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. Aim To look at a variety of cells in order to identify cell structures 0.1 mm Stains

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

SpecimenStructures Visible StainPlant or Animal ReasonMagnifi cation Drawing Cheek Epithelium Cell Membrane Cytoplasm Nucleus Methylene Blue/ iodine solution AnimalNo cell wall present x200 Elodea Cell Wall Chloroplasts PlantCell wall present x100 Onion Epidermis Cell Wall Cytoplasm Nucleus Iodine Solution PlantCell wall present x100 Rhubarb Epidermis Cell Wall Vacuole PlantCell Wall present x100 Cell wall Vacuole

Conclusion Evaluation The cell wall, Cell membrane Cytoplasm Nucleus Chloroplast 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 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 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 ( o C) pHSmellLime water alcoholcloudy

Conclusion What is produced during fermentation as shown by the tests? TestProduct Smell Lime WaterTurned ___________ showing ____________________ was produced pHThe pH fell because ________________ is an acidic gas Temperature ( o C)Temperature _________ showing that ___________________ was produced What does this evidence support? The equation for alcoholic fermentation Ethanol/Alcohol cloudy Carbon dioxide increased Heat energy

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 20cm 3 of water into 1 beaker and 20cm 3 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 30 o C. START THE STOPCLOCK. Record the volume of the dough at 5minute intervals for 30mins

Results Time (minutes) Volume of dough without yeast (cm 3 ) Volume of dough with yeast (cm 3 )

Analysis Draw one line graph to show both sets of results Height of dough (mm) Time (Minutes)

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

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 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

Introduction Antibiotics 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 kill bacteria Nutrient agar in a petri dish

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? 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

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 ___________________________ 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

Method 1. Add 10cm 3 of UHT milk into each of two clean test tubes labelled A and B 2. Add 1cm 3 of yoghurt bacteria to tube A and 1cm 3 of sterile water to tube B 3. Incubate the tubes at 30 o c for 24 hours 4. Examine the tubes and record the appearance in your results table 5. Test the pH of each tube with universal indicator and record your result.

Results TubeAppearancepH 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?

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