Course
Subject
Topic
Pages
Additional
science
Biology
B2 3.1 Proteins, catalysts
and enzymes
Pages 32–33
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 that protein molecules are
made up of long chains of
amino acids
 that proteins act as
structural components,
hormones, antibodies and
catalysts
 that an enzyme is a
biological catalyst
 how enzymes work.
Most students should be able to:
 describe how long chains of amino
acids form protein molecules
 state the roles of proteins in the
formation of muscles, hormones,
antibodies and enzymes
 describe the structure and mode of
action of an enzyme.
Some students should also be
able to:
 explain in detail the concept of the
active site of the enzyme.
Protein molecules are made up of long chains of
amino acids … [B2.5.1 a)]
Catalysts increase the rate of chemical reactions …
[B2.5.1 b)]
The shape of an enzyme is vital for the enzyme’s
function … [B2.5.2 a)]
Different enzymes work best at different pH values.
[B2.5.2 b)]
Controlled Assessment: AS4.3 Collect primary
and secondary data [AS4.3.2 a) b) c) d) e) f)]; AS4.4
Select and process primary and secondary data
[AS4.4.1 a) b)], [AS4.4.2 b)]; AS4.5
Analyse and interpret primary and secondary data.
[AS4.5.4 a)]
Chapter map:
Enzymes
Teacher notes:
Enzymes
Animation:
Enzyme action
Bump up your
grade: Nearly
everything about
enzymes
Lesson structure
Support, Extend and Practical notes
Starter
Biological stains – Bring in a cheap, clean white T-shirt and allow students to
smear it with selected food and drink (tomato ketchup, mustard, egg). Discuss with
the students how they could remove the stains and get the T-shirt clean. Show the
students a box of biological washing powder and a box of non-biological washing
powder and get them to say which one would be best to use with reasons. (Care
needed if washing powders are handed around – some people can have sensitive
skin). Support students by prompting as to the nature of the stains and how they
could be broken down. Extend students by asking them to compare the contents of
the two washing powders and to say what the enzymes are, breaking down, e.g.
starches, proteins and fats. (10 minutes)
Main
Enzymes in action – The experiment ‘Breaking down hydrogen peroxide’
shows the action of manganese(IV) oxide, an inorganic catalyst, and a piece of
liver, which contains the enzyme catalase, on hydrogen peroxide.
Use a PowerPoint presentation to build up a picture of how enzymes are
composed of long chains of amino acids folded and coiled into special shapes.
Introduce the concept of the active site, enzyme specificity, how they work and
what they can do. Introduce them to the convention of naming enzymes – the ‘ase’ suffix for many – and give some examples.
Provide students with a worksheet that they can fill in as the presentation proceeds.
Catalase is present in living tissue. The more active the tissue, the greater the
catalase activity (see Practical support ‘Catalase in living tissues’ for full
details). The reactions can be described or they can be measured. (This links
to ‘How Science Works’ – making observations and measurements.) If the
experiment is to be a qualitative one, i.e. just a simple comparison of the
activity by observation, then written descriptions or comparative statements
can be made.
It is possible to make this experiment more quantitative by using the same
quantities of each tissue, and then measuring the activity when placed in the
same volume of hydrogen peroxide. Simple heights of froth up the tube in a
given time can be measured. A more accurate measurement is given by
collecting the gas evolved in a given time. (This demonstrates many ‘How
Science Works’ concepts.)
There are many variations of the catalase experiments:
 Investigate the volume of gas released when different quantities of fresh
liver are used in the same volume of hydrogen peroxide, i.e. varying the
amount of enzyme with a fixed quantity of substrate.
 The converse of this is to use the same quantity of liver and vary the
concentration of hydrogen peroxide used, i.e. varying the quantity of the
substrate with a fixed quantity of enzyme.
