KS4 Biology
Biotechnology
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What is biotechnology?
Living things use chemical reactions to produce new
materials.
Biotechnology is the use of these reactions by humans to
manufacture useful products.
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Uses of biotechnology
What products are made using biotechnology?
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Biotechnology – an old art
Can you think of some products that have been made using
biotechnology for thousands of years?
bread
cheese and yoghurt
beer and wine
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Contents
Biotechnology
Introducing biotechnology
Enzymes
Fermentation
Other uses of biotechnology
Summary activities
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What is fermentation?
Yeast cells contain enzymes that converts sugars (such as
glucose and sucrose) into alcohol (ethanol) and carbon
dioxide.
glucose

C6H12O6 (aq) 
ethanol
+
carbon
dioxide
C2H5OH (l)
+
CO2 (g)
This reaction is called fermentation.
Fermentation usually takes place at 20-30°C. It must take
place in anaerobic conditions (without oxygen) otherwise
the ethanol would react with oxygen and turn into vinegar.
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Fermentation in the lab
How can fermentation be shown to create carbon dioxide?
water bath
at 35 °C
sugar solution
and yeast
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limewater
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Uses of fermentation
Fermentation has been used for thousands of years in
brewing and baking.
 Alcoholic drinks such
as beer and wine are
made by adding yeast to
sugary solutions.
 Bread rises due to the
production of bubbles
of carbon dioxide in the
fermenting dough.
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A froth of CO2 and yeast
during fermentation
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Fermentation and wine-making
Grapes convert carbon dioxide
to glucose by photosynthesis.
Grapes are crushed to release their
juice, which contains the glucose.
The juice is fermented under
anaerobic conditions by the
natural yeast on the grape skins.
The enzymes in the yeast convert
the glucose to alcohol.
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Fermentation and beer-making
Barley grains are warmed with water
to germinate. This produces sugar.
Barley is boiled with water
to release the sugar.
Hops are added for flavour.
Yeast is added and enzymes in this
convert the sugar to alcohol.
Beer is usually filtered and the yeast
recycled to make more beer.
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The beer-making process
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Fermentation and bread-making
Flour is mixed with water, yeast, salt
and sugar to make a dough.
The dough is left in a warm
environment to allow fermentation.
Fermentation produces carbon dioxide
gas, which makes the dough rise.
The bread is baked, killing the
yeast and evaporating the alcohol.
Holes are left in the mixture where
the CO2 gas expanded.
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Fermentation
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Contents
Biotechnology
Introducing biotechnology
Enzymes
Fermentation
Other uses of biotechnology
Summary activities
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Making yoghurt
Pasteurized or sterilized milk is
used to kill unwanted bacteria.
The milk is mixed with speciallycultured bacteria and kept warm.
The enzyme lactase from the bacteria
convert milk sugar (lactose) into lactic
acid, which gives a sour taste and
makes the product semi-solid.
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The yoghurt-making process
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