Download 1. Sucrose is a disaccharide. It is formed from two

1.
Sucrose is a disaccharide. It is formed from two monosaccharides P and Q.
The diagram shows the structure of molecules of sucrose and monosaccharide P.
CH 2 OH
O
H
H
OH
H
O
OH
H
O
CH 2 OH
H
OH
H
H
HO
CH 2 OH
OH
H
Sucrose
CH 2 OH
O
H
H
OH
H
OH
Monosaccharide P
(i)
+
H
OH
(a)
H
OH
Monosaccharide Q
Name monosaccharide Q.
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(1)
(ii)
Draw the structure of a molecule of monosaccharide Q in the space above.
(1)
(b)
The enzyme sucrase catalyses the breakdown of sucrose into monosaccharides.
What type of reaction is this breakdown?
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(1)
The Queen Katherine School
1
(c)
The diagram shows apparatus used in breaking down sucrose. The enzyme sucrase
is fixed to inert beads. Sucrose solution is then passed through the column.
Sucrose solution
Sucrase fixed
to beads
Gauze
Products
Describe a biochemical test to find out if the solution collected from the apparatus
contains
(i)
the products;
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(2)
(ii)
the enzyme.
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(2)
(Total 7 marks)
The Queen Katherine School
2
2.
The table shows the number of carbon atoms contained in some substances.
Substance
Number of carbon atoms
Amino acid
2 - 11
Glycerol
Glucose
6
Pyruvate
Starch
(a)
Large and variable number
Complete the table to show the number of carbon atoms in glycerol and pyruvate.
(2)
(b)
Explain why the number of carbon atoms
(i)
may vary from 2 to 11 in an amino acid molecule;
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(1)
(ii)
may be described as variable in a starch molecule.
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(1)
(c)
Explain why the type of chemical reaction in which glucose is converted to starch may be
described as condensation.
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(2)
(Total 6 marks)
The Queen Katherine School
3