Plenary
Find the substrate for the enzyme – Using thin card, make sets of ‘enzymes’
of different shapes and with differently shaped ‘active sites’, and a
corresponding set of ‘substrates’ that fit into the enzymes’ ‘active sites’. (You
could adapt very simple jigsaw pieces.) Support students by making the pieces
very simple. Extend students by using more complex shapes and making the
‘substrates’ consist of two parts which fit together into the active site. Students
need to find the ‘enzyme’ and ‘substrate’ that fit together. (10 minutes)
Support
Use toy building blocks to represent large molecules, such as
starch, proteins and fats. Label each one on one side with the
name of the substrate (‘starch’, ‘protein’) then label the individual
bricks with the name of the products (‘sugars’, ‘amino acids’). Use
plastic knives with the word ‘Enzyme’ on to cut up the blocks.
Extend
Ask students to research the structure of proteins and use a length
of Bunsen tubing to demonstrate the differences between the
primary, secondary and tertiary structure. Different sequences of
amino acids can be marked with a pen and the tubing can be coiled
and twisted into a C shape to illustrate the active site.
Practical support
Breaking down hydrogen peroxide
Equipment and materials required
Manganese(IV) oxide, fresh liver, tiles and knives for cutting, test tubes,
hydrogen peroxide solution, eye protection, some method of collecting
the gas given off (syringes/inverted test tubes, rulers if height of froth to
be measured), water bath if liver is to be boiled and denatured.
Details
By adding hydrogen peroxide, students can compare the activity of the
inorganic catalyst with cubes of fresh liver and liver in which the
enzymes have been denatured by heating. The denatured liver shows
that the enzyme is present in living tissue and is destroyed by heating.
Include a test tube containing hydrogen peroxide as a control. An
additional control using a piece of boiled and cooled liver would show
that the enzyme from the living tissue can be denatured.
Safety: CLEAPSS Hazcard 33 – disposal of organic waste.
CLEAPSS Hazcard 50 Hydrogen peroxide.
Catalase in living tissue
Equipment and materials required
Fresh liver, potato tuber tissue, apple, etc., tiles and knives for cutting,
test tubes, hydrogen peroxide solution, eye protection, some method of
measuring the gas given off (syringes/inverted test tubes or
manometers; rulers if height of froth to be measured), stopwatches or
stop clocks, water bath if tissues are to be boiled and denatured.
Details
Drop small cubes of different tissues, such as liver, muscle, apple
and potato, into test tubes containing hydrogen peroxide (10 cm3 to
15 cm3 depending on the size of the tubes). If the experiment is to
be qualitative, students should record their observations, make
comparisons and write statements about the activity of the enzyme
in the different tissues. If it is to be quantitative, then the same
quantities of tissue and hydrogen peroxide should be used and
measurements taken of the activity.
Safety: Wear eye protection, CLEAPSS Hazcard 50 Hydrogen
peroxide. Take care with tubes, which can become hot.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Biology
B2 3.2 Factors affecting
enzyme action
Pages 34–35
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 that enzymes are vital to
all living cells
 that changes in
temperature affect the rate
at which enzymes work
 that different enzymes
work best at different pH
values.
Most students should be able to:
 describe experiments that show the effect
of changes in temperature and pH on the
rate of enzyme-controlled reactions
 describe how changes in temperature
and pH affect enzyme action.
Some students should also be able to:
 explain in detail how changes in
temperature and pH affect the active site
of an enzyme.
The shape of an enzyme is vital for the
enzyme’s function. High temperatures
change the shape. [B2.5.2 a)]
Different enzymes work best at different
pH values. [B2.5.2 b)]
Controlled Assessment: AS4.4 Select
and process primary and secondary data
[AS4.4.2 a) b) c)]; AS4.5 Analyse and
interpret primary and secondary data.
[AS4.5.2 a) b) c)], [AS4.5.3 a)]
How Science Works:
Does temperature
affect the speed of
an enzyme reaction?
How Science Works:
Lines of best fit and
error bars
Lesson structure
Support, Extend and Practical notes
Starters
What happens to milk when it goes off? – Show the students fresh and sour milk. If
possible, have one that is really solid but careful risk assessment is necessary. Discuss
what has happened to the milk and why putting milk in the refrigerator stops it going off.
(5 minutes)
Denaturing eggs – Crack raw eggs (or get students to do this) into three beakers: one
beaker at room temperature, one at a temperature where visible changes to the egg white
just occur, and one at boiling point. Support students by asking them to describe the visible
and textural changes to the egg white. Extend students by asking them to explain the
changes that are happening to the shape of the protein. Are the changes irreversible?
