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Hi all,
Can anyone help me?
We are about to do the enzyme pracs with H2O2 (pH, temp, substrate on liver and potato) but cant find anywhere the concentration of peroxide to use. I have a stock of 33% (I think) and know this is very strong.
Any ideas??

Hi!!
We are just doing these pracs now.
You need 3% H2O2.
We used silverbeet as one of our enzymes and this worked really well. Apparently the liver really smells if you use it!!
If you have access to the old web of life prac books it is in that. Also look at a previous post on Enzyme pracs from this week. There is an excellent website that I got information from.
Hope this helps!

Lorrae

We use 3% for most of these but 15% for a few of the experiments. Your teacher should know the % needed for the experiment.

That prac is also in the old Core Biology Prac book - Cells 1.16.

We haven't done that one for a while but I remember it worked well. The raw liver didn't smell but was pretty messy to clean up. The smelly part was boiling the liver for the comparison.

It also uses 3% H2O2 and MnO2 as the control.

Hope this helps

Some teachers leave things blank because they dont know themselves!!!!
Lucky they have us who bother and we have the Chemtalk family who have been such a great help and source of info!!!
Thank You CHEMTALK

Hi
We did the liver and peroxide test yesterday. Teacher was very happy with the prac. It worked well. We used 5%, 10% and 25% strength Hydrogen Peroxide.
Rita

My teacher did the prac this morning and just used the 6% peroxide straight from the bottle. She varied the pH and the temp but kept the concentration of H₂O₂ constant.

Ian

Hi!!
Our classes did this prac too but we also tried pepsin and egg white.
Has anyone else tried this? Did it work and what sort of results did you get? I'm wondering if our pepsin is still active as the only reaction was the enzyme, substrarte and basic pH.

Thanks
Lorrae

Hi All,
I've decided, after the past week spent refining and redoing the enzyme pracs, that this topic was invented to teach me the art of patience!!!! I've nutted out most of the problems, now we wait and see if the students can get it!!
I'm using pepsin with egg white suspension, catalase (potato cubes, liver stinks too much, and H2O2) and rennin(junket tablets or powder) with milk. We'll vary pH, temp and substrate concentration with all of them and.... fingers are crossed! I agree with Judy Miller (saliva prac thread), sometimes amylase is too tricky, and the thought of using human saliva turns even my strong stomach!
Regards
LIZ

Elizabeth,
Did you cook the egg first or did you use it raw?
How do you tell when it is digested??

Lorrae

Hi Rae,
I made an egg-white suspension by blending a hard-boiled egg white with 200mLs distilled water using a wand blender (Bamix type). Blend it for about 5mins and then filter it thru muslin a few times. When you add this to the pepsin the solution is sort of murky. As the egg white is "digested", the solution of egg and pepsin clears.
Liz

Elizabeth,

Thanks for the tip. I'll try that next time.

Lorrae

Lorrae, I like the sound of silverbeet, do you know what enzyme it contains?

Hey Bindi!

My understanding is that silverbeet contains catalase. We took a few leaves cut them up finely then put them in a blender with some water. The kids then strained off the juice and used this to react with the H2O2. It reacted very well with lots of froth and bubbles produced.
Hope this helps.
Lorrae

You can also use small pieces of potato in place of silverbeet - lotsa bubbles.
LIZ

We used the silverbeet for pH prac yesterday and it worked very well. Much less mess, no stink with lots of bubbles.

If anyone out there has a copy of the enzyme prac using spinach/silverbeet can they please fax me a copy. Fax: (08)89822203. Please put to the attention of the Laboratory Technician.
Thanks, Lyn.

Hi Lyn

If you have previously done the prac using potato discs or chunks, just chop up silverbeet leaves using a food processor or blender, strain the liquid and substitute about 1cm of this liquid instead of the potato bits. I'll fax you a copy from the office on the way out this arvo anyway.
Good luck
Julie

Thanks Julie. Fax received. I wasn't expecting so much useful info. It is all much appreciated.
Lyn.

The practical in the text I have stated 6% but I found we had some skin irritation with students from this. It is the only chemical I have come across to do this in any practical I have set up. I tried with 3% and it worked just as well with less risk, particularly for junior classes. If using higher concentrations students need to be particularly careful with use. I wonder if anyone else has come across this problem with H2O2?