Biological Importance of Water

Biological Importance of Water MDCAT MCQs with answers

19 past paper MCQs on Biological Importance of Water, from the Biological Molecules unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.Human bone cells contain what percentage of water? (MDCAT 2022)

  1. 20
  2. 40
  3. 85
  4. 90
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Correct answer: (a) 20

Bone is the driest tissue of the body, at about 20% water.

2.What is the percentage of water in bone cells? (MDCAT 2024)

  1. 70%
  2. 20%
  3. 98%
  4. 60%
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Correct answer: (b) 20%

Bone is the least watery of the tissues, with about a fifth of its weight as water.

3.Which property of water helps in moderating Earth's climate and maintaining stable temperature in aquatic environment? (UHS MDCAT 2025)

  1. Low viscosity
  2. High specific heat capacity
  3. High surface tension
  4. High polarity
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Correct answer: (b) High specific heat capacity

Water takes in a great deal of heat for a small rise in temperature, so it steadies the climate.

4.The high specific heat capacity of water is due to: (KMU MDCAT 2025)

  1. Ionic bonding
  2. Hydrogen bonding
  3. Covalent bonding
  4. Hydrophilic bonding
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Correct answer: (b) Hydrogen bonding

Much of the heat given to water goes into breaking hydrogen bonds rather than into motion.

5.Which properties of water enable it to circulate in living bodies and act as transport medium? (KMU MDCAT 2025)

  1. Ionization and low density
  2. Cohesion and ionization
  3. Ionization and adhesion
  4. Adhesion and cohesion
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Correct answer: (d) Adhesion and cohesion

Cohesion holds the column of water together and adhesion holds it to the walls of the vessel.

6.Water can circulate in living organisms due to: (SIBA MDCAT 2025)

  1. Surface tension and polarity
  2. Cohesion and adhesion .
  3. Solubility in cells
  4. Stable liquid range
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Correct answer: (b) Cohesion and adhesion .

Cohesion holds the water column together and adhesion holds it to the vessel wall.

7.Which property of water allows it to stick to polar surface like wood? (SIBA MDCAT 2025)

  1. Density
  2. Adhesion
  3. Cohesion
  4. Non-polar attraction
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Correct answer: (b) Adhesion

Adhesion is the attraction of water to a different polar surface.

8.The temperature of underground water remains constant due to: (SZABMU MDCAT 2025)

  1. Heat capacity
  2. Polarity of water
  3. Heat of vaporization
  4. Specific heat of vaporization
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Correct answer: (a) Heat capacity

Water takes in a great deal of heat for a small rise in temperature, so a body of it changes temperature slowly.

9.All of the following properties of water are associated with its capillary action. EXCEPT: (SZABMU MDCAT 2025)

  1. Adhesion
  2. Density
  3. Cohesion
  4. Surface tension
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Correct answer: (b) Density

Capillary rise depends on adhesion, cohesion and surface tension; the density only sets how high the column can be held.

10.Water commonly known as a universal solvent because: (SZABMU MDCAT 2025)

  1. It dissolves polar and ionic substances effectively
  2. It supports chemical reactions without reacting itself
  3. It has a high specific heat capacity
  4. It dissolves many substances due to its small molecule size
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Correct answer: (a) It dissolves polar and ionic substances effectively

Its molecules are polar, so they pull ions and polar molecules apart and surround them.

11.Which of the following structural change in water molecule leads to the low density of ice? (SZABMU MDCAT 2025)

  1. Formation of ionic bonds
  2. Expansion due to hydrogen bonding
  3. Increased kinetic energy
  4. Loss of polarity in molecules
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Correct answer: (b) Expansion due to hydrogen bonding

On freezing, the hydrogen bonds hold the molecules in an open lattice that takes up more room than the liquid.

12.Which property of water enables it to act as temperature stabilizer in living organisms? (SZABMU MDCAT 2023)

  1. High polarity
  2. Being non polar
  3. High specific heat capacity
  4. High heat of vaporization
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Correct answer: (c) High specific heat capacity

Water takes in a great deal of heat for a small rise in temperature, so it steadies the body.

13.Thermal stability of organisms in the environment is because of which characteristic of water? (NUMS MDCAT 2023)

  1. Solvent property
  2. Heat capacity
  3. Ionization
  4. Protection
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Correct answer: (b) Heat capacity

Water takes in a great deal of heat for a small rise in temperature, so it steadies the body.

14.Which type of bond must be broken for water to vaporize? (UHS MDCAT 2023)

  1. Nonpolar covalent bonds
  2. Polar covalent bonds
  3. Hydrogen bonds
  4. Covalent bonds
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Correct answer: (c) Hydrogen bonds

Vaporizing water means pulling its molecules apart, which breaks the hydrogen bonds between them.

15.___________ forms almost three-fourth of the body by weight (UHS MDCAT 2023)

  1. Water
  2. Protein
  3. Carbohydrates
  4. Lipids
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Correct answer: (a) Water

About three quarters of the mass of the body is water.

16.Due to its high heat of vaporization water plays important role in living organism as: (NUMS MDCAT 2022)

  1. Being an excellent solvent
  2. Cooling agent
  3. Membrane stabilizer
  4. Thermal shock resistor
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Correct answer: (b) Cooling agent

Evaporating a little sweat carries off a great deal of heat, which is how the body is cooled.

17.The attraction between water molecules and the cell wall of xylem is termed as: (PMC Practice 2021)

  1. Cohesion
  2. Tension
  3. Adhesion
  4. Imbibition
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Correct answer: (c) Adhesion

Water clinging to a different surface is adhesion; water clinging to itself is cohesion.

18.Water acts as a universal solvent because of: (PMC MDCAT 2020)

  1. Heat of vaporization
  2. Hydrogen bonding
  3. High polarity
  4. Cohesion and adhesion
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Correct answer: (c) High polarity

The water molecule is strongly polar, so it pulls ions apart and surrounds them.

19.If water has a high latent heat of vaporization, how could this property of water be helpful to plants and animals? (UHS MDCAT 2019)

  1. With the release of large amount of water, a small amount of heat loss can take place.
  2. With the release of small amount of water vapours, a great amount of heat loss can take place.
  3. It will keep their temperature very high.
  4. No cooling effect, with the release of even a large amount of water vapours.
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Correct answer: (b) With the release of small amount of water vapours, a great amount of heat loss can take place.

A little sweat carries off a great deal of heat, which is what makes evaporation such an efficient coolant.

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