StemUp: AQA A level Biology 3.1.7 Water

How do the properties of water relate to its function in metabolic reactions? (4)

- Acts as a metabolite in many reactions

- Including condensation and hydrolysis reactions

- It is required for photosynthesis

- It is a metabolic product of respiration, which is important for organisms living in dry habitats

How do the properties of water relate to its function as a solvent? (3)

- Transports nutrients e.g. glucose in blood and sucrose in phloem of plants

- Removes excretory products e.g. urea and ammonia

- Acts as a medium in which metabolic reactions can occur

Why is water sometimes referred to as a buffer? (1)

It can resist changes in temperature via its properties

What properties of water relate to its function in regulating temperature in animals and plants? (2)

- High heat capacity

- Large latent heat of vaporisation

What does water's high heat capacity mean? (1)

Water will absorb a large amount of heat energy before rising‎ ‎‎in temperature

How does water's high heat capacity relate to its function in temperature regulation? (2)

- Minimises increases in temperature within cells as a result of biochemical reactions e.g. respiration

- Helps to prevent dangerous fluctuations in temperature in aquatic habitats

What does water's large latent heat of vaporisation mean? (1)

The amount of energy required to break the hydrogen bonds between water molecules

How does water's large latent heat of vaporisation relate to its function in temperature regulation? (3)

- Provides a cooling effect in both animals and plants

- Which helps some animals maintain a constant body temperature as a high amount of heat energy is removed from the body to evaporate sweat

- Cooling effect in plants via transpiration

Briefly describe the polarity of water (3)

- Oxygen atoms have a delta negative charge

- Hydrogen atoms have a delta positive charge

- These slight charges can lead to attraction, called hydrogen bonding

NOTE: This isn't specifically on the specification however, it is key to understanding the 'supporting' properties of water

How does the strong cohesive forces in water arise from? (2)

- Due to hydrogen bonding between water molecules

- Which is caused by the polarity of water that causes molecules to stick together

How does water's strong cohesive forces relate to its function as a supporting molecule? (3)

- Supports water columns in tube-like transport cells e.g. xylem of plants, allowing transport from roots to leaves

- Produces surface tension where water meets air

- Which enables insects to walk on the surface of water (e.g. pond skaters) or be suspended at surface (e.g. mosquito larvae)

What are some other properties of water that allow it to act as a supporting molecule?

- Provides turgor pressure for support in non-woody plants

- Provides buoyancy for aquatic organisms e.g. whales