Biological Molecules - Water Flashcards
Describe the molecular structure of 1 molecule of water
*Water is made of one atom of oxygen and two atoms of hydrogen
*These are covalently bonded to each other
*This means the atoms share electrons
*This creates an uneven electron distribution across the molecule
*This produces different polarities across the water molecule which is called dipolar
*The oxygen becomes slightly negative
*The hydrogen becomes slightly positive
Why is water described as dipolar?
Water is described as dipolar due to the uneven distribution of electrons due to the covalent bond allowing the oxygen to be slightly negative and the hydrogen to be slightly positive,
Why is ice less dense than water?
*The hydrogen bonds fix the positions of the molecules slightly further apart than the average distance in a liquid state.
*Producing a giant rigid open structure (tetrahedral) that is less dense than liquid water.
Why does water being dipolar make it a good solvent?
- due to the uneven distribution of electrons within the molecule, with the oxygen atom having a slightly negative charge and the hydrogen atoms having a slightly positive charge, allowing it to easily dissolve.
Why is the property of water being less dense as a solid important?
*When temperatures drop below freezing the top layer of the aquatic habitat freezes
*As water is less dense as a solid it remains at the top and floats
*This produces an insulating layer for living in the aquatic life water below
What property of water allows it to act as a coolant?
*Water has a large latent heat of vaporization (a lot of energy is required to convert water from its liquid state to a gaseous state) due energy required to break the hydrogen bonds between water, making a cooling effect for plants/animals(transpiration/sweat).
What is cohesion?
*This is when water molecules bond to each other.
What is capillary action and why is it important?
Capillary action is important for moving water around.
What is adhesion?
*Water molecules bond to other substances. This causes capillary action.
What is a hydrogen bond?
A hydrogen bond is an attraction between two atoms that already participate in other chemical bonds. One of the atoms is hydrogen, while the other may be any electronegative atom, such as oxygen, chlorine, or fluorine. The partially positive hydrogens of one water molecule are electrically attracted to the partially negative oxygen atom of another water molecule. They are usually weak bonds but collectively provide strength.
What does specific heat capacity mean?
The specific heat capacity of a substance is the energy required to raise the temperature of the substance by 1 ∘ C
What are the molecular properties of water?
Its main roles include:
*Being a solvent
*Being a transport medium
*Being a coolant
*Being a habitat
What are the applications of cohesion and adhesion ?
This also enables surface tension where a body of water meets the air, these hydrogen bonds occur between the top layer of water molecules to create a sort of film on the body of water (this is what allows insects such as pond skaters to float)
Water is also able to hydrogen bond to other molecules, such as cellulose, which is known as adhesion
This also enables water to move up the xylem due to transpiration
How does cohesion lead to surface tension?
Surface tension is caused by water molecules being cohesive. At the surface, there are fewer water molecules to hydrogen bond which causes them to be more compact producing tension.
Explain five properties that make water important for organisms.
- Ice is less dense than water - this creates an insulating layer for animals underneath
- Cohesive - great attraction meaning it it a great transport medium - traveling through xylem in transpiration.
- High specific heat capacity - it buffers temp change
- Good solvent - it can transport ions in the body
- High latent heat vaporisation - needs a lot of energy to evaporate it is a coolant for mammals so it creates a cooling effect on the surface.
- Important metabolite - Hydrolysis / Photosynthesis
