Science Buddies: "Ask an Expert"

I want to do something with the enzyme pepsin, and from the research I have done I've learned that pepsin breaks down proteins into smaller units called peptides, and then the peptides are then absorbed from the intestine into the bloodstream. I want to test to see which homemade protein bar will break down the slowest to keep a person full till their next meal. I'm planning on making different types of protein bars with different types of nuts. But I am having a hard time figuring out how much pepsin and HCl solution is needed to preform the experiment. I also read that a spectrometer can be used to test the rate of reaction because when a enzyme is mixed with it's substrate it produces a color. Can I use this to collect data from project I want to do?

Hi Haleylove,

That sounds like an interesting project!

In terms of the correct amount of HCl and pepsin to use, think about the conditions in which the enzyme normally works in our body (ie in the digestive system). http://oureverydaylife.com/optimum-ph-h ... 33086.html
You would want to make sure that pepsin was working in the optimal pH conditions, and you would control that using HCl.

There are some good resources in terms of using pepsin to digest egg whites, and it might serve as a good starting point.
http://science.jburroughs.org/resources ... Teach2.pdf

This one talks about using the spectrophotometric assay. https://www.youtube.com/watch?v=VuOVzCx3yF8

Also you might want to think about the Biuret assay, which is a colormetric assay and might be easier.
It measures how much proteins have broken down.
https://www.youtube.com/watch?v=bi2LtNh5h50

Hope this helps,

Elizabeth