Homework Sourse100 mM sucrose and 200 mM glucose equivalent starch solution
10.0 mM sucrose and 20.0 mM glucose equivalent starch solutions were hydrolysed in the presence of 4 M HCl or NaOH. Follow the preparation steps listed in your lab write-up to calculate the expected glucose equivalent concentration in the hydrolysates assuming, 90 % hydrolysis. (note you need to identify two dilution steps, and also consider how the hydrolysis affect the concentration of monosaccharides hence the glucose equivalent concentrations).
I. Hydrolysis of Sucrose and Starch by Acid and Base.
1)Label 4 test tubes “sucrose + HCl”, “sucrose + NaOH”, “starch + HCl”, “starch +NaOH”. NOTE: Be sure to place your tape labels near the top of the tubes so that they are not steamed off during the boiling step, or label the white area of the test tube with a pencil.
2)Place 2.00 ml of 6.0 mM sucrose into each of the 2 “sucrose” labeled test tubes, 2.00 ml of starch which has a concentration equivalent to 12 mM glucose into each of the 2 “starch” test tubes.
3)Add 2.00 ml of 4 M HCl to the tubes labeled “x + HCl” (x = sucrose, lactose or starch) and 2.00 ml of 4M NaOH in to the “x + NaOH” labeled tubes.
4)Place these tubes into a vigorously boiling water bath for 60 minutes (important!).
5)While the boiling is taking place set up 4 tubes, each containing 9.5 mL of 0.25 M K2HPO4. Label these 4 test tubes “sucrose + HCl”, “sucrose + NaOH, “starch + HCl”, “starch + NaOH”.
6)At the 60 min. point remove the tubes from the boiling water bath and pipet 0.50 ml from each of the boiled tubes into the corresponding tube with K2HPO4.
7)Take 0.5 ml of each of these 4 solutions and carry out the Nelson’s test as described below in procedure item 2.
Solution
Acid or base hydrolysis breaks polymer starch, and dimer sucrose into individual glucose molecules.
we have 10mM sucrose, which if 100% hydrolyzed would yield 20mM of Glucose.
Starch, if 100% hydrolyzed would yield 20mM of Glucose.
The test tubes were first diluted 10 times 2mL in 10 mL of 4M HCl or NaOH
Following dilution,
we have 10mM sucrose, which if 100% hydrolyzed would yield 2mM of Glucose.
Starch, if 100% hydrolyzed would yield 2mM of Glucose.
The efficiency of the acid or base hydrolysis was 90%. Thus,
we have 10mM sucrose, which if 100% hydrolyzed would yield 20mM of Glucose.
The hydrolysis of the starch would yield 20mM x 90/100 of Glucose.
= 18mM of Glucose
Similarly, hydrolysis of sucrose would yield 20mM x 90/100 of Glucose.
= 18mM of Glucose
For carrying out the Nelson test the Glucose would be further diluted 20x.
Therefore, the concentration would be:
0.9 mM in each test tube.
