Carbohydrates
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Q1.
Lactose is a disaccharide found in milk. In the human small intestine, the enzyme lactase
catalyses the hydrolysis of lactose to the monosaccharides, galactose and glucose. These
monosaccharides are then absorbed into the blood.
(a) Complete the diagram to show the hydrolysis of lactose to galactose and glucose.
*
Ho
O
1
H
Ho
H+
Ho
H
Heo
OH
1,
0
(2)
(b)
Starch and protein are biologically important polymers. Explain what is meant by a
polymer.
long repeating
A
______________________________________________________________
chains at monomers
polymer is a molecule made up of
.
______________________________________________________________
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0
(1)
•
(Total 3 marks)
Q2.
Scientists investigated the hydrolysis of cellulose from samples taken from recycled paper.
They measured the concentration of the products formed in the reaction.
(a)
Name the monomer that forms a cellulose molecule.
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b___________________________________________________________________
glucose
(b)
(1)
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Describe a biochemical test for the monomer you named in your answer to question (a).
test
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☐ addicts
reagent
:
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Add 2cm A food sample
1)___________________________________________________________________
]
Add equal amount of Bwdicti
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2)
reagent
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3) place in hot water bath for 5 minutes
'
.
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7) If color becomes : green yellow, orange or rod then it is found
,
.
,
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0
(2)
(c)
In the investigation, the scientists mix the enzyme cellulase with the paper and a buffer
solution in an incubated flask.
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To measure
the progress of the hydrolysis reaction, samples are taken from the flask
every twelve hours.
The concentration of the products in each sample is measured.
The table shows the scientists’ results.
62.5
-
61.8
(72×60)-(-6-1160)
=a?
(d)
Hours
Concentration of
products / g dm 3
12
24
36
48
60
72
28.2
42.9
55.7
59.2
61.8
62.5
Rate of hydrolysis of
cellulose / g dm 3
minutes 1
39.2 × 10–3
20.4 × 10–3
17.8 × 10–3
4.9 × 10–3
3.6 × 10–3
Calculate the missing rate of hydrolysis. Write your answer in the table.
Plot a suitable graph of the rates of hydrolysis as shown in the table.
I(1)
To
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12
(e)
24
48
36
①
72
60
Hours
(3)
Describe and explain the results of this investigation.
Tk
___________________________________________________________________
more time that passes the
higher the concentration of products this
,
___________________________________________________________________
molecules into smaller products Another
is
becase d hydrolysis turning
larger
.
___________________________________________________________________
the time tie lower the rated hydrolysis is This is
thing is that the
longer
.
be
___________________________________________________________________
case the amount A large molecules that can be hydrolink is
decreasing
,
___________________________________________________________________
meaning four things can be hydro libel steep decrease and then a less rapid
•
.
___________________________________________________________________
decrease
amount A
High initial rate d reaction at 12 hours as a
large
.
cellulose Decreased rate A Nation be case more cellulose was hydrolysed few cellulose left
___________________________________________________________________
.
y
,
(3)
(f)
Explain how the structure of cellulose is related to its role in plant cell walls.
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cellulose is used to keep the plants structure
___________________________________________________________________
rigid it forms mic roti birds
,
strong
that
___________________________________________________________________
are connected with
strong hydrogen bonds These micrdi birds are very
.
and
___________________________________________________________________
insoluble
strong molecules to hold the structure
making great
•
Attendant
Forms long wnbrancek chains CN B- glucose)
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
2
___________________________________________________________________
,
(3)
(Total 13 marks)
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