PP-1-using Biochemical Tests to Identify Carbohydrates And Protein Flashcards
What does Benedict’s test test for?
Reducing sugars
Outline how Benedict’s test is carried out
A substance is mixed with Benedict’s reagent and heated in a water bath
Outline the colour change in Benedict’s test
Blue- Green- Yellow - Orange - Brick Red PPT
Why is Benedict’s test described as semi-quantitative?
It can only estimate a quantity of reducing sugars
How can a Non-reducing sugar be identified through Benedict’s test?
A non reducing sugar is hydrolysed into its monosaccharides with dilute HCl
Why is the clinistix test useful? How is it carried out?
It can test for glucose ( therefore distinguishing it from other reducing sugars )
It’s also a useful way for doctors to test for signs of diabetes ( glucose in the urine )
A strip is dipped into a test solution, it will change colour in presence of glucose
Colour change in iodine test
Yellow-Brown to blue-black
What does the biuret test test for?
Proteins/ Polypeptide bonds
Outline the biuret test
Add equal volumes of potassium hydroxide to a test sample then add 2-3 drops of dilute copper sulfate solution then shake.
Results of biuret test
Blue - lilac
How would you test solid foods?
Grind into a paste ( add water if necessary )
How can you test if a substance has both reducing and non-reducing sugars.
Initial Benedict’s test will give a colour change
After hydrolysis and redoing Benedict’s the colour change will be further along proving there is now more reducing sugars.
