Enzymes are protein molecules that act as biological catalysts, increasing the rate of chemical reactions. They are specific and only catalyze one reaction. Enzymes are found in animals, plants and microorganisms and are used widely in the home and industry. Some advantages of using enzymes include enabling reactions to occur at lower temperatures and making industrial processes cheaper. However, enzymes are sensitive to temperature and pH changes.

1. Enzymes
AQA Unit 2 Additional Biology

2. Proteins have many functions, both inside and outside the cells
of living organisms. Proteins, as enzymes, are now used widely
in the home and in industry.
B2.5 Proteins – their functions and uses
You should be able to:
■ evaluate the advantages and disadvantages of using
enzymes in the home and in industry.

4. ENDOCRINE SYSTEM
Pituitary
Thickens
womb wall
Insulin
Oral
contraceptive
Travels in
e.g.e.g.
e.g
. e.g
.
controls
secretes
used in
consists of
secrete
are
inhibits
secretes.
has
less
Bloodstream
Blood sugar
Chemical messengers
FSH
Glands
LH
Hormones
Oestrogen
Ovary
Matures egg
Pancreas
Progesterone
Releases egg
Side effects

5. ENDOCRINE SYSTEM
Glands Bloodstream
Hormones
Matures egg
LH
Oestrogen
FSH
OvaryPituitary
Thickens
womb wall
Releases
egg
Insulin
Pancreas
Oral
contraceptive
Side effects
Progesterone
Travels in
e.g.e.g.
e.g
. e.g
.
Blood sugar
controls.
secretes.
used in
consists of
secrete
Chemical
messengers
are
inhibits
secretes.
has
less

6. Proteins
Structural
tissues eg
muscles
Antibodies Hormones Enzymes
Amino acids –
about 20 different
types

7. What are enzymes and what do
they do?
Enzymes are-
• Protein molecules (made up of amino acids)
• Biological catalysts (Increase the speed of
chemical reactions)
• Specific (Each one catalyses one particular
reaction)
• Reusable (Can be used again and again)
• Affected by temperature and pH.
• Found in animals, plants and microorganisms.

8. P
C
R
S
T
A
pH
arents
an
eally
truggle
o
ttend
ysics
P
C
R
S
T
A
pH
roteins
atalysts
eusable
pecific
emperature
ffected

9. 2 main types of enzymes
• Catabolic enzymes which (break down) large
molecules into smaller molecules
e.g. digestion of starch by the enzyme amylase
into glucose.
• Anabolic enzymes which (build up) small
molecules to form larger molecules
e.g. production of glucose during photosynthesis
from carbon dioxide, water and light.

10. Catabolic enzymes Anabolic enzymes
enzymes
Break down Build up
Digestion Photosynthesis

11. Enzymes and activation energy
• Chemical reactions take place when
particles collide with enough energy.
• The minimum amount of energy required
is called the activation energy.
• Enzymes lower the amount of activation
energy required, so the reaction can
proceed at a greater rate.

12. • Enzymes are
proteins made up on
long chains of amino
acids.
• These long chains
fold to produce a
special shape which
is vital for the
enzyme’s function.
Active
Site
Structure of an
enzyme molecule

13. How enzymes work

14. Step-by-step
• Shape of the enzyme’s active site is
complimentary to the shape of one particular
substrate.
• The two bind together to form an enzyme-
substrate complex.
• The reaction between them take place rapidly.
• The products are released from the enzyme’s
active site.
Complete Qu 1-8 page 12.

15. Enzymes
1. Enzymes ………….. up the rate of chemical …………………..
2. Enzymes are ………………….. because they only work on one substrate.
3. The substrate fits into the ………………….. site of the surface of the
…………………...
4. With an increase in ………………….. the rate of reaction
…………………..
5. Enzymes can be re-used, so only ………………….. amounts are needed.
6. To which group of chemical compounds do enzymes belong?
7. Why is an enzyme specific for a particular substrate?
8. Why can an enzyme be used again and again?

16. Factors affecting enzyme action -
Temperature
• Enzymes work faster
as the temperature
increases up to 40o
C,
but are eventually
denatured at about
60o
C.
• This is because the
shape of the active
site is lost.

17. Factors affecting enzyme action
– pH
• Each enzyme works best at a particular pH. This is known as the
optimum pH.
• Extremes of pH will cause the active site to denature.

18. 11. A number of factors can alter the rate of an enzyme- controlled
reaction. Say what each of the following would do to the rate of reaction
and give your reasons.
An increase in enzyme concentration
…………………..…………………..…………………..…………………..
…………………..…………………..…………………..…………………..
A decrease in temperature
…………………..…………………..…………………..…………………..
…………………..…………………..…………………..…………………..
A lowering of pH
…………………..…………………..…………………..…………………..
…………………..…………………..…………………..…………………..

19. Enzymes in digestion
• Enzymes break down large
insoluble food molecules
into smaller, soluble ones
which can be absorbed
through the small intestine
wall to enter the
bloodstream.
• Different parts of the
digestive tract have different
pH conditions to enable
different enzymes to work.

