Water

Question 1

Water is a very important biological molecule.

Answer 1

60 - 70% of our bodies are water.

Question 2

What is the structure of water?

Answer 2

• has 1 oxygen atom and 2 hydrogen atoms
• is dipolar
• has an unevenly distributed charge

Question 3

What is meant by dipolar?

Answer 3

di meaning two and polar referring to charges

Question 4

How does water have an unevenly distributed charge?

Answer 4

The oxygen atom is slightly negative and the hydrogen atoms are slightly positive.

Question 5

What does δ+ and δ- mean?

Answer 5

δ+ means slightly positive and δ- means slightly negative.

Question 6

What bonds form between water molecules?

Answer 6

Hydrogen bonds

Question 7

The formation of hydrogen bonds between water molecules and the fact that water is dipolar result in 5 key properties of water:

Answer 7

• It is a metabolite
• An important solvent in reactions.
• Has a high specific heat capacity
• Has large latent heat of vaporisation
• Has strong cohesion between water molecules

Question 8

How is water a metabolite?

Answer 8

• involved in many reactions such as photosynthesis, hydrolysis and condensation
• it is essential that approximately 90% of the plasma in blood is water and the cytoplasm in cells is largely composed of water

Question 9

How is water being a good metabolite important?

Answer 9

Water is needed for metabolic reactions to occur

Question 10

What is meant by a good solvent?

Answer 10

• many substances dissolve in it
• polar or charged, molecules dissolve readily in water due to the fact water is dipolar
• slight positive charge on hydrogen atoms will attract any negative ions solutes
• slight negative charge on the oxygen atoms will attract any positive ions in solutes

Question 11

How is water being a good solvent important?

Answer 11

• many essential polar substances dissolve in water
• enables them to be transported easily around animals and plants
• either in blood or xylem to cells that are needed inside of the organism

Question 12

What is mean by high specific heat capacity?

Answer 12

• a lot of energy is required to raise the temperature of water
• due to some of the heat energy being used to break the hydrogen bonds
• useful to organisms as temperature of water remains relatively stable even if surrounding temperature fluctuates significantly

Question 13

How is water having a high specific heat capacity important?

Answer 13

• internal temperatures of plants and animals should remain relatively constant despite outside temperatures due to the fact a large proportion of the organism is water
• is important so that enzymes do not denature or reduce in activity with temperature fluctuations
• provides a stable environment in terms of temperature for aquatic organisms

Question 14

What is meant by large latent heat of vaporisation?

Answer 14

• a lot of energy is required to convert water in its liquid state to a gaseous state
• as energy is needed to break the H bonds between water molecules to turn it into a gas

Question 15

How is water having a large latent heat of vaporisation important?

Answer 15

• water provides a significant cooling effect.
• e.g when humans sweat they release water onto their skin
• large amounts of heat energy from the skin is transferred to the water to evaporate it
• removes a lot of heat and cools the organism

Question 16

What is meant by strong cohesion?

Answer 16

Cohesion is the term used to describe water molecules sticking together by hydrogen bonds.

Question 17

How is water having strong cohesion important?

Answer 17

• due to water molecules sticking together, when water moves up the xylem in plants it is a continuous column of water
• an advantage as it is easier to draw up a column rather than individual molecules
• also provides surface tension to water which enables small invertebrates to move and live on the surface, providing them a habitat away from predators within water