Foundations in Biology Module 3.4 Testing for carbohydrates Flashcards
What chemical used to test the presence of reducing sugars
Benedict’s reagent
Define reduction
The gain of electrons
What does a reducing sugar do
They can donate electrons or reduce another molecule or chemical
What is the process for testing the presence of reducing sugars
- Place sample to be tested in a boiling tube
- Add equal volume of Benedict’s reagent
- Heat the mixture gently in a boiling water bath for 5 minutes
What do the reducing sugars react with
The Cu2+ ions in the Benedict’s reagent
What is the result in terms of ions of the test of reducing sugars
Cu2+ ions ( blue) are reduced by the addition of electrons to form Cu+ ions (brick red)
What is a positive test for testing for reducing sugars
Blue to brick red precipitate
Non-reducing sugars do not react with ………….
Benedict’s reagent
What is the most common example of a non-reducing sugar
Sucrose
What is the process of testing for non-reducing sugars
- Boil non-reducing sugar with hydrochloric acid
- Add equal volume of Benedict’s reagent
- Heat the mixture gently
When a positive test for non-reducing sugars happens, what is actually happening
Non-reducing sugar is hydrolysed by the acid
- sucrose = fructose and glucose which are reducing sugars
What does a positive test for non-reducing sugars look like
Blue to green/ yellow/ brown/ red
Depending on the concentration of the sugar
What is the chemical used in the test for starch
Iodine solution
What is the process of testing for starch
Few drops of iodine dissolved in potassium iodide is mixed with sample
What is a positive test for testing for starch
Orange/ brown = purple/black
