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.

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

Cells are usually less than _______ in size and so are too small to see without a microscope._________ can also be used to show up the cell structures more clearly.

AimTo look at a variety of cells in order to

identify cell structures

0.1 mm Stains

MethodYour 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

StructuresVisible

Stain Plant or Animal

Reason Magnification

Drawing

CheekEpithelium

Cell MembraneCytoplasmNucleus

MethyleneBlue/ iodine solution

Animal No cell wall present

x200

Elodea Cell Wall Chloroplasts

Plant Cell wall present

x100

OnionEpidermis

Cell WallCytoplasmNucleus

Iodine Solution

Plant Cell wall present

x100

Rhubarb Epidermis

Cell Wall

Vacuole

Plant Cell Wall present

x100

Cell wall

Vacuole

ConclusionEvaluation

The cell wall,Cell membraneCytoplasmNucleusChloroplast and Vacuole

Using stains and high magnification

Which structures can be identified in the various cells?

How are the structures in some cells made easier to see?

Practical 2

Learning objectiveBy the end of the lesson you should be able to:

Describe the commercial and industrial uses of cells in: Alcohol production

IntroductionYeast can use sugar as a food source in

anaerobic conditions. Under these conditions it will carry out fermentation.

AimTo demonstrate the changes that take

place in a fermenter.

Method

1. 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.

Results

Time(hours)

Temperature(oC)

pH Smell Lime water

0

24 27 1-2 alcohol cloudy

ConclusionWhat is produced during fermentation as shown by the tests?

Test Product

Smell

Lime Water Turned ___________ showing ____________________ was produced

pH The pH fell because ________________ is an acidic gas

Temperature (oC) Temperature _________ showing that ___________________ was produced

What does this evidence support?The equation for alcoholic fermentation

Ethanol/Alcoholcloudy

Carbon dioxide

Carbon dioxide

increasedHeat energy

EvaluationHow 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 ObjectivesBy 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

AimTo show the effect of yeast on dough

MethodWeigh 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

ResultsTime(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

AnalysisDraw one line graph to show both sets of results

Height of dough (mm)

Time (Minutes)

ConclusionWhat conclusion can be drawn from the results?Yeast causes the dough to rise

What is varied in this experiment?Only the presence of yeast

What steps are taken to make this experiment Reliable, Accurate and Valid?

Same mass of flour and sugarSame volume of liquidKept at the same temperatureLeft for the same time

Evaluation

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

IntroductionAntibiotics are chemicals which can ______________

____________________Many antibiotics are produced by fungi.Discs of paper can be soaked in different

antibiotics and different strengths (concentrations of antibiotics)

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.

Prevent the growth or killbacteria

Nutrient agar in a petri dish

AimTo show the effect of different antibiotics on the

growth of a bacterium

Method1. 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 ConclusionWhat 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?

Penicillin _____________ the growth of the bacterium.

What is the effect of streptomycin on the bacterium?

Streptomycin ___________ the growth of the bacterium

INHIBITS

has no effect on

EvaluationWhat 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

IntroductionWhen milk is kept at a warm temperature

___________________________ and turn it _________ _______________________

Some types of bacteria will do this and ___________________________________

UHT milk has been _____________________________ __________ it is sterile

Bacteria will start to grow “sour”

Because of acid production

Turn the milk into yoghurt

Heated to high temperatures to kill all the Bacteria,

Aim

To show acid production by the action of yoghurt bacteria on milk

Method1. Add 10cm3 of UHT milk into each of two

clean test tubes labelled A and B2. Add 1cm3 of yoghurt bacteria to tube A and

1cm3 of sterile water to tube B3. Incubate the tubes at 30oc for 24 hours4. Examine the tubes and record the

appearance in your results table5. Test the pH of each tube with universal

indicator and record your result.

Results

Tube Appearance pH

A

B

Conclusion

The bacteria cause the pH to fall, become more acid

• What is the effect of the bacteria on the pH of the milk?

EvaluationHow 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