Introduce the concept of denaturation. (10 minutes)
Main
Investigating the effect of temperature on enzymes – Students can use their own saliva
to carry out this experiment on the action of amylase on starch (see Practical support
‘Investigating the effect of temperature on enzymes’).
A graph can be plotted of the rate of disappearance of starch (1/time taken in seconds)
against the temperature. Many concepts of ‘How Science Works’ can be developed in the
investigative work, e.g. hypotheses are formulated, predictions are made, variables are
controlled and conclusions drawn. Concentrate on one or two of these, e.g. drawing
conclusions from the graph plotted.
Other enzymes could be used for investigations into the effect of temperature. If the use of
the students’ saliva is not possible, commercial amylase could be used, but it is usually
derived from fungi and can give odd results.
If pepsin or trypsin (protein digesting enzymes) are used, the substrate to use is the white
of hard-boiled eggs or an egg-white suspension made by adding 5 g of egg white to 500
cm3 of very hot water and whisking briskly. The rate at which the egg-white suspension
clears can be timed at the different temperatures. More ‘How Science Works’ concepts are
introduced here too.
Investigating the effect of pH – The effects of varying pH can also be investigated by
modifying the experiments described above. Keep the temperature constant and vary the
pH by using a range of buffer solutions.
The effect of varying pH on catalase. Potato discs can be added to hydrogen peroxide and
buffer solutions and the quantity of oxygen evolved in a set time can be measured at each
pH. A graph can be plotted of volume of oxygen evolved against pH and the optimum pH
for catalase determined.
Plenaries
What temperature do I work best at? – Discuss what might be the optimum temperature
for the enzymes in the human body. What happens if we get a fever? Why do parents
worry when you get too hot? Contrast our body temperature with that of other organisms
– include some fish, reptiles and invertebrates. Do all enzymes have the same optimum
temperature? (5 minutes)
Definitions – Write up a list of the key words and phrases used in this topic so far. Support
students by providing a list of definitions which they need to match with the words. Extend
students by asking them to write their own definitions and using them to compose a short
passage which they could use as a revision card. (10 minutes)
Support
Tell students that bits of milk need to be joined together
by enzymes to make yoghurt. Make some yoghurt in a
vacuum fl ask, a water bath or preferably a commercial
yoghurt maker. Set up controls in the refrigerator and at
room temperature. Prepare a work sheet with a results
table for time taken for it to run through a funnel. Adjust
the bore so that some yoghurt will very slowly flow
through. Try it with boiled yoghurt (risk assessment).
Extend
Get students to research some of the organisms that
live in hot springs, very cold conditions and conditions
of extreme pH.
Practical support
Investigating the effect of temperature on
enzymes
Equipment and materials required
Test tubes and racks, water baths for different
temperatures, 2% starch solution, fresh saliva, boiled
saliva, iodine solution, white tiles, glass rods, eye
protection.
Details
Each student will need at least 2 cm depth of saliva in a
test tube. Test tubes should be set up containing equal
volumes of saliva and starch solution, shaken and then
placed into water baths at different temperatures.
Drops of the mixtures are then tested at 30 second
intervals for the presence or absence of starch by
dipping a glass rod into the mixture and then into a
drop of iodine solution on a white tile. Note the colour
each time and record how long it takes for the starch to
disappear at each temperature. A control could be set
up using boiled saliva.
Safety: CLEAPSS Hazcard 54B Iodine solution.
Dispose of saliva in disinfectant. CLEAPSS Hazcard 33
Enzymes.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Biology
B2 3.3 Enzymes in digestion
Pages 36–37
Learning objectives
Learning outcomes
Specification link-up
Students should learn:
 that during digestion, the
breakdown of large molecules
into smaller molecules is
catalysed by enzymes
 that these enzymes, which are
produced by specialised cells
in glands, pass out into the gut
 that the enzymes include
amylases that catalyse the
breakdown of starch,
proteases that catalyse the
breakdown of proteins and
lipases that catalyse the
breakdown of lipids.
Most students should be able to:
 explain how enzymes are
involved in the digestion of our
food
 describe the location and action
of the enzymes which catalyse
the breakdown of carbohydrates
(starch), proteins and lipids.
