lOMoARcPSD|15424936
Biological Molecules and Metabolic Pathway
BTEC UNIT 10
BIOLOGICAL NOLECULES
AND METABOLICAL
PATHWAY STUDY GUIDE
2023 COMPLETE
, lOMoARcPSD|15424936
Biological Molecules and Metabolic Pathways
Biological molecules and biochemical processes
Water molecules
Structure:
❖ Water is made up of two hydrogen atoms covalently bonded to one oxygen
atom
❖ Each of the hydrogen atoms shares a pair of electrons with oxygen to form a
covalent bond.
❖ The oxygen has a greater affinity for electrons than the hydrogens, therefore it
pulls the electrons closer.
❖ This makes the oxygen slightly negative and the hydrogen slightly positive.
Importance of water:
Water is an universal solvent and has many different functions including:
❏ It acts as a transport for molecules
❏ It acts as a medium for chemical reactions
❏ It regulates the pH level
❏ It a temperature regulator for our body
❏ It also balances electrolyte.
Water is a good solvent for chemical reactions because any molecules that are polar will dissolve in water.
This happens because the solute also has an uneven charge distribution across the molecules. Water also
has the ability to resist temperature changes as it takes a high level of energy to change the temperature due
to the strong hydrogen bonding. To break the hydrogen bonds, the temperature has to rise and the water
molecules then gain more kinetic energy and vibrate more. It’s only at pH 7 that the water has equal
concentration of H and OH ions.
Water molecules are polar, so they form many hydrogen bonds which give water unique properties like its high
boiling points, high specific heat capacity, adhesion and density.
Carbohydrates
Carbohydrates are compounds that contain carbon, hydrogen and oxygen and the general formula is
Cх(HշO )y.
There are mainly three groups of carbohydrates:
1. Monosaccharides which are simples sugars or one sugar molecules.
2. Disaccharides which are two sugar molecules.
3. Polysaccharides which are many sugars.
Monosaccharides
These are soluble in water, they are sweet in taste and they form
crystals. And the 3 examples are:
① Glucose is the energy source in cells and the main respiratory
nutrient.
② Fructose is the main sugar found in fruits.
③ Galactose is used for making glycolipids and glycoprotein.
These are all called hexose sugars because they contain 6 carbon
atoms.
Ring forms of hexose sugars:
Glucose (6 carbon atoms)
The only difference between them is
the position of the hydrogen and
hydroxyl groups on carbon 1. In α-
glucose the OH group on carbon 1
is below the ring and in β-glucose
the OH group on carbon 1 is above
Pentosethe
sugars
ring. (5 carbon atoms)
Biological Molecules and Metabolic Pathway
BTEC UNIT 10
BIOLOGICAL NOLECULES
AND METABOLICAL
PATHWAY STUDY GUIDE
2023 COMPLETE
, lOMoARcPSD|15424936
Biological Molecules and Metabolic Pathways
Biological molecules and biochemical processes
Water molecules
Structure:
❖ Water is made up of two hydrogen atoms covalently bonded to one oxygen
atom
❖ Each of the hydrogen atoms shares a pair of electrons with oxygen to form a
covalent bond.
❖ The oxygen has a greater affinity for electrons than the hydrogens, therefore it
pulls the electrons closer.
❖ This makes the oxygen slightly negative and the hydrogen slightly positive.
Importance of water:
Water is an universal solvent and has many different functions including:
❏ It acts as a transport for molecules
❏ It acts as a medium for chemical reactions
❏ It regulates the pH level
❏ It a temperature regulator for our body
❏ It also balances electrolyte.
Water is a good solvent for chemical reactions because any molecules that are polar will dissolve in water.
This happens because the solute also has an uneven charge distribution across the molecules. Water also
has the ability to resist temperature changes as it takes a high level of energy to change the temperature due
to the strong hydrogen bonding. To break the hydrogen bonds, the temperature has to rise and the water
molecules then gain more kinetic energy and vibrate more. It’s only at pH 7 that the water has equal
concentration of H and OH ions.
Water molecules are polar, so they form many hydrogen bonds which give water unique properties like its high
boiling points, high specific heat capacity, adhesion and density.
Carbohydrates
Carbohydrates are compounds that contain carbon, hydrogen and oxygen and the general formula is
Cх(HշO )y.
There are mainly three groups of carbohydrates:
1. Monosaccharides which are simples sugars or one sugar molecules.
2. Disaccharides which are two sugar molecules.
3. Polysaccharides which are many sugars.
Monosaccharides
These are soluble in water, they are sweet in taste and they form
crystals. And the 3 examples are:
① Glucose is the energy source in cells and the main respiratory
nutrient.
② Fructose is the main sugar found in fruits.
③ Galactose is used for making glycolipids and glycoprotein.
These are all called hexose sugars because they contain 6 carbon
atoms.
Ring forms of hexose sugars:
Glucose (6 carbon atoms)
The only difference between them is
the position of the hydrogen and
hydroxyl groups on carbon 1. In α-
glucose the OH group on carbon 1
is below the ring and in β-glucose
the OH group on carbon 1 is above
Pentosethe
sugars
ring. (5 carbon atoms)
