Water And Its Functions Flashcards
Why does water have a dipole?
The oxygen carries a small negative charge
The hydrogen carries a small positive charge
Why do hydrophilic substances dissolve in water?
They readily form hydrogen bonds with water molecules.
What role does water play in metabolic reactions?
Water is a metabolite in many metabolic reactions, including hydrolysis and condensation reactions.
What are non-polar molecules in relation to water?
Non-polar molecules are hydrophobic and do not dissolve in water.
What does it mean for a substance to be hydrophobic?
Hydrophobic substances are insoluble in water.
Solutes (which dissolve in water) are said to be…
Hydrophilic because they readily dissolve in water
What bond forms between the O and H in water
Hydrogen bonds
What is high specific heat capacity?
It requires a lot of energy to raise the temperature of water because molecules stick together due to hydrogen bonding.
Why is the boiling point of water higher than expected?
The boiling point of water is higher than expected due to hydrogen bonding; without it, water would be a gas at room temperature.
Why is high specific heat capacity useful?
It creates a stable environment to live in.
Importance of high specific heat capacity in water
-maintains relatively constant temperature
-organisms living in aquatic environments don’t experience large fluctuations of temp
Why does water have a high latent heat of evaporisation
Takes a lot of energy to change it from a liquid to a gas
High latent heat of evaporisation importance in water
-good coolant( when we sweat the water uses heat energy from our body to evaporate therefore cooling us down
What is useful about water have cohesion
Cohesion allows a column of water to be pulled up through xylem vessels in plants from the roots to the top
What is useful about water have surface tension
The hydrogen bonds between neighbouring water molecules cause a ‘film’ to develop at the surface which can support small organisms such as pond skaters
Why is water important in metabolic reactions?
-water is used in the break down of complex molecules (eg polysaccharides and monosaccharides) by hydrolysis and is produced in condensation reactions
-metabolic reactions take place in an aqueous medium
-water is used in photosynthesis and is released in respiration
Why is water used as a solvent?
-More substances will dissolve in water than any other liquid
-non polar molecules such as lipids will NOT dissolve
Ions attract water molecules…
…then the water molecule ‘encases’ them
What is the importance of water being a solvent
-blood plasma mostly consists of water and transports dissolved substances such as glucose
-the cytoplasm in cells contain high percentage of water many chemical reactions take place here
-plants transport solution in the xylem and phloem
Describe the structure and bonding of water
Water molecules form a lattice held by hydrogen bonds. This means that the water molecules are closest at 4 degrees c and this is when water is most dense
Importance
Maximum density at 4 degrees c provides up thrust to support aquatic organisms eg whales
The importance of ice
-Ice floats on the surface of water which insulates large bodies of water from further heat loss and the bottom of the body of water remains as a liquid allowing life to continue
The importance of water being transparent
-light can penetrate so plants can photosynthesise
-light rays can pass through the jelly like vitreous humour fluid in the eye and reach the retina
Importance of water not being easily compressed
-provides support and maintains shape and structure of some organisms
-the hydrostatic skeleton in the earthworm
-turgor pressure in plants
Why is water a liquid at normal temperatures and pressures? And what is its biological significance?
Hydrogen bonds form between water molecules keep the molecules close enough together so that is a liquid
Water can be used as a medium for mass transport. Small molecules and ions can move by diffusion
Why does water have a high specific heat capacity (the amount of energy required to raise the temperature of 1kg by 1•C)
When water is heated a large amount of energy is required to break the hydrogen bonds and raise the temperature of the water. Hydrogen bonds also release heat when they form. This means that the temperature of the water remains relatively constant and any temperature fluctuations are slow.
What is the biological significance of having high specific heat capacity
Acts as a thermal buffer. Easier for organisms that are comprised of 70-90% water to maintain a stable body temperature. The temperature of oceans/lakes changes slowing providing a stable habitat for aquatic organisms
Why does water have high latent heat of vaporisation
To make a water molecule evaporate and become water about the hydrogen bonds between each molecule must be broken by the increased kinetic energy that each water molecule has
What is the biological significance of water having high latent heat of evaporation
When a small volume of water evaporates from the surface of an organism it requires a large amount of heat taken form the organism cooling it down (sweating)
Why is ice less dense than water
In I’ve, water molecules form a lattice held together by hydrogen bonds. This means that the water molecules are closest at 4•C and this is when water is most dense
What is the biological significance of ice being less dense that water
When water freezes the ice formed is less dense and floats on the surface which insulates large bodies of water form further heat loss and the bottom of the body of water remains a liquid allowing life to continue
Why is water a good solvent
As a dipole the molecules of water are able to coat the surfaces of small polar molecules and then dissolve. Hyde dipole nature also causes some compounds to separate in solution
What is the biological significance of water being a solvent
Important for the transport sector f substances and metabolic reactions like condensation and hydrolysis
Why why does water have high cohesion but low viscosity
The small particle size means that water has a low viscosity (flows easily) As each water molecule is joined together with the meals by hydrogen bonds there is a high cohesion between water molecules
What is the biological significance of water having high cohesion but low viscosity
High cohesion means water forms a continuous column and can flow through tubes with a narrow lumen (hole) e.g capillaries and xylem vessels.High cohesion also creates surface tension that can support small organisms
