penicillin


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Micro - organisms

A microbe is a living organism that is so small that it can only be seen through a microscope.

  • Scientists can grow these cells in a culture medium. There must be sugar in the culture medium.
  • You should control the temperature, it has to be at room temperature.
  • You need to provide lots of nutrients for the sugar.
  • They have a water jacket to keep it cool.
  • You have to monitor the pH.
  • Insulin is produced by bacteria.

Micro - organisms are very useful because they can grow and reproduce quickly, they are easy to handle, can operate indoors and can make use of waste products from other processes.



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A fermenter

A fermenter is a controlled environment ( i.e. a large device) that provides optimum conditions for micro - organisms to grow and feed.

The optimum conditions for growth are conditions in which micro - organisms grow best. The optimum conditions include a certain mixture of several things including nutrients, an optimum temperature and an optimum pH. All of these conditions inside the fermenter have to be carefully controlled to ensure that there is a maxiumum yield. The maxiumum yield means that the micro - organisms produce as much of the product of possible.

The contents of the fermenter are monitered by special probes, these record the concentration of the nutrients, the temperature, pH, oxygen and carbon dioxide levels. This data that is collected is then fed into a computer. The computer then automatically controls all the conditions inside the fermenter. 

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The different parts of a fermenter and their job

Water jacket - the fermenter is cooled by water flowing through a water jacket.

Stirring paddles - the micro - organisms are mixed with the nutrients. This stops them sinking to the bottom, and helps keep the temperature even throughout the fermenter.

Air inlet - Filtered air is added when micro - organisms need oxygen.

Temperature and pH probes - The pH inside is kept constant by adding acid or alkali.

Fermenter case - Some micro - organisms produce acid wastes, so the fermenter is made of a metal that won't corrode, like stainless steel.


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Aseptic precautions

However before the fermenter is filled with all the necessary nutrients and culture there are certain measures that have to be taken to avoid any contamination from unwanted organisms. These measures are called aseptic precautions. To ensure these measures are carried through scientists check the following things:

The pipes and the inside of the tank is cleaned and sterilised.If this is not done then bacteria or fungi might get into the fermenter and contaminate the product. Or the contaminating micro  - organisms will reduce the yield of the product because the have competed with the organism that is in the culture.


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Yeast is an example of a micro - organism ( contains enzymes). It is used to help a process called fermentation.

Sugar = Alcohol + Carbon Dioxide

The alcohol from this process is used in making drinks and the carbon dioxide can be used to make bread rise.                                                                        

The micro - organism yeast is used to:

  • Make wine
  • Make the bacteria in milk
  • Used to make lactic acid for yoghurt


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Advantages of using micro - organisms for food pro

There are many advantages that micro - organisms create when it comes to food production and they are as follows:

  • They just need something to grow them in, food, oxygen and the right temperature.
  • The food can be produced whether the climate is hot or cold.
  • Micro - organisms can use waste products from agriculture and industry for their life processes. For example the mould that makes Quorn originates from the waste that is produced from flour making.
  • Micro - organisms like bacteria and fungi can grow very quickly.
  • Means micro - organisms are cheaper than other methods.
  • They are easy to manipulate in a fermenter 
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Fermentation in depth

As micro - organisms grow they use up the nutrients that are found in the culture medium ( the liquid in which micro - organisms are cultivated), they then produce substances and waste products. This process is called fermentation.

We already know that one of the main uses for fermentation is for the production of beer and wine from the micro - organism yeast. This yeast is given sugar and uses it as a nutrient so that it can get a supply of energy from it. This sugar is then broken down into two waste products, which are: alcohol and carbon dioxide. When making something like wine or beer the product that we want is the alcohol - the chemical name for it being ethanol - however we know that fermentation by micro - organisms can also be used to produce other products, however these micro - organisms would have to be cultivated in a fermenter.

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Explain how DNA can be transferred into micro - or

Micro - organisms and bacteria both contain DNA. Both of these living things use the same genetic code as us humans and several other organisms. By changing this DNA scientists can produce new products.

1. First they identify the protein that is needed for example they might need a cure for diabetes so they get the protein for insulin.

2. They then cut out the bit of the human DNA that is used to create insulin in the body.

3. This piece of DNA which they have removed is then inserted into the bacteria.

4. This bacteria now contains the gene for producing insulin.

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Explain how DNA can be transferred into micro - or

If the bacteria is then cultivated inside a fermenter then you can reproduce large quantities of the bacteria, or in this case insulin. In the past before this method was discovered the insulin had to found and extracted out of animal's organs. Using the process of fermentation has helped a lot in this prospect.

There are also many other things made in this way such as the human growth hormone and enzymes.

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Alice Deane


Please leave me any comments for improvement or any important details that I have left out.




This was really useful and really well sumarised but you missed out respiration topic which is included in this unit.

Thanks though it's really useful for my revision☺

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