Sucrose and Glucose in ten Foods, and Invertase Action

[deleted-131870]

I'm doing a science project with three other group members for a class activity, and we are using the procedure in the "Sucrose & Glucose & Fructose, Oh My! Uncovering Hidden Sugar in Your Food" project, found on https://www.sciencebuddies.org/science- ... #procedure. We have a few questions on our project:

1. In the second part of our experiment, we used a 10% sucrose (and water) solution to test invertase activity. We added .6 mL of invertase to the solution, and over the course of time the sucrose was broken into glucose in a linear relationship, until the invertase activity stopped, and the concentration of glucose leveled out to about 5%. Is the other 5% of the original 10% sucrose solution fructose, or did some sucrose just not break down completely?

2. Why do ketones in the test sample affect color development when testing with glucose strips?

3. Does pH affect invertase activity?


Also, it would be great if somebody could reply ASAP because this project is due really soon!
Thank you so much!

-Erica, Aarya, Louisa, Christine

[deleted-63393]

Hello Erica and friends,
For your first question, I think it would be helpful for you to google the chemical structure of both sucrose and glucose. This will help you to determine if the molecules have the same amount of chemical elements in them. My guess for why the glucose solution is a lower percentage is that it may be a bigger molecule than the sucrose molecule. For example, sucrose may contain two carbon molecules C-C and glucose may contain 4 C-C-C-C. To be sure, you will need to find out the chemical structure for each. If they are the same size, then yes...it may be that you didnt' have enough enzyme of invertase to convert all of the sucrose.

Ketones also have a different chemical structure to them. I would determine what it is in addition to the sugars. My guess is that it has some nitrogen in it's chemical structure which can cause a change in pH. This could be the reason for the color change. Again, you can verify this by looking online.

In regards to pH affecting invertase activity? My guess would be yes. Most enzymes only work under certain conditions. To confirm this you again would need to know the chemical structure of the enzyme. Determine what molecule whether it be nitrogen, sodium, etc would be causing the pH change and then determine if that molecule would interfere with the ezyme's ability to break apart sugar. This is getting it some serious organic chemistry so it may be beyond what you want to try and tackle for your experiment. I think you could make some basic assumptions by finding out just a bit more information about enzymes and their preferred environment in general. You may be able to find this information just by searching on google.

Hope this helps!
Katie

[deleted-131870]

Thanks for taking the time to answer our questions!

I have come to the assumption that the reason why, after testing, 10% sucrose solution became a 5% glucose solution - sucrose is made of a glucose molecule and a fructose molecule, therefore the other 5% is fructose, which was not tested for. However this hasn't affected our experiment, just brought up more questions:

Does honey, syrup, and coca-cola have more glucose, fructose, or sucrose in them?
How about squash, sweet potatoes, and pears?
Lastly, how about green tea, milk, and soy milk?

On the other hand, we will come to the topic of pH affecting the enzymes' job in our analysis of results, and come to conclusions about whether they affect them or not.

Thanks again!


--Erica