Module 2: Biological Molecules - Water. Flashcards
What are 3 uses of Water?
It is used as a reactant in cells ( such as photosynthesis or hydrolysis)
Provides structural support in cells.
Keeps organisms cool to maintain an optimum body temperature.
What is a molecule of water?
A molecule of water is one atom of oxygen (O) joined to two atoms of hydrogen by shared electrons.
What does it mean by a Polar molecule?
A polar molecule is a molecule in which one end of the molecule is slightly positive, while the other end is slightly negative.
Describe the Polarity of Water.
The oxygen atoms in water are slightly negatively charged whereas the hydrogen atoms in water are slightly positively charge.
The polarity of water molecules means that a hydrogen atom on one water molecule is attracted to the oxygen atom on another water molecule. This is called Hydrogen Bonding.
What is Hydrogen Bonding?
It is when the slightly negatively charge oxygen atoms attract the slightly positively charge hydrogen atoms of other water molecules.
What are the 6 Properties of water.
High Specific Heat capacity.
High Latent heat of Vapourisation.
Good solvent.
Very Cohesive.
Metabolic Reactions.
Low Density when Solid.
Define High specific Heat Capacity.
It is the amount of heat 1kg of a substance must absorb or lose to change its temperature by 1 degree (C)
Explain why water has a High Specific Heat Capacity?
The hydrogen bonds between water molecules can absorb a lot of energy.
When water is heated, the heat energy goes towards weakening/breaking the hydrogen bonds rather than increasing the kinetic energy of water molecules.
Because of this, water acts as a buffer against rapid temperature changes. The temperature of water tends to not change rapidly
This allows water to act as a habitat for aquatic organisms. the temperature of water is likely to be more stable than it is on land.
Define High Latent heat of Vapourisation.
It is the amount of energy needed to change 1kg of a liquid substance to a gas.
Explain why water has a High Latent heat of Vapourisation.
It takes a lot of energy for hydrogen bonds to break between water molecules.
This allows organisms to cool themselves without losing a great amount of water.
I.e. = During sweating, heat energy is used to evaporate water from the surface of the skin and this transfer of heat energy allows the organisms to cool down.
Define solvent.
It is the substance that dissolves the solute to form a solution.
Why is water a good Solvent?
It is a good solvent because ions and polar molecules can easily dissolve in it.
Because water is a good solvent, it can be used to transport substances.
e.g. in the blood plasma.
What is Cohesion?
Cohesion is the attraction between molecules of the same type. (For example 2 water molecules)
Why is Water Cohesive?
Water molecules are very cohesive because they are polar.
Water molecules tend to stick together due to hydrogen bonds between them.
This helps water to flow, making it a great for transporting substances. Cohesion allows columns of water to travel in the xylem tubes.
It also causes surface tension where water meets air. Surface tension is useful as it allows the surface of water to act as a habitat.
This is why water forms water droplets rathe than being flattened out by gravity.
Why is water a good Metabolite?
Water is a reactant in many different reactions including hydrolysis and photosynthesis reactions.
Water is also produced in certain metabolic reactions, including condensation and aerobic respiration reactions.
