Practical’s
Practical 1
Learning objectives:
 By the end of the lesson you should be able to


State the similarities and differences between animal, plant
and microbial cells.
Describe the function of cell structures namely the nucleus,
cytoplasm, cell membrane, cell wall , chloroplast and vacuole.
Introduction
0.1 mm in size and so are
 Cells are usually less than _______
Stains
too small to see without a microscope._________
can
also be used to show up the cell structures more
clearly.
Aim
 To look at a variety of cells in order to identify cell
structures
Method
 Your teacher will show you how to present wet slides of
a variety of plant and animal specimens using different
stains as appropriate. These will include:
 Cheek Epithelium
 Elodea
 Onion Epidermis
 Rhubarb Epidermis
 Look at each specimen down the microscope and use
high magnification to see detail of structures in each
cell.
 Complete a results grid for each specimen observed
Specimen Structures
Visible
Stain
Plant or
Animal
Reason
Magnifi Drawing
cation
Cheek
Epithelium
Cell
Membrane
Cytoplasm
Nucleus
Methylene
Blue/
iodine
solution
Animal
No cell
wall
present
x200
Elodea
Cell Wall
Chloroplasts
Plant
Cell wall
present
x100
Onion
Epidermis
Cell Wall
Cytoplasm
Nucleus
Plant
Cell wall
present
x100
Rhubarb
Epidermis
Cell Wall
Plant
Cell Wall x100
present Cell wall
Vacuole
Iodine
Solution
Vacuole
Conclusion
Which structures can be
identified in the various cells?
 The cell wall,
 Cell membrane
 Cytoplasm
 Nucleus
 Chloroplast and Vacuole
Evaluation
How are the structures in
some cells made easier to
see?
 Using stains and high
magnification
Practical 2
Learning objective
 By the end of the lesson you should be able to:

Describe the commercial and industrial uses of cells in:
 Alcohol production
Introduction
 Yeast can use sugar as a food source in anaerobic
conditions. Under these conditions it will carry out
fermentation.
Aim
 To demonstrate the changes that take place in a
fermenter.
Method
Your teacher will set up a fermenter containing sugar
and yeast solution. Any gas produced will bubble
through lime water.
2. Measure and record the temperature and pH of the
sugar and yeast solution. Smell the contents of the
fermenter and note the appearance of the lime water.
Record this information in the results table.
3. After 24 hours, measure and record the temperature
and pH again. Smell the contents of the fermenter
and examine the lime water.
4. Record the results in the results table.
1.
Results
Time
(hours)
Temperature pH
(oC)
Smell
Lime water
27
alcohol
cloudy
0
24
1-2
Conclusion
What is produced during fermentation as shown by the tests?
Test
Smell
Product
Ethanol/Alcohol
Lime Water
cloudy
Turned ___________
showing
Carbon dioxide
____________________
was produced
pH
Carbon dioxide
The pH fell because ________________
is an acidic gas
Temperature (oC)
increased showing that
Temperature _________
Heat energy
___________________
was produced
What does this evidence support?
The equation for alcoholic fermentation
Evaluation
 How can this experiment be improved?
 By including a control ( a fermenter set up without
yeast), to show that it is the yeast which is causing the
changes.
Practical 3
Learning Objectives
 By the end of the lesson you should be able to:

Describe the commercial and industrial uses of cells in Bread
making
Introduction
 Yeast can use sugar as a food source in anaerobic
conditions. Under these conditions it will carry out
fermentation.
 Yeast is used in bread making
To produce the carbon dioxide which makes dough rise
__________________________________________________
Aim
 To show the effect of yeast on dough
Method
 Weigh out 20g of the flour/sugar mixture onto each