Some students should also be
able to:
 explain digestion in terms of the
molecules involved.
The chemical reactions inside cells are controlled
by enzymes. [B2.6.1 a)]
Some enzymes work outside the body cells … .
[B2.5.2 c)]
The enzyme amylase is produced in the salivary
glands … . [B2.5.2 d)]
Protease enzymes are produced by the stomach
… . [B2.5.2 e)]
Lipase enzymes are produced by the pancreas
and small intestine … . [B2.5.2 f)]
The stomach also produces hydrochloric acid. The
enzymes … . [B2.5.2 g)]
The liver produces bile, which is stored in the gall
bladder … . [B2.5.2 h)]
Controlled Assessment: AS4.5 Analyse and
interpret primary and secondary data. [AS4.5.2 a)
b) c) d)], [AS4.5.3 a)], [AS4.5.4 d)]
Kerboodle
Lesson structure
Support, Extend and Practical notes
Starters
What we know about enzymes so far, a quick quiz –
Ask 10 questions on enzyme structure and factors affecting their action. Support students
by making the questions simple and straightforward. Extend students by asking more
difficult questions and expecting more detailed answers. (5 minutes)
The fly – Show photographs of a fly’s mouthparts and talk through how they function, or
how a spider sucks the juice out of its victims. (For a taster, search the internet for ‘The Fly
watch trailer’). (10 minutes)
Main
Introduce the different types of digestive enzymes by reviewing the different components of
the diet. Get the students to realise that complex carbohydrates, proteins and lipids have to
be digested before they can be absorbed. Introduce the groups of digestive enzymes and
what they do. Reference to carbohydrases, proteases and lipases, their substrates and
their products is required. Project a diagram of the human digestive system and its
associated glands and indicate where the different enzymes work in the gut. Also indicate
on this diagram where the enzymes are produced as well as where they act. It could be
helpful to provide the students with an outline of the digestive system, so that they can fill
in the information for themselves.
Making a model gut – each group of students will need two 15 cm lengths of dialysis
(Visking) tubing to model the gut (see ‘Practical support’). If desired, the experiments can
be left for 24 hours at room temperature before testing.
If there is not time for the students to carry out their own experiments, then a length of
dialysis tubing can be filled with a mixture of 30% glucose solution and 3% starch solution
and placed in a test tube of distilled water. If this is left for about 15 minutes, the water can
be tested for starch and glucose.
Some glucose should have diffused through the tubing into the water, but the starch should
not. Tests for starch and glucose will confirm this. Note: This only demonstrates that
glucose will pass through the tubing but starch will not; it does not show that the enzyme
catalyses the breakdown of the starch.
The model gut can be used to show the effect of changes in temperature and pH on the
activity of saliva or amylase on starch. The tubing should be placed in boiling tubes, and
samples of the water surrounding the tubing can be tested for starch and sugars at
intervals to determine whether or not digestion has taken place.
To investigate changes in temperature, the boiling tubes containing the enzymesubstrate
mixtures in the tubing should be incubated in a range of temperatures from about 5 °C to
60 °C using water baths.
To investigate the range of pH values, buffer solutions should be used, providing another
opportunity to develop the investigative aspects of ‘How Science Works’, such as evaluation.
Plenary
Cryptic word search – Support students by giving them a wordsearch of the enzymes,
substrates and products from the lesson. Extend students by getting them to write cryptic
definitions of the words and using them to test each other. (10 minutes)
Support
Use flip cards with foods on one side and their
components on the other. Some students might need a
clue, such as starting letters or vowels. Alternatively,
use an internet version for whiteboards, or individual
computers such as those created through ‘Quia’ (use
this as a search term).
Play floor dominoes. Make up large ‘domino’ cards of
food types, their components and the enzymes and
allow the students to play in groups.
Extend
Get students to research how cystic fibrosis affects the
digestive system and the use of enzymes in its
treatment.
Practical support
Investigating digestion
Equipment and materials required
Visking or dialysis tubing, dropping pipettes, elastic
bands, starch and enzyme solutions (the concentration
of these solutions may need to be increased to give
results in a single lesson), water baths, beakers, test
tubes and racks, iodine solution, Benedict’s solution.
