Monday 20 March 2017
Revision Test: Biological Molecules
1. The diagram below shows the structure of a molecule found in the cell surface
membrane.
A B
Fatty acid
Fatty acid
Phosphate
Region X
(a) Name the type of molecule shown in the diagram.
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(b) Name A and B as labelled on the diagram.
A _______________________________________________________ [1]
B _______________________________________________________ [1]
(c) Region X is said to be hydrophobic. What is meant by the term hydrophobic?
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(d) Explain why the cell surface membrane is described as a fluid-mosaic.
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[Total: 6 marks]
2. The diagram below shows the structure of a triglyceride molecule.
H O
H C O C
O
H C O C
O
H C O C
H
(a) (i) Name the part of the molecule labelled A.
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(ii) Name the type of bond formed between part A and a fatty acid.
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(b) Stearic acid and oleic acid are both examples of fatty acids. Each has a
hydrocarbon chain containing 17 carbon atoms. Stearic acid is a saturated fatty
acid but oleic acid is an unsaturated fatty acid.
Give two ways in which the structure of a stearic acid molecule differs from the
structure of an oleic acid molecule.
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2. ___________________________________________________________
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(c) Describe two functions of lipids in animals.
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2. ___________________________________________________________
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3. The statements in the table below refer to three polysaccharide molecules.
If the statement is correct place a tick ( ) in the appropriate box and if the statement
is incorrect place a cross (X) in the appropriate box.
Statement Starch Glycogen Cellulose
Polymer of –
glucose
Glycosidic bonds
present
Unbranched chains
only
Energy store in
animal cells
[Total: 6 marks]
4. The information in the table below refers to some carbohydrates and their
roles in living organisms.
Complete the table by writing the name of the carbohydrate, or one role, in each of
the empty boxes.
Carbohydrate One role in living organisms
Form in which carbohydrate is transported in
mammals
Sucrose
Form in which carbohydrate is stored in mammals
Cellulose
[Total: 4 marks]
5. (b) Outline the molecular structure of starch [8]
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(b) Explain how the molecular structure of triglycerides is related to their functions. [8]
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