Biological molecules
Monomers are small molecules that can be joined together by covalent bonds
in a condensation reaction to make polymers. Polymers can be broken down
into monomers with a hydrolysis reaction.
Polymer – large molecule made up of repeating smaller molecules called
monomers.
Condensation- chemical process where two molecules combine by the
elimination of water.
Hydrolysis reaction- the breaking down of a large molecule into smaller ones
by the addition of water molecules.
Polymerisation- the process by which polymers form.
Each condensation of two monomers eliminates one molecule of water.
Amino acid +amino acid= dipeptide + water
Glycerol + 3 fatty acids = triglyceride + water
Carbohydrates
Carbohydrates are molecules which consist only of carbon, hydrogen and
oxygen and they are long chains of sugar units called saccharides. A single
monomer is called a monosaccharide with a pair of monomers being called a
disaccharide. Combining many monosaccharides results in the formation of a
polysaccharide. These are all joined together with a glycosidic bond formed in
a condensation reaction.
Carbon containing molecules are called organic molecules.
Monosaccharides
Glucose is a monosaccharide containing six carbon atoms in each molecule and
is the main substrate for respiration and it’s the main way carbohydrates are
transported around the body of animals. It has two isomers – alpha and beta
glucose.
Common monosaccharides include glucose, galactose
and fructose. These are typically sweet tasting, soluble
substances which have the general formula (CH2O)n where n can any number
from three to seven.
, Disaccharides:
Two monosaccharides can join together in a condensation reaction to form a
disaccharide. In this process a molecule of water is produced. The diagram
below shows the formation of a 1-4 glycosidic bond between two alpha
glucose molecules in order to form a molecule of maltose. In maltose, sucrose
and galactose the bond is always alpha 1-4 glycosidic bond.
Glucose + glucose = maltose
Glucose + fructose = sucrose
Glucose + galactose = lactose
Polysaccharides
Polysaccharides are formed from many glucose units joined together and
include:
- Glycogen and starch which are both formed by the condensation of
alpha glucose.
- Cellulose formed by the condensation of beta glucose.
Glycogen is the main energy storage molecule in animals and is formed from
many molecules of alpha glucose joined together by 1, 4 and 1, 6 glycosidic
bonds. It has a large number of branches meaning that energy can be released
quickly as enzymes can act simultaneously on these branches which is good for
animals with a high metabolic and respiratory rate as it can readily be broken
down into glucose and used in respiration. Moreover, it is a relatively large but
compact molecule, thus maximising the amount of energy it can store in a
small space. Finally being insoluble means it will not affect the water potential
of cells so doesn’t tend to draw water into the cell and cannot diffuse out of
cells. It is stored as small granules in the muscles and the liver
Monomers are small molecules that can be joined together by covalent bonds
in a condensation reaction to make polymers. Polymers can be broken down
into monomers with a hydrolysis reaction.
Polymer – large molecule made up of repeating smaller molecules called
monomers.
Condensation- chemical process where two molecules combine by the
elimination of water.
Hydrolysis reaction- the breaking down of a large molecule into smaller ones
by the addition of water molecules.
Polymerisation- the process by which polymers form.
Each condensation of two monomers eliminates one molecule of water.
Amino acid +amino acid= dipeptide + water
Glycerol + 3 fatty acids = triglyceride + water
Carbohydrates
Carbohydrates are molecules which consist only of carbon, hydrogen and
oxygen and they are long chains of sugar units called saccharides. A single
monomer is called a monosaccharide with a pair of monomers being called a
disaccharide. Combining many monosaccharides results in the formation of a
polysaccharide. These are all joined together with a glycosidic bond formed in
a condensation reaction.
Carbon containing molecules are called organic molecules.
Monosaccharides
Glucose is a monosaccharide containing six carbon atoms in each molecule and
is the main substrate for respiration and it’s the main way carbohydrates are
transported around the body of animals. It has two isomers – alpha and beta
glucose.
Common monosaccharides include glucose, galactose
and fructose. These are typically sweet tasting, soluble
substances which have the general formula (CH2O)n where n can any number
from three to seven.
, Disaccharides:
Two monosaccharides can join together in a condensation reaction to form a
disaccharide. In this process a molecule of water is produced. The diagram
below shows the formation of a 1-4 glycosidic bond between two alpha
glucose molecules in order to form a molecule of maltose. In maltose, sucrose
and galactose the bond is always alpha 1-4 glycosidic bond.
Glucose + glucose = maltose
Glucose + fructose = sucrose
Glucose + galactose = lactose
Polysaccharides
Polysaccharides are formed from many glucose units joined together and
include:
- Glycogen and starch which are both formed by the condensation of
alpha glucose.
- Cellulose formed by the condensation of beta glucose.
Glycogen is the main energy storage molecule in animals and is formed from
many molecules of alpha glucose joined together by 1, 4 and 1, 6 glycosidic
bonds. It has a large number of branches meaning that energy can be released
quickly as enzymes can act simultaneously on these branches which is good for
animals with a high metabolic and respiratory rate as it can readily be broken
down into glucose and used in respiration. Moreover, it is a relatively large but
compact molecule, thus maximising the amount of energy it can store in a
small space. Finally being insoluble means it will not affect the water potential
of cells so doesn’t tend to draw water into the cell and cannot diffuse out of
cells. It is stored as small granules in the muscles and the liver