Details
Each group of students will need two 15 cm lengths of
dialysis (Visking) tubing, which has been soaked in
water. Each piece should be knotted securely at one
end. Using a dropping pipette, fill one length of the
tubing with 3% starch solution and place it in a test
tube. Fold the top of the tubing over the rim of the test
tube and secure with an elastic band. Remove all
traces of the starch solution from the outside of the
tubing by filling the test tube with water and emptying it
several times. Finally, fill the test tube with water and
place it in a rack. Repeat the procedure with the
second length of tubing but add 5 cm3 saliva or
amylase solutions to the starch solution, and shake
before filling the dialysis tubing. The test tubes should
be labelled A and B and placed in a water bath at 35 °C
for 30 minutes. The water in the test tubes should then
be tested for: starch, using iodine solution; sugars,
using Benedict’s solution.
Safety: CLEAPSS Hazcard 54B Iodine solution. CLEAPSS
Hazcards 27C and 95A Benedict’s solution – harmful.
CLEAPSS Hazcard 33 Enzymes. Wear eye protection.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Biology
B2 3.4 Speeding up
digestion
Pages 38–39
Learning objectives
Learning outcomes
Specification link-up
Students should learn:
 that the enzymes in the stomach
work most effectively in the acid
conditions resulting from the
production of hydrochloric acid
by the stomach
 that bile produced by the liver
provides the alkaline conditions
needed for the enzymes in the
small intestine to work most
effectively
 that bile also emulsifies the fats
increasing the surface area for
the enzymes to act upon.
Most students should be
able to:
 describe how pH affects the
enzymes in the different
parts of the gut
 describe how bile emulsifies
fats.
Some students should also be
able to:
 explain in detail how the
emulsification of fats
increases the rate of their
digestion.
Some enzymes work outside the body cells … . [B2.5.2 c)]
The enzyme amylase is produced in the salivary
glands … . [B2.5.2 d)]
Protease enzymes are produced by the stomach … .
[B2.5.2 e)]
Lipase enzymes are produced by the pancreas and
small intestine … . [B2.5.2 f)]
The stomach also produces hydrochloric acid. The … .
[B2.5.2 g)]
The liver produces bile, which is stored in the gall
bladder … . [B2.5.2 h)]
Controlled Assessment: AS4.1 Plan practical ways
to develop and test candidates’ own scientific ideas
[AS4.1.1 a) b) c)]; AS4.4 Select and process primary
and secondary data. [AS4.4.2 a) b) c)]
Kerboodle
Lesson structure
Support, Extend and Practical notes
Starters
Effect of body temperature on digestion – Show a picture or footage of a reptile,
such as a snake or a crocodile, eating a large lump of meat and show a picture of
lions feeding. Ask: ‘What consequences will their different body temperatures have
on the rate at which they digest their meals? How often do they feed the reptiles in
the zoo?’ Students to make a list and compare. (5 minutes)
More about surface area – Get students to tell you what they know about SA (surface
area) to volume ratio. Ask them to think about how this might be relevant to the process of
digestion. Discuss the effect of the teeth and mastication on the break up of large masses
of food in the mouth. Ask: ‘What is the effect on digestion in the mouth? Does chewing
affect digestion in the stomach?’ Support students by reminding them of how SA (surface
area) increases when the volume is decreased. Extend students by asking them to think
about other examples of the importance of SA (surface area) in the process of digestion
(e.g. chewing, absorption). (10 minutes)
Main
The practical on ‘Breaking down protein’ described in the Student Book is easy to set
up (see ‘Practical support’). The experiment can be made more quantitative
(introducing ‘How Science Works’), by getting the students to formulate an
hypothesis, make predictions, use stated volumes of enzyme and acid and weigh the
pieces of meat used at the beginning and end of the experiment. A bar chart can be
drawn showing the percentage change in mass.
Compare the action of pepsin with the action of trypsin. Pepsin and trypsin work in
different parts of the gut in different pH conditions. The experiment (‘Effect of pH on
enzyme action’) described in ‘B2 3.2 Factors affecting enzyme action’ could be used
here to show that pepsin works best in acid conditions and trypsin in alkaline
conditions. If specific pH values are required, then the use of buffer solutions is
recommended.
