investigating of factors affecting enzymes

[dolphinscales]

This year we have started using the QLD Sci Project book - a Heinemann book - " Biology a Contextual Approach" and in a few weeks doing the - investigating of factors affecting enzymes activity.
We have not done most of the suggested reactions but the teachers have gone with the effect of bromelain on protein - using gelatine and pepsin.
I was hoping to save me a lot of time is there any one out there in labbie land that do this reaction (or one of the others in the list) and if so any chance you would be willing to give me your method to play with - a starting point i guess.
PLEASE

cheers

[Whspa]

This is some information I've collected on enzymes.

1) Papain, from the latex of the papaya plant, is one of a family of plant enzymes that includes bromelin
(from pineapple) and ficin (from fig), all of which break down proteins. This is why the directions on
a box of Jello remind you never to use fresh or frozen pineapple in your gelatin, since gelatin is the
protein responsible for the “gel.” A convenient source of papain is fresh pineapple juice or meat
tenderizer.

Materials
Gelatin (Knox, Jello)
Beaker (150 ml)
Balance or teaspoon
Stirring rods (3)
Test tubes (2)
Test tube rack
Beaker of ice water
Hot plate
Distilled water (100 ml)

Procedure
1. Prepare a gelatin solution by heating 1 teaspoon (3.0 g) of gelatin in 100 ml distilled water until
dissolved. (Gently mix, do not boil.) Cool to room temperature.
2. Pour meat tenderizer into one of the two test tubes until it fills approximately 0.5 cm of the tube.
Label this tube as P. Do not put meat tenderizer in the other tube.
3. Fill each test tube 1/3 full (5 ml) with the gelatin solution. Mix gently.
4. Place tubes in ice water for 10 minutes.
5. Remove from ice bath and note the degree of gelatinization.

2) Fresh Pineapple Juice

3 test-tubes per group

100mLs of 10% gelatin (3 teaspoon of gelatin in 20mLs of cold water; add 80 mLs of hot water then mix)
Pour equal amount of gelatin in test-tubes
Test-tube 1: add 2mls of pineapple juice
Test-tube 2: add 2mls of pineapple juice then boil
Test-tube 3: add 2mls of water mix and set aside
Look at test-tubes after 15 min for results

3) Pepsin is an enzyme which aids in the breakdown of proteins and is secreted in the stomach of most
animals. It functions at a very low pH, which makes it ideal to use for studying the effect of pH on
enzyme activity. Commercial or natural albumin can be used as the protein source; however hardboiled
egg white is more impressive to demonstrate the action of pepsin.

Materials
Egg white (hard-boiled)
Test tubes (6)
Test tube rack
Solutions:
A: 1.0% Pepsin
B: Pepsin (1.0%) in 0.4% hydrochloric acid
C: 0.4% Hydrochloric acid
D: Pepsin (1.0%) in 0.5% sodium bicarbonate
E: 0.5% Sodium bicarbonate
F: Distilled water
Metric ruler
Knife

Procedure
1. Label test tubes A to F.
2. Fill each tube 1/3 full (5 ml) with the corresponding solution.
3. Drop a small (2 mm) cube of egg white into each tube.
4. Incubate at room temperature for approximately 12 hours. (The speed of this reaction can be
increased by using very thin strips of egg white and/or incubating at 30°C. Students might want
to compare the action of papain or bromelin under similar conditions.)
5. Examine tubes for the presence of the egg white.

Results
After 12 hours, the egg white will be “digested” in tube B; little, if any, of the cube will remain, while
there appears to be little change in the other tubes. If allowed to incubate longer, the cube in tube D
and possibly C will decrease in size.

[franco]

Hi Annette,

The attachment is the same prac as Whspa's Fresh Pineapple Juice, but with a bit more information.

Cheers,
Fran

[dolphinscales]

Many thanks for sharing ladies both very intersting and nicely set out and i will use it as a guide.

The teachers here are not using pineapple (costly and messey??!!) they intend to use geletine (sets) and various amounts of pepsin until the geletine does not set.

once again many thanks

[smiley]

I make ordinary jelly, or gelatin if you want to be boring, 90mL in a 100mL measuring cylinder. Make the jelly with slightly less water than recommended, especially in hot/humid places (e.g. Cairns, Darwin or the top half of WA). Blend fresh pineapple, or yes, even papaw, and add 10mL to the top of the set jelly. Put a marble in the cylinder. Note the time. Then time how long it takes for the marble to make it's way to the bottom of the cylinder.

The enzyme in the juice can only act on the surface area of the set jelly, so it usually takes a couple of hours to descend to the bottom of the tube.