Enzyme Prac that allows for variables in temp, pH and substr

[MariaC]

Does anyone have such a thing??? sick of trying experiments that don't perform as expected

[Ocker]

There is a lot of discussion on this prac Liver works best, chopped small or pureed.
Set up 3% peroxide in test tubes and place in water baths at 0C, 20C, 40C & 90C add liver /potato measure height of froth.
Repeat experiment with equal amounts of 0.1M HCl, Distilled water, & 0.1 NaOH add same amount 6% peroxide, add liver, measure height of froth.
Repeat eat expt. using 3%, 6%,& 12% peroxide, add liver, measure height of froth
I have 200 tall graduated test tubes that I keep for this prac.

[Ocker]

Yeah I cut liver into pieces about the size of a match head and push down with a stirring rod!

[rae]

Potatoes work well too!! Use a cork borer to get equal pieces.

[fibreweb]

Blended green capsicum or silverbeet works beautifully also.

You then can work on all liquid measurements rather then hoping bits are cut the same size.

Also much nicer to clean up.

[MariaC]

Thanks guys for all the replies, we are going with bought catalase versus blended capsicum to see which gives us better results

[bindibadgi]

Capsicum tends to be expensive these days, so I just puree a big 'ol bunch of spinach. Much cheaper & works a treat. Responds to temp & conc variation really nicely, but we haven't done pH. I think it would be fine though.
I've banned the use of liver but there's always one that will insist on doing it with an IB class, or a kid that wants to use it for an EE prac.

[fibreweb]

Spinach works beautifully for pH.

We use HCl at 0.05M which has a pH of about 2.42, HCl at 0.01M pH 4.34, tap water pH 6.4, NaOH 0.01M pH 9.03 and NaOH 0.05M pH 11.9.

I we found that a lot easier than trying to make the pH a specific figure as the basis of the experimint is to show the different reactions at various levels of pH. it doesn't matter if it is 4.34 or 4 or 5 etc.

We also found that doing the experiment in a 25 or 50 ml measuring cylinder worked extremely well as you could get a quantitative measurement of the amount of froth produced.

2 mls of 3% H2O2 5 ml of spinach "juice" and 3 mls of the acid or base.

[MariaC]

Hi Guys, I did a practice run yesterday, got great froth and desired results at differing temp, pH and concentration of hydrogen peroxide but went to fine tune today and so much less froth, so does this mean the capsicum extract is a use on the day scenario? cos its for period 1, of course! and lots of other stuff to do at the same time!!!! Really? I hear you all ask, a lab tech required to be in more than one place, doing more than one thing at once! MariaC

[annettegascoigne]

We use potato here too. And have a potato chipper that resides in the prep room for this prac. Seems to work well.

[Jazz]

image.jpg

THANK you to whoever posted fantastic recipe for enzyme (silver beet and peroxide)

[Ocker]

Hey if it works that well, goodbye to liver forever

[rae]

We have always have huge success with spinach. But I now have a new bio teacher and she has always done chicken liver so I'm nowb in the midst of trying to clean 120 boiling tubes with greasy chicken liver on them fun!! I must say though I had heard it was a smelly prac and I haven't experienced that at all.

[Lyn]

The smell is when you don't have the opportunity to clean up directly after the prac and you walk in next day to the smell of dead animal. Extracting rotting liver from measuring cylinders or test tubes is vile and time consuming.
You could point out to your new Bio teacher that there are far more hygienic methods, than liver, which are capable of producing excellent results.

[rae]

I did try. But she was determined!! I made the mistake of saying that sometimes you need to fiddle a bit with the spinach because it can be so concentrated. Need to learn not to be so honest. I really liked the potato prac too though! She won't be teaching them next year so I have a 2 year hiatus and then I may not be here!! LOL

[mtg]

Love this prac with my homegrown silverbeet, we just tested it against the capsicum and decided the silverbeet is better. When I remember the bad old days with the liver I have to thank chemtalk people again