3.1.7 - Water

Question 1

Water is a major component of…

Answer 1

cells

Question 2

Explain how hydrogen bonds occur between water molecules

Answer 2

● Water is polar molecule
● Slightly negatively charged oxygen atoms attract slightly positively
charged hydrogen atoms of other water molecules
- Form a hydrogen bond between them

Question 3

Explain 5 properties of water that are important in biology

Answer 3

• Metabolite
  > Used in condensation / hydrolysis / photosynthesis / respiration
• Solvent (can
  dissolve solutes)
  1. Allows metabolic reactions to occur (faster in solution)
  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)