Colorimitors and enzymes

Discussion in 'Supporting Biology' started by Jburns, Jan 14, 2020 at 12:43 PM.

  1. Hey guys,

    We are currently using Trypsin and powdered milk but we cannot get consistent results.

    So can anyone recommend share their method for doing this or can you recommended a different practical that uses enzymes of some sort with colorimeters?
     
  2. We use Protease at 1% and make up Marvel at 5%. These seems to work fairly consistently when the students test the effect of temperature on the speed of the reaction. i would have thought it should work similarly with Trypsin.
    How fresh is your Trypsin?
     
  3. I think that's Lipase and not Trypsin - different practical.
     
  4. We use 2% skimmed milk
    We then give out 1% Trypsin and the students do their dilutions and it takes about 25 mins for the weakest dilution to plateau out and about 10 mins for the strongest

    Not had a problem with that one in all the time we've done it - make sure you're using fresh Trypsin etc. and trail your Trypsin beforehand, might be you need different dilutions or better milk or something
     
  5. Until recently, only Marvel had a consistent formulation. Other varieties gave results all over the place. I'm not sure that Marvel is still as consistent as it used to be but you could try using that exclusively for a while to see if that works.
     
  6. Good point - I will see what I have for trypsin........but jburns also asked for other enzyme practicals that work in colorimeters
    Oops, now I have checked - have deleted the lipase one - it doesn't use colorimeters - sorry, doing things in a rush.
     
    Last edited: Jan 16, 2020 at 9:01 AM
  7. Hello, here are my Trypsin and Casein notes and results
     

    Attached Files:

  8. @Kiki thanks for that, do you think it would work well with a datalogger pH probe, and can it be used with a colorimeter? Also are you using casein powder or milk for your practical?

    @Cricketfool as long as its an enzyme and a data logger I don't think they mind really what they do. The enzyme turned up at the start of the term, it worked well in the trial and the first class that did it but we ran out of that milk powder and now the others we have tried have not worked. Also what's Marvel?

    Is that skimmed milk powder or just the milk from the bottle? We think its the milk that's the issue.
     
  9. Powder sorry
    Think we have the Sainsbury's one at the moment
     
  10. Hi Jburns, for the lipase prac we use real milk and for the trypsin prac we use Marvel milk powder. For the latter real milk doesn't work but for the former I haven't tried Marvel - I used full fat milk because it is a lipase experiment so wanted higher substrate ie- fat concentration. I haven't done any measurements with a pH probe.
     
  11. Also note that milk powders seem to eventually go off - I buy new in each year
     
  12. We have done with Asda milk powder and teachers were happy with the results
     
  13. use the cross method, are you trying AQA's colorimeter method, never had that work, the students are not fast enough and there are other ways of assessing that CPAC.
     
  14. If any enzyme, any substrate, then or Btech course uses benedicts for glucose concentration testing, presumably could easily use starch/amylase with starch/no amylase control?
     
  15. That's what we used and now our local one has stopped selling it, our pots use by date was 2017 but was working well. Just had to let it settle out then syphon off the good stuff. I will have a look for marvel milk powder.

    @clairelucas its for the OCR a level prac. But I will send my minions out to search the shops for marvel
     
  16. Marvel is skimmed milk powder available from most supermarkets.
     
  17. Tesco dried skimmed milk powder (Everyday value):)