Tube Number 1 2 3 4 5 6 7 8 9 10 Absorbance at 510nm 0.337 0.131 0.202 0.139 0.1
ID: 272758 • Letter: T
Question
Tube Number
1
2
3
4
5
6
7
8
9
10
Absorbance at 510nm
0.337
0.131
0.202
0.139
0.140
0.235
0.251
0.402
0.4420
0
Glucose conc (ug ml-1)
(Estimate from your standard curve)
20
50
100
150
200
Unknown B
tube number 1-4 is the hydrolysate
tube number 5-9 is standards
tube 10 is the blank
Question1)a). Could the purity of cellulose be estimated using the same method, acid hydrolysis, as used to estimate the purity of glycogen using these results above? (no more than 100 words; use
key words)
Yes No
(1 mark)
b)You are given a drink that you are told is sweetened with either maltose or lactose. Using the following resources explain how you would test if the drink was sweetened with either lactose or maltose? Explain the carbohydrate chemistry behind the test to justify your answer.
The only (!) resources available to you include:
the drink
the enzyme lactase
the Somogyi-Nelson reagents for the determination of reducing sugars.
(2 marks)
i) concisely describe the tests that you would use:
(1.0 marks)
ii) describe the observations that would be made if the drink contained maltose:
(0.5 marks)
iii) describe the observations that would be made if the drink contained lactose
(0.5 marks)
Tube Number
1
2
3
4
5
6
7
8
9
10
Absorbance at 510nm
0.337
0.131
0.202
0.139
0.140
0.235
0.251
0.402
0.4420
0
Glucose conc (ug ml-1)
(Estimate from your standard curve)
20
50
100
150
200
Unknown B
Explanation / Answer
1. a) Yes the purity of cellulose can also be estimated using the acid hydrolysis method. As, cellulose hydrolyses into glucose units by heating cellulose to high temperatures in the presence of concentrated mineral acids.
b) maltose is a dissacharide, made up of two glucose residues, joined by an alpha1-4 glycosidic bond
Whereas, lactose is a dissacharide consisting of glucose and galactose residues.
when lactose is treated with lactase, it will be hydrolysed into the reducing sugars, glucose and galactose whereas maltose will remain unaffected. Hydrolysing lactose with lactase and then heating it with Somogyi-Nelson reagent, will give a blue coloration of high intensity due to presence of high amount of reducing sugar, whereas maltose will remain unaffected and will produce a blue color of less intensity on treatment with Somogyi-Nelson reagent.
i) reducing sugars, when heated with alkaline copper tartrate, reduces it to cuprous ions that forms cuprous oxide which reacts with arsenomolybdate to form a blue colored complex with an absorption maxima at 520nm.
ii) maltose is a reducing sugar, it will give positive Somogyi-Nelson test and will produce a blue color.
iii) lactose is also a reducing sugar and will produce a blue coloration with Somogyi-Nelson reagent.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.