1. REACTIONS INVOLVING ENZYMES:
KS4
REACTIONS INVOLVING ENZYMES:
BIOTECHNOLOGY

2. What is biotechnology?
Living things use chemical reactions to produce new materials.
They often do this under very much “gentler” conditions than are possible in conventional chemical reactions because they use biological catalysts called enzymes.
Biotechnology is about how we can use either the living materials themselves or the enzymes extracted from them to manufacture chemicals.
Increasingly, it is also about genetically modifying living things so that they can manufacture chemicals useful to them or us.

3. Biotechnology – an old art
Biotechnology is not new: it has been used for thousands of years.
Some examples of such process include:
Bread making
Wine and beer making
Yogurt making

4. Biotechnology – a new science
Other aspects of biotechnology are much more recent.
These include include:
Using enzymes to improve detergents
Manufacturing antibiotics like penicillin
petri dish with penicillin
Transferring disease resistant genes into plants

5. Enzymes – the key to it all
Almost all chemical reactions that take place inside living things are controlled by enzymes.
Enzymes are large molecules found in living things that act as biological catalysts.
Catalysts are chemicals that speed up reactions without getting used up.
Enzymes are
not living –
they are just
molecules
Research has shown that the shape of enzymes is the key to their catalysis.

6. Enzymes – lock and key
Enzymes are very specific about the reactions they catalyse. They absorb molecules that fit into an active site where reaction becomes more likely.
They are often said to fit like a lock and key.
enzyme
reactant
active
site
Adsorption into active site
Reaction
products
Desorption of products

7. Enzymes and temperature
Most enzyme reactions occur best at temperature of about 20-40oC.
This is not surprising as this is the temperature that they will have been “designed” to work at in most living things.
Some of the bonds that hold enzymes in shape are broken above about 45oC destroying the “lock and key” fit.
The enzyme is denatured.
Temp
Rate of reaction
Temp (oC) 37

8. Enzymes and pH Enzymes also work best at some particular pH value.
Some (like stomach enzymes) work well in acid. Others need a neutral or alkaline pH.
If the pH is wrong for the enzyme then bonds are broken changing the shape of the enzyme and destroying the lock and key fit.
Again the enzyme is denatured. pH
Rate of reaction
0 pH 14

9. Fill in the gaps in the sentences
A catalyst will
An enzyme is …
Enzymes are obtained from …
Enzymes only work if these conditions are correct -
The important part of an enzyme is called …
The words used to describe the importance of shape are ..
An enzyme that has lost its shape is
speed up a reaction without being used up.
a biological catalyst.
living things, usually microbes such as bacteria or yeast.
temperature (usually 20-40oC) and pH.
the active site.
lock and key.
denatured.

10. Enzymes and fermentation
Yeast cells contain enzymes that convert sugars (such as glucose or sucrose) into alcohol (ethanol) and carbon dioxide.
Glucose  ethanol + carbon dioxide
C6H12O6  2C2H5OH CO2
The reaction is typically carried out between 20-30oC.
All equipment must be sterile at the start. It also has to be carried out under anaerobic conditions (the ethanol reacts with oxygen and turns into vinegar).
This production of alcohol and CO2 is known as fermentation.

11. Fermentation and wine making
Grapes use photosynthesis to convert carbon dioxide to sugar.
Wine making
Grapes are crushed to release juice which contain the sugar.
The juice is fermented under anaerobic conditions, which means without air. The natural yeast on the grape skins live on the sugar (glucose) contained in the juice.
The enzymes in the yeast convert the sugar to alcohol.

12. Fermentation and bread making
Ingredients: flour (made from wheat), water, yeast, salt sugar
Bread Making
The ingredients are mixed and the mixture left somewhere warm.
Fermentation produces carbon dioxide gas which makes the dough rise.
Warm
Cook
The bread is baked killing the yeast and evaporating the alcohol. Holes are left in the mixture where the CO2 gas was trapped.

13. Beer is usually filtered and the yeast recycled to make more beer.
Sort the statements into a flowchart that shows the process of beer making.
Beer is usually filtered and the yeast recycled to make more beer.
Yeast is added and enzymes in this convert the sugar to alcohol.
Barley grains are warmed with water to germinate. This produces sugar.
Hops are added for flavour.
Barley is boiled with water
to release the sugar.

14. Fermentation and beer making
Barley grains are warmed with water to germinate. This produces sugar.
Beer making
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.

15. Fermentation What group of substances undergo fermentation?
What provides the enzymes for fermentation?
What product is formed as well as alcohol and how can you test for this?
Why is fermentation a part of the process of bread making?
sugars, such as glucose or sucrose
yeast
carbon dioxide – it turns the limewater milky
The bubbles of carbon dioxide makes the bread rise.

16. The milk is mixed with specially cultured bacteria and kept warm.
Yoghurt making
Pasteurised or sterilised milk is used to avoid the presence of unwanted bacteria.
Yogurt making
The milk is mixed with specially cultured bacteria and kept warm.
enzymes
The enzymes from the bacteria convert milk sugar (lactose) into lactic acid which gives the sour taste and makes the product semi-solid.

