iGCSE Biology Section F


Production of beer

Biotechnology - the use of living organisms to make useful chemicals and products

Glucose --> ethanol + carbon dioxide
The carbon dioxide is used to make bread rise.
When yeast respires anaerobically it produces ethanol.

Making beer

  • Barley seeds are germinated. They make amylase to digest starch.
  • Seeds are killed and dried to make malt
  • Malt is ground up and mixed with water in a mash tun. Amylase breaks down starch to maltose
  • Mash is boiled and filtered
  • Hops are added for taste and yeast is added to ferment sugars, making beer
  • Beer is centrifuged, filtered and sometimes pasteurised
  • Beer is put into casks or barrels
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Production of yoghurt

Lactobacillus bacteria is used

  • Milk is pasteurised at 85-95°C for 15-30 minutes.
  • Milk is homogenised
  • Milk is cooled to 40-45°C and inoculated with a starter culture of lactic acid bacteria
  • Mixture is incubated at this temp for several hours while bacteria digest milk proteins and ferment lactose to lactic acid
  • Thickened yoghurt is stirred and cooled to 5°C
  • Flavourings, colorants and fruit may be added before packaging
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Fermenter notes

  • The pH inside is kept constant by adding acid or alkali
  • Filtered air is added when microorganisms need oxygen
  • The fermenter is cooled by water flowing through a water jacket
  • The microorganisms are mixed with the nutrients. This stops them sinking to the bottom and helps keep the temp even throughout the fermenter.
  • Some microorganisms produce acid wastes so the fermenter is made of a metal that will not corrode.
  • The contents of the fermenter are monitored by special probes. These record the conc. of nutrients, temp, pH, oxygen and CO2 levels. The data is fed into a comp which controls the conditions in the fermenter.
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Double helix held together by a series of paired bases
A-T and G-C are always paired
Three bases code for one amino acid
A gene codes for a protein

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Genetic modification

recombinant DNA - the DNA from two different organisms combined
transgenic - an organism that recieves a new gene from a different species
Trangenic organisms will manufacture the protein coded for by its new gene so it will be able to make a new different protein e.g. insulin
restriction enzymes - the enzymes used to cut out the gene from one organism
ligase enzymes - the enzymes used to stick the gene into DNA

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