3.1.7 Water

AQA A-level Biology 3.1.7 practice on Water, with free MCQs, clues and worked explanations drawn from the Biological molecules section of specification 7402.

Specification route
3.1.7
Question bank
22 questions
Course stage
AS / Year 12

Sample questions

QUESTION 1 · 3.1.7 · LEVEL 3

Which property of water makes it an important solvent in biological systems?

  • It is a polar molecule, allowing it to surround and dissolve other polar molecules and ions.
  • It has a relatively large latent heat of vaporisation.
  • It has strong cohesion between water molecules.
  • It has a high heat capacity to buffer changes in temperature.
Show clue

Solvents need to interact electrically with solutes to pull them apart.

Show answer and explanation

Answer: It is a polar molecule, allowing it to surround and dissolve other polar molecules and ions.

Water is an important solvent in which metabolic reactions occur. Its polarity allows it to form hydration shells around ions and polar molecules, effectively dissolving them.

QUESTION 2 · 3.1.7 · LEVEL 2

How does water's relatively high heat capacity benefit living organisms?

  • It buffers changes in temperature, providing a stable internal environment.
  • It allows water to evaporate easily, providing a rapid cooling effect.
  • It enables water columns to be pulled up the xylem without breaking.
  • It allows metabolic reactions to occur rapidly at low temperatures.
Show clue

Think about habitats like lakes and the temperature of warm-blooded animals.

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Answer: It buffers changes in temperature, providing a stable internal environment.

Water has a relatively high heat capacity, buffering changes in temperature. This means a lot of energy is required to raise the temperature of water, ensuring stable aquatic habitats and internal cellular temperatures.

QUESTION 3 · 3.1.7 · LEVEL 2

What physical phenomenon is a direct result of strong cohesion between water molecules at the interface between water and air?

  • Surface tension
  • High specific heat capacity
  • Latent heat of vaporisation
  • Hydrolysis
Show clue

This property allows insects like pond skaters to walk on water.

Show answer and explanation

Answer: Surface tension

Water has strong cohesion between water molecules; this produces surface tension where water meets air, acting like a 'skin'.

QUESTION 4 · 3.1.7 · LEVEL 2

Which property of water provides a cooling effect with little loss of water through evaporation?

  • A relatively large latent heat of vaporisation
  • A relatively high heat capacity
  • Strong cohesion between water molecules
  • Its role as an important solvent
Show clue

This property relates to the energy required to turn liquid water into a gas.

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Answer: A relatively large latent heat of vaporisation

Water has a relatively large latent heat of vaporisation, providing a cooling effect with little loss of water through evaporation.

QUESTION 5 · 3.1.7 · LEVEL 3

Why is the strong cohesion between water molecules biologically important in plants?

  • It supports columns of water in the tube-like transport cells of plants
  • It buffers changes in plant body temperature
  • It provides a cooling effect through transpiration
  • It directly fuels the condensation reactions in photosynthesis
Show clue

Cohesion allows water to be pulled up through the xylem.

Show answer and explanation

Answer: It supports columns of water in the tube-like transport cells of plants

Water has strong cohesion between water molecules; this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air.

QUESTION 6 · 3.1.7 · LEVEL 2

Which of the following processes requires water as a metabolite?

  • Hydrolysis reactions
  • Condensation reactions
  • DNA helicase activity
  • Semi-conservative replication
Show clue

This reaction uses a water molecule to break chemical bonds.

Show answer and explanation

Answer: Hydrolysis reactions

Water is a metabolite in many metabolic reactions, including condensation and hydrolysis reactions. (Note: Condensation produces water, but hydrolysis specifically requires it as an active reactant).

QUESTION 7 · 3.1.7 · LEVEL 2

Which of the following describes water's role as a metabolite?

  • It is used to break chemical bonds in hydrolysis reactions.
  • It buffers changes in temperature.
  • It provides a cooling effect with little loss of water.
  • It provides strong cohesion between molecules.
Show clue

A metabolite is a substance involved directly in a metabolic reaction.

Show answer and explanation

Answer: It is used to break chemical bonds in hydrolysis reactions.

Water is a metabolite in many metabolic reactions, including condensation and hydrolysis reactions.

QUESTION 8 · 3.1.7 · LEVEL 1

Where water meets air, strong cohesion between water molecules results in which phenomenon?

  • Surface tension
  • Latent heat of vaporisation
  • A high heat capacity
  • The formation of ice
Show clue

This allows some small insects to walk on the surface of ponds.

Show answer and explanation

Answer: Surface tension

Water has strong cohesion between water molecules; this... produces surface tension where water meets air.

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