Water

Biological molecules, Miss estruch

What is water in terms of polarity?

A dipolar molecule (two different charges)

Why does water have an unevenly distributed charge?

Because the oxygen atom is slightly negative whilst the hydrogen atoms are slightly positive

Name the 5 key properties of water

• Metabolite

• High latent heat of vaporisation

• High specific heat capacity

• Important solvent

• Has cohesion

Water is a metabolite. What does this mean?

It is involved in lots of chemical reactions such as hydrolysis

Which kinds of molecules are soluble in water and why?

Polar molecules because water is dipolar

What do the slight positive and negative charges on the hydrogens and oxygen in water attract in any solute?

• Slightly positive charge of hydrogen: negative ions in solute

• Slightly negative charge of oxygen: positive ions in solute

Water has a high specific heat capacity. What does this mean?

A lot of energy is required to raise the temperature of water

Why does water have a high SHC?

Because some of the heat energy is used to break the hydrogen bonds between water molecules

Why is the high SHC of water useful to plants and animas?

• Because the temperature of water remains stable, even if the temperature of the environment fluctuates significantly.

• The internal temperature of animals and plants remains stable b/c a large proportion of the organism is water

• This prevents enzymes from denaturing or reducing in activity

Why is the high SHC of water useful to aquatic organisms?

Because it provides a stable temperature environment for them

Water has high latent heat of vaporisation. What does this mean?

A lot of energy is required to convert liquid in its liquid state to a gaseous state.

Why does water have a high LH of vaporisation?

Because it requires lots of energy to break the hydrogen bonds between water molecules in order to turn it into a gas.

What is the advantage of water’s high LH to organisms?

• Provides a cooling effect

• For example- when we sweat, water molecules are released into our skin. Large amounts of heat energy from the skin is transferred to the water to evaporate it, removing heat and cooling off the body.

Water has strong cohesion. What does this mean?

Its molecules are powerfully attracted to each other, and can thus stick together, due to hydrogen bonds

What benefit does water’s strong cohesion give to plants?

• Water moves as a continuous column when moving up the xylem due to transpiration.

• This is more efficient than moving individual molecules

What benefit does water’s strong cohesion give to small invertebrates?

• It provides water’s surface tension

• This allows small invertebrates to move and live on the surface, providing them a habitat away from predators within water.