Proteins : Tube Solution/food Color reaction to Biuret Reagent Presence of prote
ID: 6875 • Letter: P
Question
Proteins:
Tube
Solution/food
Color reaction to Biuret Reagent
Presence of protein (violet color)
1
2ml distilled water
No change
no
2
2ml milk
Purple
Yes
3
2ml egg white
Purple
yes
4
2ml egg yolk
No change
no
5
2ml honey
No change
no
Did any of the foods/solutions that tested positive for protein also test
positive for reducing sugars (Benedicts Test) or starch (Iodine test)? Explain your answer.
Tube
Solution/food
Color reaction to Biuret Reagent
Presence of protein (violet color)
1
2ml distilled water
No change
no
2
2ml milk
Purple
Yes
3
2ml egg white
Purple
yes
4
2ml egg yolk
No change
no
5
2ml honey
No change
no
Explanation / Answer
I'm not exactly sure what you mean by animal sources, but if you look at your data, out of the five variables, only milk and egg white tested positive for protein. Water will not test positive for any of the reagent tests because there are no free OH groups to react with the copper ions in Benedict’s Reagent for reducing sugars, no peptide bonds to react with the copper ions in Biuret’s Reagent for proteins, and no coiled chains trapping iodine for starch. Milk will not contain any starch but does contain reducing sugars (because the anomeric carbon of glucose in lactose has a free OH group to react with Benedict’s solution) and proteins (because whole milk contains proteins with peptide bonds that react with the copper ions in the Biuret’s reagent causing the solution to turn violet). Since you did not give the data for the other three results, I cannot deduce if there are/are not reducing sugars or protein in them. However, if you have the results on hand, you can use the explanations from above and deduce answers for the other three. I hope this helped you.
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