The Effect of pH on the Digestion of Casein by Trypsin

The Effect of pH on the Digestion of Casein by Trypsin

When planning the experiment, the equipment and method had to be well

thought-out in order for the experiment to be accurate and efficient.

Firstly, I have chose to use a 1% trypsin concentration then altered

it to 0.8%, because a higher concentration means more trypsin

molecules in the solution and therefore more enzyme substrate

complexes are likely to occur with the casein in the milk, causing

digestion of the casein to be faster. However, I don’t wantowever

digestion to occur too quickly as I will not be able to analyse the

effect of PH. Therefore, I chose a lower concentration which would

allow me to test the percentage transmission at different PH.

Enzymes are proteins that act as catalysts to speed up reactions

without being used up. However, I will use a higher amount of enzyme

than substrate as although it is reusable, the reaction will proceed

at its maximum rate and the enzyme will not be the limiting factor.

The use of digital scales would provide more accuracy as you can

obtain measurements of to up several decimal places.

Skim-milk will be used rather than whole milk because skim-milk

provides more protein and therefore more casein in the experiment.

The effect of a change in PH on enzymes is the alteration in the ionic

charge of amino acids at the active site, so the active site changes

and the enzyme can no longer form enzyme-substrate complexes. To test

the effect of various PH on the digestion of casein I decided to use

PH 4, PH7 and PH9.5 because I could then, compare the effect of acidic

neutral and alkaline conditions on the digestion catalysed by tr...

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...ke-up experimental time and may take different

times for each, therefore shaking all the test-tubes will ensure that

the reagents are mixed initially.

I intended to use immobilized enzymes as they would be easy to remove

in order to stop the reaction i.e. Alginate beads which can be sieved.

However we know that immobilization may lead to loss of enzymatic

activity e.g. due to the immobilizing framework hindering the arrival

of substrates into the active site. Therefore, when removing the

test-tubes from the water bath and placing solutions in the

colorimeter, I will have to work quickly as immobilized enzymes won’t

be used and the reaction will not be stopped.

Finally repeating the experiment thirty times would allow better

evaluation of the experiment and provide sufficient data to carry out

statistical tests.