Ask the students what the word ‘emulsion’ means (paint it on to a large sheet of
paper – using emulsion paint). Bring in a salad, some vinegar and some olive oil. Get
a student to pour some oil on top of the vinegar in a gas jar or similar vessel, shake
vigorously and produce an emulsion. Students can do this themselves on a small
scale in a boiling tube. Observe the globules formed and link to SA (surface area),
then to speeding up digestion. Link the formation of an emulsion with the effect of
bile salts.
An experiment could be set up to demonstrate the effect of bile salts on the activity
of lipase (see ‘Practical support’).
Plenaries
Gallstones – Show some gallstones or photographs of gallstones. Discuss why
gallstones occur and what might be the consequences. Get the students to write a
letter to their doctor stating what problems they fear and asking advice. (5 minutes)
Colouring exercise: The pH in the gut – Give the students unlabelled diagrams of
the digestive system and ask them to label them and colour in the different regions
according to the different pH conditions that exist in the gut. Support students by
giving them the list of different pH conditions. Extend students by getting them to
work out the different regions and to add the names of the major enzymes present in
each region. (10 minutes)
Support
Get students to illustrate the formation of an emulsion.
Extend
Get students to find out more about bile. What does it
contain? How and where is it made?
Practical support
Breaking down protein
Equipment and materials required for each group:
At least three test tubes and a rack, small cubes of meat, 2%
pepsin solution, 0.1 M solution of hydrochloric acid, water
bath at 35 °C, balance, labels, filter papers, eye protection.
Details
Each group of students will require three test tubes and can
set up their own experiment. Into one test tube, place about
20 cm3 of pepsin solution. Into a second tube place the same
volume of hydrochloric acid and into a third tube place the
same volume of a mixture of pepsin solution and hydrochloric
acid. Cut three similar sized chunks of meat, weigh each one
and place one piece into each of the three tubes, noting
which piece of meat was placed into which tube. Leave for a
few hours. An additional control tube could be added using
boiled and cooled pepsin. If this done, it would be advisable
to leave the experiment running for 24 hours. The pieces of
meat should then be removed from the tubes, rinsed and
dried on filter paper before reweighing.
Safety: Wear eye protection.
Demonstrating the effect of bile salts on the activity of
lipase
Equipment and materials required
Two test tubes, 5 cm3 of milk, 7 cm3 sodium carbonate
solution and 5 drops of phenolphthalein, washing up liquid, 2
cm3 of lipase.
Details
Set up two test tubes, each containing 5 cm3 of milk, 7 cm3
sodium carbonate solution and 5 drops of phenolphthalein.
To one tube, add a drop of washing up liquid. Add 1 cm 3 of
lipase to each tube and stir each tube, timing how long it
takes for the indicator to go from pink (alkaline) to colourless
(acid) showing that the lipids in the milk have been broken
down to fatty acids. The washing up liquid emulsifies the
lipids and the reaction should therefore be quicker.
Safety: CLEAPSS Hazcard 33 Enzymes. Wear eye protection.
Wash hands if reagents come into contact with the skin.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Biology
B2 3.5 Making use of
enzymes
Pages 40–41
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 that enzymes from
microorganisms have many
uses in the home and in
industry
 that proteases and lipases are
used in the manufacture of
biological detergents
 that proteases, carbohydrases
and isomerase are used in
food manufacture.
Most students should be able to:
 explain how biological detergents work
 describe some of the ways in which
enzymes are used in the food
industry.
Some students should also be able to:
 evaluate the advantages and
disadvantages of using enzymes in
home and in industry.
Some microorganisms produce enzymes
that pass out of the cells … . [B2.5.2 i)]
In industry, enzymes are used to bring
about reactions … . [B2.5.2 j)]
Controlled Assessment: AS4.1 Plan
practical ways to develop and test
candidates’ own scientific ideas.
[AS4.1.1 a) b) c)]
Maths skills:
Enzymes and rates
Support: Enzyme
memory
Practical: Biological
and non-biological
washing powders
Lesson structure
Support, Extend and Practical notes
Starters
Taste tests
Fructose is now available in many supermarkets. You could make up separate solutions of
fructose, sucrose and glucose of the same strength (e.g. 2 teaspoons in a beaker of water)
and get the students to do a blind tasting scoring them for sweetness on a 5-point scale.