17. Souring, normally done by adding cultured bacteria.
Sort the statements into a flowchart that shows the process of cheese making.
A coagulant (such as rennet) is added. This leads to (solid) curds and (liquid) whey!
Souring, normally done by adding cultured bacteria.
Whey (mainly water and lactose) is removed. The curd is salted, moulded and pressed.
As with yogurt we start with, cow’s milk. We can also use goat’s or sheep’s milk.

18. Souring normally using added cultured bacteria.
Cheese Making
As with yogurt we start with, cow’s milk. We can also use goat’s or sheep’s milk.
Cheese making
Souring normally using added cultured bacteria.
A coagulant (such as rennet) is added. This leads to (solid) curds and (liquid) whey!
enzymes
Whey ( mainly water and lactose) is removed. The curd is salted, moulded and pressed.

19. There are 7 words to do with cheese making in the square.
Find them and write down how they fit into the cheese making process.
Bacteria
Curds
Lactic acid
Lactose
Rennet
Salt
Whey

20. Biological detergents
Proteases are enzymes that break down proteins. Lipases break down fats.
Detergents
Early biodetergents used natural bacterial proteases. More recent products contain bioengineered lipases.
They work at concentrations of <1%.
bacteria
enzymes
wax coat
The enzymes are coated in a “wax” which releases them in the wash.
Here they break down fats and protein stains which are then removed by the main detergent
detergent

21. A similar process changes starch into sugar syrup.
Cane sugar (sucrose) is our normal sweetener. Glucose is also available but is less sweet.
Fructose syrup
bacillus
Enzymes are used to change glucose (from maize) into a syrup consisting of a mixture of fructose (which is very sweet) and glucose.
enzymes
+ maize
High fructose corn syrup is widely used as a sweetner by the food and drink industries.
A similar process changes starch into sugar syrup.

22. General enzyme reactions
Find or bioengineer microbes that make the appropriate enzymes.
General
get microbe
prepare nutrient
Make a solution containing the nutrients the microbes need to grow and the reactant.
mix microbe and nutrient
Add a small amount of the microbe to the solution. Keep warm, correct the pH and provide oxygen if necessary.
A fermentation takes place converting reactant to product
ferment
Separate the product.

23. Stainlesssteel reactor
Continuous enzyme reactions
The previous flow chart shows a batch process for enzyme reactions such as was used in the early manufacture of penicillin.
Large scale enzyme reactions require a continuous process where reactants and products are being fed in and removed all the time.
Stainlesssteel reactor
microbes in
nutrients
reactant
cooling
water
stirrer
air in
product out

24. Extension: Life is diverse …
Scientist Thomas Brock started probing the hot springs in Yellowstone National Park in the 1960s.
He found organisms that could live and reproduce at temperatures near 100oC.
The enzymes in these thermophilic (heat loving) bacteria work well in high temperatures where all chemical reactions occur more quickly.
One enzyme allows you to multiply a piece of DNA billions of times in a few hours which is superb news for genetic engineers and forensic scientists.
Find out why being able to multiply DNA rapidly is important.
Most enzymes stop working above about 45oC.
Can you think of other possible uses for “high temperature” enzymes?

25. Which of the following is a process that depends upon the use of enzymes?
Distillation
Fermentation
Sterilisation
Condensation

26. Which statement is NOT true about enzymes?
They are biological catalysts.
They only work over a narrow pH range
They only work below a certain temperature
They only work inside living organisms.

27. Which of the following is NOT true about enzymes becoming denatured?
Heat can denature enzymes.
Acids may denature enzymes.
When an enzyme is denatured it dies.
When an enzyme is denatured its shape changes.

28. Which statement forms a part in the “lock and key” theory of enzymes?
The enzyme acts like a key.
The reacting molecule behaves like a lock.
Only molecules with a particular shape will be acted upon by the enzyme.
The enzyme is an acid.

29. Which of the following is true of fermentation?
Fermentation is used in bread-making.
Fermentation occurs best at high temperatures.
Fermentation produces carbon monoxide.
Fermentation produces glucose.

30. Which of the following is true about yoghurt?
Yoghurt tastes sour because it contains lactose.
Yoghurt usually contains live cultures of bacteria.
Yoghurt is best made from fresh unpasteurised milk.
Yoghurt has a pH of around 10.

31. Which of the following is true about the sugar syrup made from corn (maize) and used to sweeten many drinks and foods?
Glucose is the main sweetener in this syrup.
Sucrose is the main sweetener in this syrup.
Fructose is the main sweetener in this syrup.
Lactose is the main sweetener in this syrup.

32. Which of the following is true about the enzymes contained in biological detergents?
They contain proteases to break down fats.
They contain lipases to break down sugars.
They contain bioengineered lipases.
They are coated with pvc.

33. Which of the following is NOT true about the large scale manufacture using enzymes?
They use continuous rather than batch processes.
They have accurate means of maintaining a constant temperature.
They have mechanical stirring systems to mix the reactants.
They operate at much higher temperatures.