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KS4 Chemistry. Biotechnology. Contents. Biotechnology. Introducing biotechnology. Enzymes. Fermentation. Other uses of biotechnology. Summary activities. What is biotechnology?. Living things use chemical reactions to produce new materials.

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ks4 chemistry

KS4 Chemistry




Introducing biotechnology



Other uses of biotechnology

Summary activities

what is biotechnology
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.

Biotechnology is also about genetically modifying living things to produce medicines, and to introduce useful characteristics into plants and animals.

uses of biotechnology
Uses of biotechnology

What products are made using biotechnology?

biotechnology an old art


cheese and yoghurt

beer and wine

Biotechnology – an old art

Can you think of some products that have been made using biotechnology for thousands of years?

biotechnology a new science

using enzymes to improve detergents

transferring disease-resistance genes into plants

manufacturing medicines such as penicillin

Biotechnology – a new science

Can you think of more recent uses of biotechnology?



Introducing biotechnology



Other uses of biotechnology

Summary activities

enzymes the key to it all
Enzymes – the key to it all

Almost all chemical reactions that take place inside living things are controlled by enzymes.

Enzymes are biological catalysts. They speed up chemical reactions without being used up.

Every cell in every plant and animal contains many different types of enzyme. Each enzyme catalyzes a different reaction.

model of an enzyme
Model of an enzyme

Enzymes are very large and complex molecules made of protein.

This is a computer-generated model of an enzyme molecule. The small particle on the left is the reactant molecule.

enzymes the lock and key model


Enzymes – the ‘lock and key’ model

Enzymes are very specific about what reaction they catalyse. Only molecules with exactly the right shape will bind to the enzyme and react. These are called reactant molecules, or the substrate.

The part of the enzyme with which the reactant binds is called the active site.This is a very specific shape.

The reactant is said to fit like a ‘key’ in the ‘lock’ of the enzyme’s active site. This way of describing how an enzyme works is called the ‘lock and key’ model.

enzymes and temperature
Enzymes and temperature

Enzyme-catalyzed reactions take place across a range of temperatures, usually 20-45°C.

All enzymes work best at only one particular temperature, called the optimum temperature. Different enzymes have different optimum temperatures.

As the temperature decreases below the optimum, the reaction slows down and the enzyme will eventually become inactive. The reaction will stop.

As the temperature increases above the optimum, the reaction quickly slows down and stops completely. This is because the temperature irreversibly alters the shape of the enzyme and stops it working.

At this point, the enzyme is said to be denatured.

enzymes and ph
Enzymes and pH

Enzyme reactions occur across a range of pH values.

Like for temperature, each enzyme will work best at only one particular pH.

Some enzymes, for example, those in the stomach, work best in acidic conditions. Other enzymes work best in alkaline conditions.

If the pH value changes sufficiently, the enzyme’s shape irreversibly changes and it will be denatured.



Introducing biotechnology



Other uses of biotechnology

Summary activities

what is fermentation







C2H5OH (l)

CO2 (g)

What is fermentation?

Yeast cells contain enzymes that converts sugars (such as glucose and sucrose) into alcohol (ethanol) and carbon dioxide.

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.

fermentation in the lab

water bath at 35°C

sugar solution and yeast


Fermentation in the lab

How can fermentation be shown to create carbon dioxide?

uses of fermentation

A froth of CO2 and yeast during fermentation

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.
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.

Fermentation and wine-making
fermentation and beer making
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.

fermentation and bread making
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.



Introducing biotechnology



Other uses of biotechnology

Summary activities

making yoghurt
Making yoghurt

Pasteurized or sterilized milk is used to kill unwanted bacteria.

The milk is mixed with specially-cultured 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.

making cheese
Making cheese

Like yoghurt, cheese is made from cow’s milk. Goat or sheep’s milk can also be used.

Specially-cultured bacteria are added to sour the milk.

A type of enzyme called a coagulant, such as rennet, is added. This forms solid curds and liquid whey.

Whey, mainly water and lactose, is removed. The curd is salted, moulded and pressed to become cheese.

biological washing powder
Biological washing powder

Biological washing powders contain enzymes to help remove stains.

  • Proteases break down proteins in stains such as grass, blood and sweat.
  • Lipases break down stains containing fat and oil.

wax coat

  • Carbohydrases break down stains containing carbohydrates, such as starch.


The enzymes are coated with a special wax. This melts in the wash, releasing the enzymes. Once the stains have been broken down, they are easier to remove by the detergent.

sugar syrup
Sugar syrup

A type of enzyme called isomerase converts the sugar glucose into fructose, another type of sugar.

Fructose is sweeter than glucose, so a smaller amount is needed. This makes fructose syrup a useful ingredient in slimming foods.

Invertase is used to create soft-centered chocolates. The centre initially contains sucrose (cane sugar) and is hard. The invertase breaks down the sucrose into the simpler sugars glucose and sucrose, making the centre soft and runny.

Another type of enzyme called carbohydrase converts starch syrup (e.g. from potatoes) into sugar syrup, for use in sweets, soft drinks and baking.

enzymes and industry
Enzymes and industry

Enzymes are becoming more common as catalysts for industrial processes. Why is this the case?

  • Enzymes work at fairly low temperatures – this saves energy and money, and reduces pollution.
  • Enzymes work in fairly mild conditions (normal pressure, in water and pH close to 7) – this reduces the need for potentially dangerous chemicals.
  • Enzyme-reactions can be easily controlled – by slightly changing the temperature or pH.
  • Enzymes are biodegradable – they reduce pollution and environmental problems.
general enzyme reactions
General enzyme reactions

What are the steps in the production of an enzyme-catalyzed reaction?

1. Find or bioengineer microbes (e.g. bacteria, yeast) that produce the required enzymes.

2. Make a solution containing the nutrients the microbes need to grow, and the reactant.

3. Add a small amount of the microbe to the solution. Keep warm, correct the pH and provide oxygen if necessary.

4. The enzyme will catalyse the reaction, converting reactant into product.

5. Separate the product.

continuous enzymes reactions
Continuous enzymes reactions








stainless steel reactor


Large-scale enzyme reactions require a continuous, rather than a batch, process.

Reactants are constantly being fed in and products are constantly being removed.



Introducing biotechnology



Other uses of biotechnology

Summary activities

  • active site – The part of the enzyme into which the reactant molecule fits.
  • catalyst – A substance that changes the rate of a reaction without being used up.
  • denatured – The state of an enzyme when it has been irreversibly damaged and has changed shape.
  • enzyme – A biological catalyst.
  • fermentation – The conversion of sugar to ethanol and carbon dioxide by enzymes in yeast.
  • lock and key – A model of how enzymes work and the importance of their shape.