Carbohydrates - Monosaccharides

Question 1

How are carbohydrates constructed?

Answer 1

-Monosaccharides join together via condensation reactions (eliminating water molecules) to create polysaccharides.
-A ‘Polysaccharide’ is a carbohydrate.

Question 2

Describe the structure of a monosaccharide.

Answer 2

-Sweet-tasting and soluble
-General formula: (CH2O)n
-Examples include: glucose, galactose, fructose.
-Diagram on p.8 of alpha aned beta glucose.

Question 3

How is the Benedict’s test for reducing and non-reducing sugars carried out?

Answer 3

REDUCING:
-Add 2cm^3 of the food sample to be tested to a test tube.
-Add an equal volume of Benedict’s reagent (Copper II Sulfate).
-Heat the mixture in a gently boiling water for five minutes.
-Blue -> Green -> Yellow -> Orange -> Red (Positive result, based off of concentration)

NON-REDUCING:
-Perform the test for reducing sugars.
-Add another 2cm^3 of the food sample to 2cm^3 of dilute hydrochloric acid in a test tube and place the test tube in a boiling water bath for five minutes.
-Slowly add sodium hydrogencarbinate solution to the test tube in order to neutralise the hydrochloric acid (Test this with universal indicator paper).
-Re-test the solution with 2cm^3 of Benedict’s reagent.
-Orange-brown (Positive result)