help please -enzyme prac to demonstrate substrate conc?

[Ocean Breeze]

Teacher would like
an enzyme prac to demonstrate the effect of substrate concentration.

Has been using milk and rennin, but its not really very effective at identifying an end point

Was thinking maybe something with amalase or lipase?

heres hoping that you clever people have something up your sleeve

(oops.. I edited cause I am an idiot!)

[bindibadgi]

The catalase prac using capsicum & H2O2 works nicely with H2O2 conc as the variable.

Because it comes as a 6% solution, you can easily do dilutions of 1%-5%. Our kids get mostly good results, unless of course they do something unexpectedly stoopid

[Rowyrow]

something unexpectedly stoopid

hahahhaaaaaaa the stoopidness is expected here

[Ocean Breeze]

bindibadgi

I dont know that prac.. can you post it here please?

R-S

[bindibadgi]

Here's our prac method.

Capsicum Catalase Prac Method.docx

The capsicum prac was originally posted here on Chemtalk by the wonderful Sassi
We now do it as a major summative prac with our Yr 12 Biology classes & it works beautifully, & makes the labs smell like a fresh salad instead of the stinky liver version we did before discovering the capsicum one.....all hail Sassi!!

To make the capsicum extract chop up green capsicum & blend it in a food processor till it's a thick puree.
Then filter it through a couple of chux cloths inside a large funnel, & squeeze the chux to get the last of the juice out.
You'll have a lovely bright green extract. I get about 50ml per capsicum. Call that your 100% & dilute down.
I make the extract a little while before they need it, & then do a quick test run to make sure the reaction isn't too vigorous or too wussy.
If the foam charges up the 50ml measuring cylinder & out the top so you can't get a reading, dilute the extract a little & test again, or shorten the time.
You're aiming for a foam height between 40-50ml with 100% capsicum & 6% H2O2.

[rae]

These pracs also work using either silverbeet/spinach or potato as the source of catalase and the 6% peroxide as the substrate.

[dime]

We use potatoes and use old cork borers to get the same amount for each one. Then vary the peroxide strength, pH and temp to get the desired results. Bio teacher is very happy with the results.

[Ocean Breeze]

Thanks so much for the prac Bindibadgi:) and the potato & silver beet ones? anyone have those as well??
I have never ever done the liver one, as I could not face the cleaning up afterwards!

[RosalieM]

Quick question - we only want to test one type of capsicum changing the concentration of H2O2. What colour capsicum should I buy? we are doing it on Monday for the first time. I've been waiting since Sassi posted it for a chance to give it a go!

[bindibadgi]

Green has the highest level of catalase.....a fun extension to do is test the different coloured capsicums, if you're lucky you can find purple & orange as well as the usual red & yellow.
I'm sure google would tell you the levels in each colour, & someone once posted that red is ripened green, & I think yellow is a hybrid?

[Ocean Breeze]

thats very interesting.
I shall just buy the green ..dont want to get too fancy to start with

[RosalieM]

Thanks. I'll stock up on some green capsicums for Monday I just did a trial run. It is being used as a prac exam so I guess the kids get to decide how much of each they will use. Turns out they are testing the effect of temperature, not concentration, so it will be interesting to see what happens.

[Ocean Breeze]

My teacher want to know ( re the green capsicum prac).. are the different concentrations measurable ( rather than merely subjective)?

[smiley]

Ummm. Aren't you altering the concentrations of the Hydrogen Peroxide, and therefore they are eminently measurable, because you're controlling them? And the results can be made measurable by volume, if you do the testing in a measuring cylinder, because the foam with rise to whatever level in the cylinder, thus indicating a volume per se.

[bindibadgi]

Ditto what Smiley said......the H2O2 conc is known (we use 6%) so you calculate your dilutions from that.
We dilute 5%-0%.
We call our capsicum extract our "100%" & then dilute down as needed.
We usually dilute to 80%, 60%, 40%, 20%, 0%
If you do the prac in 50ml measuring cylinders you can measure the volume of foam produced in the given time limit, eg 30 secs.

[RosalieM]

OK it's capsicum prac time again!! Just wondering if the capsicum extract will survive overnight if I blend it all up today? I want to make sure it works but won't have time to check it tomorrow then go get more capsicums if it's no good...

[fibreweb]

Ours did not seem to keep it's full strength overnight (but then we used spinach which works very well when it is fresh)

How about just pureeing up a very small amount to check it today and doing the rest tomorrow.

Wendy

[RosalieM]

Thanks Wendy. I'll just leave it till tomorrow. It SHOULD work The prac exam is P3&4. I'll just make sure I have absolutely everything else out and done this arvo so I can get the extract right in the morning. I'm too lazy to clean the blender twice!!

[matchstick]

why are you doing prac exams in term 4?

[RosalieM]

It's for year 11 going into yr 12 so they are already doing their yr 12 work.