1.7 Water

Question 1

Explain how hydrogen bonds occur between water molecules

Answer 1

● Water is polar molecule
● Slightly negatively charged oxygen atoms attract slightly positively
charged hydrogen atoms of other water molecules

Question 2

Explain 5 properties of water that are important in biology

Answer 2

Metabolite:
Used in condensation / hydrolysis / photosynthesis / respiration

Solvent (can
dissolve solutes) :
1. Allows metabolic reactions to occur
2. Allows transport of substances eg. nitrates in xylem, urea in blood

(Relatively) high
specific heat
capacity :
● Buffers changes in temperature
● As can gain / lose a lot of heat / energy without changing temperature
1. Good habitat for aquatic organisms as temperature more stable than land
2. Helps organisms maintain a constant internal body temperature

(Relatively) large
latent heat of
vaporisation :
● Allows effective cooling via evaporation of a small volume (eg. sweat)
● So helps organisms maintain a constant internal body temperature

Strong cohesion
between water
molecules :
1. Supports columns of water in tube-like transport cells of plants
eg. transpiration stream through xylem in plants
2. Produces surface tension where water meets air, supporting small
organisms (to walk on water)