Explanation of results to unknown liquids practical

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Result to Benedict's test (reducing sugars)
Comment
A Glucose
+
As expected: glucose is a reducing sugar - proving Benedict's reagent and heating technique successful
B Liquid X
-
Not a reducing sugar
C Liquid Y
-
Not a reducing sugar
D X + Y incubated together
+
Reducing sugar produced by the action of X on Y (or Y on X)
E X [heat treated] + Y incubated together
-
Heat-treating X has an effect: stopping reaction probably an enzyme (protein denatured)
F X + Y [heat treated] incubated together
+
Heat-treating Y has no effect , so Y is not an enzyme. More likely to be a sugar.
From this:
X must be an enzyme.
Y must be a non-reducing sugar, which can be converted to reducing sugar(s).
The only common non-reducing sugar is sucrose.
The enzyme acting on it is sucrase (also known as invertase).