| The dipolar water molecule | - Has positive and negative poles
- So its dipolar |
| Water and hydrogen bonding | - Opposite charged molecules attract, hydrogen bonding
- Each bond is fairly weak
- Together they form important forces that cause cohesion |
| Specific heat capacity of water | - Takes lots of energy to separate molecules
- So the boiling point of water is higher than expected
- Water acts as a buffer against sudden temperature variations |
| Latent heat of vaporisation of water | - A lot of energy needed to evaporate 1 gram of water as molecules held together by hydrogen bonds |
| Cohesion and water | - Molecules sticking together
- Allows it to be pulled through tubes e.g xylem |
| Surface tension and water | - When water molecules meet air they tend to be pulled back into the body of water rather than escaping it
- Its strong enough to support small organisms |
| Water in metabolism | - Water used in hydrolysis + condensation reactions
- Needed in photosynthesis
- Chemical reactions take place in aqueous mediums |
| Water as a solvent | Dissolves:
- Gases such as O and CO2
- Ammonia and urea
- Inorganic ions and small hydrophilic molecules |
| Other important features of water | - Evaporation cools organisms, controls temperature
- Not easily compressed, provides support
- Transparent, aquatic plants can photosynthesise |
| Inorganic ions | - Found in cytoplasm and bodily fluids |
| Functions of inorganic ions | - Iron ions are found in haemoglobin, transport oxygen
- Phosphate ions have a structural role in DNA and ATP
- Hydrogen ions are important in determining pH
- Sodium ions in the co-transport of glucose and amino acids |
