reducing and non-reducing sugars

Question 1

what is a reducing sugar ?

give examples

Answer 1

-sugar that can donate an electron to another molecule

-all monosaccharides
-some disaccharides: maltose and lactose

Question 2

what is a non reducing sugar?

give an example

Answer 2

-sugar that can’t donate an electron

-some disaccharides: sucrose

Question 3

what is the test for starch?

Answer 3

1. add iodine
2. positive test: from orange to blue/black

Question 4

explain the test for reducing sugars

Answer 4

1. add benedict’s reagent then boil in water bath
2. positive test from blue to green to yellow to orange to brick red

-reducing sugars add an electron to copper ions in benedict = forms red precipitate
-semi quantitative

Question 5

explain the test for non-reducing sugar

Answer 5

1.following a negative benedict’s test (stayed blue)
2.add HCL acid and heat in water bath = hydrolyse glycosidic bonds releasing the monosaccharides
3.add dilute alkali (sodium carbonate)to neutralise
4. add benedict’s solution and heat in water bath
5.positive: brick red