2.3 Carbohydrates - Disaccharides & Polysaccharides Flashcards
Glucose linked to glucose forms
Maltose
Glucose linked to fructose forms
Sucrose
Glucose linked to galactose forms
Lactose
When monosaccharides form, a molecule of ? is removed
Water
When two monosaccharides join, it is what type of reaction?
Condensation
The bond between two monosaccharides is called a
Glycosidic bond
What happens when water is added to a disaccharide in stable conditions?
The glycosidic bond breaks and the two monosaccharides are released.
Define hydrolysis
Addition of water that causes a breakdown.
What must you first do before testing for non-reducing sugars?
Break it into its monosaccharide components by hydrolysis.
What is the procedure for testing for a non-reducing sugar?
First do the Benedict’s test, to be sure it isn’t a reducing sugar. Add another sample of the food to the same volume of HCl acid. This will hydrolyse the disaccharide into its monosaccharides. Slowly add sodium hydrogencarbonate and test pH to be sure it is alkaline. Repeat the Benedict’s test. If a non-reducing sugar was present, it will turn orange-brown.
Are polysaccharides soluble or insoluble?
Insoluble, as they are very large.
What is the test for starch?
Place the sample in a test tube, then add two drops of iodine solution and shake or stir.
In a test for starch, the sample will turn ? if starch is present.
Blue-black
What is the first step for testing for a non-reducing sugar?
Do the Benedict’s test, to be sure it isn’t a reducing sugar.
What is the second step for testing for a non-reducing sugar?
Add another sample of the food to the same volume of HCl acid. This will hydrolyse the disaccharide into its monosaccharides.
