Resources

LT-F2.4

ISE 5-14 Curriculum Support Materials                                                           Overview advice

Group 33 exemplar Living things & the processes of life - Cells (Word)

It is best to use an experiment which the pupils are familiar with and demonstrate the effect of temperature and pH.

Mindmap example - Cells (thanks to George Milne)

Using egg white in capillary tubing has the advantage that it is readily visible and can be measured can be made with some degree of accuracy.

Skills related to problem solving and practical applications should be developed.

Starting Science - SO-7.4
Spotlight Science - 27d

Pectinases are enzymes that break down the polysaccharide pectin which is located primarily in the middle of cell walls in e.g. the tissues of fruits. They are large molecules which are responsible for holding particles in suspension in fruit juices. They also increase the viscosity (runniness) of the juice. In tomato and orange juice suspended particles is OK to most people. However, they prefer the "bits" to be removed in “clear” juices such as apple and grape. To produce clear apple juice it is necessary to remove the pectin from it. Pectin forms a colloidal solution in water and gels on cooling. When fruits are cooked with the correct amount of sugar, and when the acidity is optimum and the amount of Pectin present is sufficient, jams and jellies can be made. Commercially prepared pectinase can be added to prepared fruits in order to hasten the release of juice and aid in the “settling out” of suspended particles in fruit juice, cider and wines. The insoluble solids that settle down to the bottom of the container can be filtered out or the clear liquid from the top siphoned off, leaving the undesirable precipitates in a sludge on the bottom. In wine-making, this is called "racking." See a pdf file on the production of apple juice.

Experiment from the Scitech Forums at UCLan - Making apple juice
Dilute the Pectinase with an equal volume of water just before using.
Chop 1 medium sized apple into small pieces, split into 2 beakers.
Add 2 cm³ of diluted Pectinase to 1 beaker and 2 cm³ water to the other.
Incubate at 40 deg. C 15-20 mins.
Filter the juice and record the volume of juice obtained.
Use different apples to see the difference in 'juiciness' of various apples.

An extra activity is: Does the addition of Cellulase to the pulp enhance the yield of juice? Do Pectinase and Cellulase further enhance yields?
We have not done this yet, but I should imagine that the dilution of Cellulase is the same as for Pectinase....I can't find the details in the instructions!

It is amazing how different apples types and ages yield differently.

Mandy Evans - Leeds Metropolitan University