20. The main groups of digestive
enzymes
• Lipase enzymes
digest fatty
substrates.
• Protease enzymes
digest protein
substrates.
• Carbohydrase
enzymes digest
carbohydrate
substrates.

21. Substrate Enzyme Product Where
enzyme
produced
Optimum
pH
Starch Amylase
(a carbohydrase)
Glucose Salivary
glands &
pancreas
pH7
Protein Trypsin
(a protease)
Amino
acids
Stomach,
pancreas,
& small
intestine
pH3
Lipids Lipases
(fats)
Fatty
acids &
glycerol
Pancreas pH8

22. The action of bile
• It’s produced by the liver and is stored in
the gall bladder which, squirts it into the
small intestine.
• It’s alkaline to neutralise acidic chyme
coming from stomach.
• It emulsifies fats to break them into
smaller droplets which increases the
surface area for lipase enzymes to work.

23. Lipase is an enzyme that breaks down fats. We can use an indicator to
follow this reaction. The indicator is red to start with but turns yellow when
all the fat has been broken down. Look at the results table below.
Test-tube Temp (°C) Original colour Final colour
1 0 Red Red
2 10 Red Orange
3 40 Red Yellow
4 60 Red Orange
5 100 Red Red
What is the optimum temperature for lipase? …………………..
Why do you think the colour didn’t change in test tube 1?
…………………..…………………..…………………..…………………..
Why do you think the colour didn’t change in test tube 5?
…………………..…………………..…………………..…………………..
Predict what you think would happen if you warmed test tubes 1 and 5 up
to 40 °C. Try to explain your prediction.

24. 13 Which enzymes work on carbohydrates? …………………..
14. Which enzymes work on proteins? …………………..
15.Which enzymes work on fats? …………………..
Name the products which are formed in each case.
…………………..…………………..…………………..…………………..
………………………………..…………………..…………………..
…………………..……………
Name 3 functions of bile …………………..…………………..…………………..
…………………..…………………..………………………..…………………..
…………………..…………………..
…………………..…………………..…………………..…………………..……………

25. i) Some microorganisms produce enzymes that pass out
of the cells. These enzymes have many uses in the
home and in industry.
In the home:
■ biological detergents may contain protein-
digesting and fat-digesting enzymes (proteases and
lipases)
■ biological detergents are more effective at low
temperatures than other types of detergents.

26. Advantages Disadvantages
These are more efficient at
removing stains from
clothes.
If the clothes are not fully
rinsed, protease enzymes
may remain in the clothes,
which digests protein in
the skin.
Lower washing
temperatures can be used
which saves energy.
This can lead to irritation,
allergies and dermatitis.

27. In industry:
■ proteases are used to ‘pre-digest’ the protein in
some baby foods
This reduces how much the baby needs to digest
the food
■ carbohydrases are used to convert starch into
sugar syrup
This is cheaper than extracting sugar from sugar
cane
■ isomerase is used to convert glucose syrup into
fructose syrup, which is much sweeter and therefore
can be used in smaller quantities in slimming foods.

28. Advantages Disadvantages
Enzymes enable industrial
reactions to take place at lower
temperatures.
Enzymes are sensitive to
temperature and pH changes.
Supplying heat is expensive.
When enzymes are used,
industrial processes can be
cheaper.
Temperature and pH need to
be carefully monitored and
controlled, which can be
expensive.
j) In industry, enzymes are used to bring about reactions
at normal temperatures and pressures that would
otherwise require expensive, energy-demanding
equipment. However, most enzymes are denatured at
high temperatures and many are costly to produce.

29. Commercial use of enzymes
Product Enzymes Explanation
Biological washing
powder
Lipases and
proteases
Digest biological
stains off clothes.
Baby food Proteases Pre-digest protein to
make digestion
easier for babies.
Slimming foods Isomerase
(carbohydrase)
Converts glucose
into fructose (less of
which is needed to
sweeten food).

30. In 1989 a new fat digesting enzyme was found in a fungus. Its optimum pH is 7.5.
It can act at low temperatures and after a few days, breaks down into carbon
dioxide, nitrogen and water. Give 2 reasons why this enzyme is now used in
washing powder
…………………..…………………..…………………..…………………..…………….
…………………..…………………..…………………..…………………..………………
Why would a washing powder of high pH or low pH be difficult to handle?
…………………..…………………..…………………..…………………..………………
…………………..…………………..…………………..…………………..………………

31. Complete the diagram below to show how the three main food groups are broken down
during digestion.
Amylase Amino acids Fat Fatty acids Glycerol Maltose Protease
Protein
Lipase
Protease
Amino acids
Fat Glycerol Fatty acid

32. Complete the diagram below to show how the three main food groups are broken down
during digestion.
Amylase Amino acids Fat Fatty acids Glycerol Maltose Protease
Protein
Carbohydrate eg starch
Amylase
Maltose