AQA AS Biology
3.1 Biological Molecules
EXAM QUESTIONS BOOKLET
Use this booklet to revise for exams and improve exam
technique. Ensure you identify areas of strength and weakness
near exam time to make your revision effective, and use the
revision notes to fill in any gaps
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1
,1. The figure below represents a water molecule.
Water molecules are polar. As a result, they attract each other.
Draw a second water molecule on the figure above.
Your drawing should show:
• The bond(s) between the two molecules
• The name of the bond
• The charges on each atom.
[Total 3 marks]
2. Ponds provide a very stable environment for aquatic organisms. Three properties of water that
contribute to this stability are as follows:
● The density of water decreases as the temperature falls below 4°C, so ice floats on the top of the
pond.
● It acts as a solvent for ions such as nitrates (NO3–).
● A large quantity of energy is required to raise the temperature of water by 1°C.
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2
, Explain how these three properties help organisms survive in the pond.
In your answer you should make clear the links between the behaviour of the water molecules and
the survival of the organisms.
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[Total 8 marks]
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3
, 3. Water is important in many biological reactions.
Complete the table below by writing an appropriate term next to each description.
Description Term
The type of reaction that occurs when
water is added to break a bond in a
molecule.
The phosphate group of a
phospholipid that readily attracts
water molecules.
[Total 2 marks]
4. The enzyme DHPS is involved in the production of folic acid in bacteria.
• The substrate for DHPS is a molecule known as PABA.
• The enzyme DHPS is inhibited by the drug sulfonamide.
The figure below shows the structure of PABA and that of sulfonamide.
alevelbiology.co.uk
4
3.1 Biological Molecules
EXAM QUESTIONS BOOKLET
Use this booklet to revise for exams and improve exam
technique. Ensure you identify areas of strength and weakness
near exam time to make your revision effective, and use the
revision notes to fill in any gaps
alevelbiology.co.uk
1
,1. The figure below represents a water molecule.
Water molecules are polar. As a result, they attract each other.
Draw a second water molecule on the figure above.
Your drawing should show:
• The bond(s) between the two molecules
• The name of the bond
• The charges on each atom.
[Total 3 marks]
2. Ponds provide a very stable environment for aquatic organisms. Three properties of water that
contribute to this stability are as follows:
● The density of water decreases as the temperature falls below 4°C, so ice floats on the top of the
pond.
● It acts as a solvent for ions such as nitrates (NO3–).
● A large quantity of energy is required to raise the temperature of water by 1°C.
alevelbiology.co.uk
2
, Explain how these three properties help organisms survive in the pond.
In your answer you should make clear the links between the behaviour of the water molecules and
the survival of the organisms.
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.......................................................................................................................................................................
.......................................................................................................................................................................
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[Total 8 marks]
alevelbiology.co.uk
3
, 3. Water is important in many biological reactions.
Complete the table below by writing an appropriate term next to each description.
Description Term
The type of reaction that occurs when
water is added to break a bond in a
molecule.
The phosphate group of a
phospholipid that readily attracts
water molecules.
[Total 2 marks]
4. The enzyme DHPS is involved in the production of folic acid in bacteria.
• The substrate for DHPS is a molecule known as PABA.
• The enzyme DHPS is inhibited by the drug sulfonamide.
The figure below shows the structure of PABA and that of sulfonamide.
alevelbiology.co.uk
4