Note: this must be done in hygienic conditions following risk assessment and not in a
laboratory. (5 minutes)
Baby food for lunch?
Show the students some samples of baby food. Have disposable plastic spoons and be
prepared for joking. Some pelican bibs will help to create the atmosphere. Ask: ‘How does
baby food differ from adult food? What did parents do before the commercially prepared
baby foods were available?’ Compile lists on the board and compare. Support students by
prompting them to suggest how enzymes might be involved. Extend students by asking
them to list the processes involved in the commercial production of baby food. (10 minutes)
Main
Use agar plates containing starch, milk and mayonnaise (or salad cream or egg yolk) to
demonstrate the activity of enzymes in biological detergents (see ‘Practical support’). This
activity can be used to compare different biological washing powders or liquids (the
advantage of liquids is that volumes can be measured and dilutions made more easily). It
can also be used to compare dishwasher detergents with clothes washing detergents and
to discover whether the age of the detergent has any effect on its efficiency.
All of these can be used to introduce many ‘How Science Works’ concepts. Predictions can
be made, measurements made and recorded, variables controlled and conclusions drawn.
It also gives students some scope for designing their own investigations.
The experiment above can be modified to demonstrate that the proteases in a biological
detergent can work at higher temperatures than trypsin from an animal source. Samples of
both can be heated to temperatures of 30 °C, 40 °C, etc. and then placed in holes in milk
agar plates. Use a separate plate for each enzyme or detergent tested and the number of
holes should correspond to the number of different temperatures tested. The plates should
then be treated as above and the clear areas measured and recorded. A graph can then
be plotted of temperature against area of clear zone.
The effect of biological detergent on egg albumin can be demonstrated by immersing
cubes of egg white in a solution of a biological detergent. A solution of a biological washing
powder is made by dissolving 3 g of powder in 30 cm3 of water. A cube of egg white is
weighed and placed in this solution for 20 minutes, after which time it is removed, rinsed
and dried. The effect of the washing powder can be assessed by reweighing.
This investigation can be expanded to consider different variables. Comparisons can be
made using different biological detergents. The strength of the detergent needed can be
investigated and the optimum temperature found.
Plenary
Enzymes table
Give the students two minutes to write down as many advantages and disadvantages of
using enzymes in commercial processes as they can. Gather together the suggestions and
build up a table of advantages and disadvantages. Discuss how the disadvantages can be
overcome. (5 minutes)
Support
Use name boards with a fold-over end. Write
‘carbohydrate’ on one and use the hinged fold-over to
convert it into ‘carbohydrase’. Have examples of all the
enzymes required in the specification.
Extend
Ask students to find out the differences in the structural
formulae of glucose and fructose. They can try to work out
why these sugars have different effects on the taste buds.
Practical support
Investigating biological washing powder
Equipment and materials required
Some biological detergent (either in powder or liquid
form in order to make up different concentrations if
needed – avoid contact with skin), egg white in
chunks/cubes (or agar plates containing starch, milk,
mayonnaise, salad cream or egg yolk), test tubes and
racks, tissues for drying, iodine solution (CLEAPSS
Hazcard 54B) balance for weighing, eye protection,
protective gloves.
Details
A cork borer is used to remove cylinders of agar from
the prepared plates. The number of cylinders removed
depends on the number of detergents being tested. Into
the holes, solutions of the detergents can be placed
and the plates incubated at 25 °C for about 24 hours.
Iodine solution is poured over the starch-agar plate and
left for 5 minutes before being poured away. The
diameter of clear areas around the holes can be
measured and recorded. It should be possible to
measure clear areas around the holes on the milk-agar
plates and the mayonnaise-agar plates.
Safety: Care when handling detergents. CLEAPSS
Hazcard 54B Iodine solution. Eye protection and
protective gloves needed.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011
Course
Subject
Topic
Pages
Additional
science
Biology
B2 3.6 High-tech enzymes
Pages 42–43
Learning objectives
Learning outcomes
Specification link-up
Kerboodle
Students should learn:
 that there are advantages
and disadvantages to using
enzymes at home and in
industry
 that enzymes can be used
as diagnostic tools in
medicine and in the
treatment of some diseases.
