2.1.2 - Biological Molecules Flashcards
What kind of molecule is water?
Water is polar covalently bonded within molecule.
What does water being polar mean?
The unequal sharing of the electrons results in a slightly positively and slightly negative side of the molecule.
What are water molecules held together by?
Why?
Hydrogen bonds
Because of the attraction between the + and - poles.
What is cohesion?
The tendency of water molecules to stick together.
(3) What are the consequences of cohesion?
- High melting and boiling point.
- High specific heat capacity.
- High latent heat of vaporisation.
What is the significance of a high boiling point?
It means water is a liquid at Earth surface temperatures.
(2) What is the significance of a high specific heat capacity?
- Aquatic habitats remain at fairly stable temperatures, cooling/warming slowly.
- Bodies of living organisms are also temperature stable and they have to lose/absorb a lot of energy to become cooler/warmer.
What is the significance of a high latent heat of vaporisation?
Evaporation of water can be harnessed as a very effective cooling system.
What is dissolution?
When water molecules can easily move between ions or other polar molecules and separate them.
What is dissolution?
When water molecules can easily move between ions or other polar molecules and separate them.
What does hydrophilic mean?
Substances that are polar and often water-soluble.
What does hydrophobic mean?
Substances that repel water, causing droplets to form. They are often non-polar.
What is an example of a hydrophobic substance?
Lipids lack polar bonds. Polar covalently bonded water molecules act to exclude non-polar molecules which cause the fats to clump together.
(3) Why is the hydrophobic nature of fats advantageous?
It makes fats useful storage units as:
* They stay together in one compact unit.
* Can’t react.
* Have no osmotic effect on the cell.
At what temperature does water reach its maximum density?
4°C
What does this mean?
When ponds and lakes cool they first freeze at the top meaning aquatic organisms can stay alive beneath the ice as it provides an insulating layer, reducing further cooling.
