Water

• Water is one of the most useful molecules in life, with its uses including being a reactant, providing structural support in cells and keeping organisms cool to maintain an optimum body temperature.
• Water is a polar molecule, as the oxygen atoms have a slight negative charge and the hydrogen atoms have a slight positive charge
• What atom in water has a slight negative charge?

  Oxygen
• What atom in water has a slight positive charge?

  Hydrogen
• The polarity of water molecules means that a hydrogen atom on one water molecule is attracted to the oxygen atom on an adjacent water molecule, this attraction is called hydrogen bonding.
• What is hydrogen bonding?

  Attraction between a hydrogen atom and an electronegative atom (oxygen in water).
• Hydrogen bonding is weak when there are few of them, so they are constantly breaking and reforming, however, when there is a large number of them, they form a strong structure.
• What type of force are hydrogen bonds?

  Intermolecular
• What is the main type of bonding in water molecules?

  Hydrogen bonding
• Water is a good metabolite
• Water is used or formed in many metabolic reactions, such as condensation and hydrolysis reactions, for example the hydrolysis of ATP, in which a bond is broken and a molecule of water is used up, making this a hydrolysis reaction.
• What is an example of water being used in a reaction?

  Hydrolysis reactions, such as the hydrolysis of ATP
• What is an example of water being formed in a reaction?

  Condensation reactions, such as ATP synthesis
• The regeneration of ATP involves water, as a new bond is formed and a water molecule is released, making this a condensation reaction.
• In hydrolysis reactions, one molecule of water is used.
• In condensation reactions, one molecule of water is released
• Specific heat capacity is the amount of thermal energy required to raise the temperature of 1kg of a substance by 1 degree
• Water has a high specific heat capacity
• Water has a high specific heat capacity, meaning that a relatively large amount of energy is required to raise its temperature, this is due to the many hydrogen bonds present in water.
• Why does water have a high specific heat capacity?

  Many hydrogen bonds are present, and it takes a large amount of thermal energy to break and build them, therefore, the temperature of water does not fluctuate greatly.
• What is an advantage of water having a high specific heat capacity?

  Provides suitable habitats for sea life
• What is an advantage of water having a high specific heat capacity?

  Its able to maintain a constant temperature as water is able to absorb a lot of heat without big temperature changes, this is vital in maintaining temperatures that are optimal for enzyme activity.
• What is an advantage of water having a high specific heat capacity?

  As blood plasma passes through the more active and warmer regions of the body, heat energy is absorbed but the temperature remains fairly constant. Water in tissue fluid also plays an important regulatory role in maintaining a constant body temperature.
• Water in blood plasma is also vital in transferring heat around the body, helping to maintain a fairly constant temperature, for example, as blood passes through the more active, warmer regions of the body, heat energy is absorbed but the temperature remains fairly constant.
• Water has a high specific latent heat of vaporisation
• The specific latent heat of vaporisation is the amount of energy needed to change the state of 1kg of a substance from a liquid to a gas
• As liquid water heats up, hydrogen bonding makes it difficult to separate the water molecules from each other, this means that a lot of thermal energy is required to break the hydrogen bonds for water to evaporate.
• Why does water have a high latent heat of vaporisation?

  Hydrogen bonding makes it difficult to separate the water molecules from each other, this means that a lot of thermal energy is required to break the hydrogen for water to evaporate.
• How is having a high latent heat an advantage?

  Only little amounts of water are required to evaporate for the organism to lose a great amount of heat, providing a cooling effect for living organisms
• An example of high latent heat of water is transpiration from leaves or evaporation of water in sweat on skin
• Water is cohesive and adhesive, meaning it can stick to itself and other substances
• The strong intermolecular forces (hydrogen bonding) between water molecules allows for strong cohesion between water molecules.
• Why does water have strong cohesion?

  The strong hydrogen bonding between water molecules
• The strong cohesion between water molecules allows columns of water to move through the xylem of plants and through blood vessels in animals.
• What is water cohesion?

  Water sticking to itself
• The strong cohesion between water molecules enables surface tension where a body of water meets air, these hydrogen bonds occur between the top layer of water molecules to create a kind of film on the body of water.
• Plants use surface tension to help transport water from their roots to their leaves.
• Water is able to hydrogen bond to other molecules, such as cellulose, which is known as adhesion.
• Adhesion helps plant cells stick together by forming hydrogen bonds with the cell walls made up of cellulose.
• What is water adhesion?

  When water forms hydrogen bonds to other substances