of 2 small pieces of paper.
Measure out 20cm3 of water into 1 beaker and 20cm3
of yeast suspension into another beaker.
Add one portion of flour to the water and the other to
the yeast suspension and stir with stirring rods.
Pour the dough into 2 labelled plastic beakers.
Record the volume and put the cylinders into a water
bath set at 30oC. START THE STOPCLOCK.
Record the volume of the dough at 5minute intervals
for 30mins
Results
Time
(minutes)
Volume of dough
without yeast (cm3)
Volume of dough with
yeast (cm3)
0
1
1
5
1.2
1.2
10
1.2
1.5
15
1.2
2
20
1.2
2.5
25
1.2
3
30
1.2
3.5
Analysis
 Draw one line graph to show both sets of results
70
60
Height
of
dough
(mm)
50
40
Dough with
yeast
30
Dough
without yeast
20
10
0
0
5
10
15
20
Time (Minutes)
25
30
Conclusion
 What conclusion can be drawn from the results?
 Yeast causes the dough to rise
 What is varied in this experiment?
Only the presence of yeast
Evaluation
 What steps are taken to make this experiment
Reliable, Accurate and Valid?
Same mass of flour and sugar
Same volume of liquid
Kept at the same temperature
Left for the same time
Practical 4
Learning objective
 By the end of the lesson you should be able to:

Describe the commercial and industrial uses of cells in:
 Antibiotic production
Introduction
Prevent the growth or kill
 Antibiotics are chemicals which can ______________





bacteria
____________________
Many antibiotics are produced by fungi.
Discs of paper can be soaked in different antibiotics and
different strengths (concentrations of antibiotics)
Nutrient agar in a petri dish
Bacteria can be grown on _________________________
Agar is a jelly made of seaweed which has food added to
it that bacteria can use.
Cloudy areas on the agar show where bacteria are
growing.
Sterile technique must be used to prevent
contamination by disease causing bacteria and to
prevent the spread of the bacteria that are being grown.
Aim
 To show the effect of different antibiotics on the growth of
a bacterium
Method
1. Your teacher will spread bacteria from the culture onto
a nutrient agar plate using sterile technique.
2. Discs of Streptomycin and Penicillin are placed onto
the surface of the plate as shown in the diagram.
3. The plate is taped up, labelled and incubated at
37 oC for 48 hours.
4. Examine the plate and draw its appearance
Results
 Conclusion
 What does the clear agar show?
 That the antibiotic has




prevented the growth of the
bacterium.
What is the effect of the
penicillin on the growth of the
bacterium?
has no effect on the
Penicillin _____________
growth of the bacterium.
What is the effect of
streptomycin on the bacterium?
INHIBITS
Streptomycin ___________
the
growth of the bacterium
Evaluation
 What control should be set up in this experiment?
A plate containing the bacterium and discs without any
antibiotics
Practical 5
Learning objectives:
 By the end of the lesson you should be able to:


Describe the commercial and industrial uses of cells in:
Yoghurt production
Introduction
 When milk is kept at a warm temperature
Bacteria
will start to grow
___________________________
and
“sour”
turn it _________
Because of acid production
_______________________
 Some types of bacteria will do this and
Turn the milk into yoghurt
___________________________________
Heated to high temperatures to kill all the
 UHT milk has been _____________________________
Bacteria,
__________
it is sterile
Aim
 To show acid production by the action of
yoghurt bacteria on milk
Method
1.
2.
3.
4.
5.
Add 10cm3 of UHT milk into each of two clean test
tubes labelled A and B
Add 1cm3 of yoghurt bacteria to tube A and 1cm3 of
sterile water to tube B
Incubate the tubes at 30oc for 24 hours
Examine the tubes and record the appearance in
your results table
Test the pH of each tube with universal indicator
and record your result.
Results
Tube
A
B
Appearance
pH
Conclusion
• What is the effect of the bacteria on the
pH of the milk?
 The bacteria cause the pH to fall, become more
acid
Evaluation
 How could this apparatus be used to show how
temperature affects the process?
• Set up identical test tubes with milk and yoghurt
bacteria
• Incubate at different temperatures
• Compare appearance and pH