Most students should be able to:
 describe some of the advantages and
disadvantages of using biological
detergents
 describe some of the ways in which
enzymes are used in medicine.
Some students should also be able to:
 evaluate the advantages and
disadvantages of using enzymes in the
home and in industry.
Evaluate the advantages and
disadvantages of using enzymes
in the home and in industry. [B2.5]
Controlled Assessment: AS4.1
Plan practical ways to develop and
test candidates’ own scientific
ideas. [AS4.1.1 a) b) c)]
Interactive activity: Enzymes
Podcast: Enzymes
Test yourself: Enzymes
On your marks: Enzymes
Examination-style questions:
Enzymes
Answers to examination-style
questions: Enzymes
Chapter map: Enzymes
Lesson structure
Support, Extend and Practical notes
Starters
A question of temperature – Some washing machine cycles can operate at temperatures
as low as 30 °C. Ask: ‘Is this always a good thing?’ Draw up a balance sheet of advantages
and disadvantages of the lowering of the temperature. Ask: ‘Do the advantages outweigh
the disadvantages? Would you wash your baby’s dirty clothes in a low temperature wash?’
(5 minutes)
Will it come out in the wash? – Get students to suggest stains they might get on
their clothes and build up a list. Add a few of your own suggestions (such as tar,
ballpoint pen, etc.). Then ask which ones will come out if the clothes are washed with
a biological detergent. Support students by making the list fairly simple and
reminding them about the enzymes in the detergent. Extend students by including
some more unusual examples (chilli sauce!) and get them to identify the class of
enzyme that would get rid of the stain. (10 minutes)
Main
Clinistix and albustix can be used to test for the presence of glucose and protein in
urine. Carry out a ‘Tinkle test’ experiment with fake urine doctored with glucose,
protein, both and neither. Discuss the benefits of such tests compared with the
standard methods of testing for glucose and protein in the lab (using Benedict’s
solution and the Biuret test). Discuss the value of the tests in making quick
diagnoses and helping people with diabetes to control their condition.
Discuss the problems of cystic fibrosis and the use of enzymes in its treatment. Tell
students about the consequences of the blocking of the pancreatic duct. Ask the
students what they think the consequences could be and how the problem could be
overcome. Show the video Sammi’s story (Channel 4 Television, 1995) if available or
go to the cystic fibrosis website for more information about the treatment.
Use the internet to research other uses of enzymes in medicine, such as
streptokinase for heart attacks and a treatment for childhood leukaemia. Allow the
students to carry out their own research or prepare a PowerPoint presentation with a
worksheet for the students to complete.
Carry out the poster activity ‘Enzymes in medicine’ recommended in the Student
Book. It would be quite difficult to include masses of information on one poster so
students could decide to make a series of posters about different uses of enzymes,
along the lines of ‘Did you know that … streptokinase is used to treat heart attacks?’
etc. Use could be made of ICT in the design and production of the posters.
Students could carry out the activity suggested in the Student Book and design an
experiment to compare the effectiveness of a biological detergent with an ordinary
detergent at 40 °C. Encourage students to think about the variables that need to be
controlled and the way in which they are going to assess the results. They should be
able to use the knowledge they have gained from setting up the enzyme experiments
described in other spreads.
Plenaries
Enzyme anagrams round-up – Prepare anagrams of the enzymes mentioned in
this chapter. Students could be supported by using the simpler, straightforward ones.
Students could be extended by including more enzymes and/or leaving out the
vowels. (5 minutes)
The perfect detergent – Students, in groups, could decide on the most favourable
properties that a clothes-washing detergent should have and then give it a name and
design a simple poster advertising its advantages. There should be good scientific
reasons behind the claims made for its efficacy! Posters could be displayed around
the classroom. (10 minutes)
Support
Provide students with the text and pictures with which to build
up a poster on ‘Enzymes in medicine’.
Extend
Get students to find out more about unusual enzymes, such
as bromelain and papain, and their uses in the food industry.
Text © Ruth Miller, Geoff Carr, Darren Forbes, Sam Holyman 2011