Iesa Majeed
Biological Molecules and Biochemical Processes
Water structure, bonding and importance
Water is a small molecule with the formula H2O, it consists of two hydrogen atoms and one
oxygen atom. They are in a 2:1 ratio. These atoms are covalently bonded together. This
means they share electrons to create a strong electrostatic attraction.
These electrons are not shared evenly and as shown in the diagram, the oxygen atom pulls
the negatively charged electrons towards it away from the hydrogen atoms. This is because
oxygen is more electronegative than hydrogen thus creating uneven distribution across the
molecule.
Water is therefore described as a polar molecule due to there being more negative charge
at the oxygen atom and positive charge at the hydrogen atoms. The structure of the water
molecule is a result of the charges of the hydrogen atoms, where there is a delta + bond to
the delta – bonds on the oxygen atom.
These Hydrogen bonds are essential for some of the unique properties of water, such as the
high heat of vaporisation of water. The bonds between the atoms are extraordinarily strong
and requires substantial amounts of energy to cause water to become vapour. These strong
bonds allow water to remain liquid in a wide range of temperatures.
1
,Iesa Majeed
The importance of water
Water is particularly important and has many functions. These include:
As a transport of molecules
Water is a good transporter medium in living organism as it stays as a liquid over a wide
temperature range.
Acts as a medium for chemical reactions
All metabolic processes in organisms rely on chemical being able to interact together in a
solution. Water is a good solvent for chemical reactions because the polar molecules can
dissolve in the negatively charged polar water molecules due to waters’ uneven charge
distribution across itself.
2
, Iesa Majeed
Regulating pH
Since water has an equal distribution of positively charge hydrogen and negatively charged
oxygen, its pH is at level 7. Living organism are overly sensitive to pH levels and function
best when at its internal condition and closest to its ideal pH. Therefore, water plays a key
role in regulating the pH in living organisms. Water can accept and donate H+ where needed
and plays a significant role in keeping pH steady. It can also function as a buffering solution
where water can resist changes in pH due to its ability to donate ions, thus without water
solutions it would not be able to keep the required pH.
Temperature regulator
As water requires a large amount of energy to change its temperature, this gives it the
ability to withstand large temperature changes. The hydrogen bonds between water
molecules gain more kinetic energy as the temperature rises. This takes a lot of energy to
cause the moles of water to gain enough energy to vibrate and break the hydrogen bonds,
as many organisms are composed of water, which means that they can regulate their
internal temperature. Organisms need a steady temperature, as the chemical and enzyme
processes work within a narrow temperature band.
Electrolyte balance
Water plays a vital role in electrolyte imbalance. When extracellular concentration rises,
water can diffuse out of the cell via osmosis into the extra cellular base to lower and
equalise the electrolyte levels.
Carbohydrates
Carbohydrate (also called saccharides) are molecular compounds which are an essential part
of a living organism’s diet. Carbohydrates supply the energy organisms need to fuel the
cellular reactions and structural support required inside living cells. They are also referred to
as hydrated carbons.
Cells attach carbohydrate molecules to proteins and lipids. They change the structure to
enhance their functionality.
3
Biological Molecules and Biochemical Processes
Water structure, bonding and importance
Water is a small molecule with the formula H2O, it consists of two hydrogen atoms and one
oxygen atom. They are in a 2:1 ratio. These atoms are covalently bonded together. This
means they share electrons to create a strong electrostatic attraction.
These electrons are not shared evenly and as shown in the diagram, the oxygen atom pulls
the negatively charged electrons towards it away from the hydrogen atoms. This is because
oxygen is more electronegative than hydrogen thus creating uneven distribution across the
molecule.
Water is therefore described as a polar molecule due to there being more negative charge
at the oxygen atom and positive charge at the hydrogen atoms. The structure of the water
molecule is a result of the charges of the hydrogen atoms, where there is a delta + bond to
the delta – bonds on the oxygen atom.
These Hydrogen bonds are essential for some of the unique properties of water, such as the
high heat of vaporisation of water. The bonds between the atoms are extraordinarily strong
and requires substantial amounts of energy to cause water to become vapour. These strong
bonds allow water to remain liquid in a wide range of temperatures.
1
,Iesa Majeed
The importance of water
Water is particularly important and has many functions. These include:
As a transport of molecules
Water is a good transporter medium in living organism as it stays as a liquid over a wide
temperature range.
Acts as a medium for chemical reactions
All metabolic processes in organisms rely on chemical being able to interact together in a
solution. Water is a good solvent for chemical reactions because the polar molecules can
dissolve in the negatively charged polar water molecules due to waters’ uneven charge
distribution across itself.
2
, Iesa Majeed
Regulating pH
Since water has an equal distribution of positively charge hydrogen and negatively charged
oxygen, its pH is at level 7. Living organism are overly sensitive to pH levels and function
best when at its internal condition and closest to its ideal pH. Therefore, water plays a key
role in regulating the pH in living organisms. Water can accept and donate H+ where needed
and plays a significant role in keeping pH steady. It can also function as a buffering solution
where water can resist changes in pH due to its ability to donate ions, thus without water
solutions it would not be able to keep the required pH.
Temperature regulator
As water requires a large amount of energy to change its temperature, this gives it the
ability to withstand large temperature changes. The hydrogen bonds between water
molecules gain more kinetic energy as the temperature rises. This takes a lot of energy to
cause the moles of water to gain enough energy to vibrate and break the hydrogen bonds,
as many organisms are composed of water, which means that they can regulate their
internal temperature. Organisms need a steady temperature, as the chemical and enzyme
processes work within a narrow temperature band.
Electrolyte balance
Water plays a vital role in electrolyte imbalance. When extracellular concentration rises,
water can diffuse out of the cell via osmosis into the extra cellular base to lower and
equalise the electrolyte levels.
Carbohydrates
Carbohydrate (also called saccharides) are molecular compounds which are an essential part
of a living organism’s diet. Carbohydrates supply the energy organisms need to fuel the
cellular reactions and structural support required inside living cells. They are also referred to
as hydrated carbons.
Cells attach carbohydrate molecules to proteins and lipids. They change the structure to
enhance their functionality.
3
