3.1.7 Water Flashcards
Name a function of water in reactions?
A metabolite in many metabolic reactions
Give 2 examples of reactions where water acts as a metabolite?
Condensation
Hydrolysis
What is the main cause of waters unusual properties?
It’s dipolar nature and the hydrogen bonding this allows
What makes a water molecule dipolar?
It is made up of two atoms of hydrogen and one of oxygen
The oxygen has a slight negative charge
The hydrogen has a slight positive charge
So the water molecule has both positive and negative poles
Why do water molecules stick together?
The positive pole of one water molecule is attracted to the negative pole of another water molecule
The attractive forces form a hydrogen bond
Hydrogen bonds in high quantities are strong
How do water’s properties act as a buffer against sudden temperature change?
The hydrogen bonding takes more energy to separate the water molecules
Taking more energy to heat a given mass of water means it has high specific heat capacity
Therefore it would take a lot of energy to change temperature in aquatic conditions
This is good for aquatic animals because they expend less energy on temperature control
Describe the latent heat of vaporisation of water.
Hydrogen bonding means it takes a lot of energy to evaporate 1 gram of water
Evaporation of water such as sweat is an effective way of cooling as heat is used to evaporate the water
How does waters cohesive properties aid plants?
Strong hydrogen bonding
Large cohesive forces
Allows it to be pulled up a tube
Eg xylem vessel in plants
How does surface tension in water aid organisms?
Where water molecules meet air they are pulled back into the body of water
This is surface tension
This acts like a skin strong enough to support organisms like pond skaters
Why is water important?
It makes up 65% of most mammals
Where life on earth arose
Is the habitat for many species
In what ways is water important in metabolism?
Hydrolysis breaks down complex molecules and condensation reactions produce water
Chemical reactions take place in an aqueous medium
Water is a major raw material in photosynthesis
Water is a solvent. What can it readily dissolve?
Gases- O2, CO2, etc
Wastes- ammonia, urea, etc
Inorganic ions and small hydrophilic molecules- amino acids, monosaccharides and ATP
Enzymes- whose reactions take place in a solution
Give three useful features of water.
Evaporation- cools down organisms
Not easily compressed- provides support (eg the hydrostatic skeleton of animals like the earthworm)
Transparent- aquatic plants can photosynthesise and light rays can reach the retina past the eyes fluid
How are inorganic ions useful in organisms?
Iron ions- in haemoglobin to aid oxygen transport
Phosphate ions- structural role in DNA molecules/ a role in storing energy in ATP molecules
Hydrogen ions- determining pH of solutions for enzyme function
Sodium ions- transport of glucose and amino acids across plasma membranes
