Edexcel Biology CP2 Enzymes and pH

Hi all
Edexcel GCSE biology core practical 2 looking at enzymes and pH

What concentration amylase and starch solution works best? I'm going to trial it tomorrow but want to have a starting point. The sheet says it should take around 60 seconds at pH 7, however when I spoke to one of the teachers she said last year they struggled to get results because it happened almost instantly (old technician - I don't know what concentration she used).

Thank you. If no responses I'll report back with what works for me.
 
Using liquid amylase, I'd use between 1%-0.25% - probably nearer 0.25% than 1% if its not a really cold day, or you are using water baths to warm the whole lot. 1% starch, but take that down to 0.5% if you want to speed things up. You don't want it to go too fast otherwise they won't have time to see a change. It will also depend slightly on the age of your amylase - its suggested to only keep it for 1 year in the fridge - mine is about 5 years old and still pretty active though!
 
The core practical is CB1g and this is the lablogger template for this - We use powdered pancreatin so you will find that pancreatic amylase works best in alkaline conditions
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Ran the temperature one CB1f1 this morning using 5ml 0.1% pancreatin and 5ml 2% starch (I use 'soluble' starch and heat it until it goes clear, that way the starch molecules don't settle out and stay in solution). Room temperature took 6.5 minutes to remove all the starch. I guess the pH would be that of the panceatin - slightly alkaline,
 
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I've used past 2 days 0.5% Amylase & 1% starch. worked a treat last 2 lessons, all satisfied. ( really depends on the Amylase, supplier etc, sometimes we use much weaker solutions if it's the good stuff)
Tried 1% Amylase but 1 teacher said was too quick, next teacher said too slow, some said didn't work at all :rolleyes:
I don't go by my own results as once it goes through that classroom door anything can happen! ( I test it myself but honestly the child factor has to be accounted for)
I also label top of all syringes with 'S' for starch. 'A' for Amylase & put them out with each solution to prevent contamination. Also use different sized beakers for S & A. anything to cut chance of mix up's.
We use Buffers 3-8.
Making starch. We do it a different way to Peter. Weigh starch, put into a beaker with a little distilled just to make runny paste, put in enough boiling distilled until it's clear. Then top up to required amount with cold distilled.
 

karen b

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Making starch. We do it a different way to Peter. Weigh starch, put into a beaker with a little distilled just to make runny paste, put in enough boiling distilled until it's clear. Then top up to required amount with cold distilled.
We use this method too
 
Apparently resistant starch in food is not digested in the small intestine
I get the idea of resistant starch being types of starch which are harder to digest because of their chain lengths and configuration - it's the chilling starch in the fridge changing it somehow I don't get
 
I get the idea of resistant starch being types of starch which are harder to digest because of their chain lengths and configuration - it's the chilling starch in the fridge changing it somehow I don't get
If you chill food or freeze bread some of the starch becomes resistant (I presume to the amylase enzymes) even if you reheat it.

If cooking includes excess water, the starch is gelatinized and becomes more digestible. However, if these starch gels are then cooled, they can form starch crystals resistant to digestive enzymes (Type RS3 or retrograded resistant starch),[8] such as those occurring in cooked and cooled cereals or potatoes (e.g., potato salad).[33][34] Cooling a boiled potato overnight increases the amount of resistant starch.[35]
https://en.wikipedia.org/wiki/Resis...starch,manufactured types of resistant starch.
 
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