BIOLOGICAL MOLECULES
Biological Molecules
• Biological molecules (Biomolecules) are important in
organisms to build structures and for use in metabolic
reactions.
• Large biological molecules (macromolecules) are made
when many smaller repeating subunits (also known as
monomers), bind together.
• When macromolecules are made of long chains of monomers
held together by chemical bonds, they are known as
polymers (poly: many). Examples are polysaccharides.
• All molecules found within living things can be grouped
into one of three categories;
• Carbohydrate
• Protein and
• Lipids
• They are comprised of long chains which are broken
down into simpler subunits during digestion.
Biological Molecules (Cont’d)
• These molecules are examples of organic compounds as they
contain the element, Carbon. The table below indicates other
elements that they share.
BIOLOGICAL
MOLECULE
CARBOHYDRATE
CARBON
HYDROGEN
OXYGEN
NITROGEN
X
PROTEIN
LIPID
X
CARBOHYDRATES
• Carbohydrates comprise many sugar molecules
containing carbon, hydrogen and oxygen atoms. They are
made up of sugar molecules joined together in long chains.
• A single sugar is called a monosaccharide. Monosaccharides
are the simplest form of sugar, and they cannot be broken
down any further.
• Disaccharides on the other hand are two sugar molecules
bonded. For example, sucrose is a disaccharide as it consists
of two monosaccharides (glucose and fructose) bonded
together
CARBOHYDRATES (Cont’d)
• Glucose is a small sugar molecule. When many glucose
molecules bind together in a chain, cellulose, starch and
glycogen can be made. They are referred to as
polysaccharides.
• Cellulose is used for structure and makes up plant cell walls,
whereas starch and glucose are stored in cells and used in
respiration to provide energy for the organism.
• Starch is stored in plants while glycogen is stored in animals
Food sources for Carbohydrates
MONOSACCHARIDES
DISACCHARIDES
POLYSACCHARIDES
They are soluble
They are soluble
They are insoluble
Sugar with one carbon ring
Sugar with two carbon rings
Sugar with many carbon rings
Glucose: Fruit, berry, sweet
corn, grapes
Sucrose: sugar cane, jams,
Starch: grains, vegetables esp.
sugar beet (granulated, brown, root & tubers, legumes, bread,
confectioner), candy
rice, flour, green banana,
pasta,
Lactose: Milk, Milk products
Glycogen: Glucose stored in
Maltose: Malt, Cereal products liver and muscles, crackers
Fructose: Fruit, honey, soft
drinks
Galactose: They do not occur
naturally (in free forms). It is
the product of digestion of
milk.
Cellulose: Wheat bran, wholegrain cereals, green and leafy
vegetables,
LIPIDS
• Lipids are diverse groups of
organic compounds that
play crucial roles in living
organisms.
• Fats are a solid form of a
group of molecules called
lipids. When lipids are liquid,
they are referred to as Oils.
• They are hydrophobic in
nature.
LIPIDS (Cont’d)
• Fats and Oils are formed
from Carbon, Hydrogen
and Oxygen.
• A molecule of fat or oil is
made up of three
molecules of an organic
acid called a fatty acid,
combined with one
molecule of glycerol.
A Fat Molecule
LIPIDS (Cont’d)
• Lipids form part of the cell membrane and the internal
membranes of the cell. For example, nuclear membrane.
• Fats are a store of energy providing double the energy that
carbohydrates and proteins do.
• Fats play a variety of roles in living organisms such as
energy, insulation, waterproofing, structure and
protection around delicate organs in the body.
PROTEINS
• Proteins are polymers
(macromolecules) made from long
chains of amino acids
(monomers).
• They are made up of Carbon,
Hydrogen, Oxygen, Nitrogen (and
sometimes Sulphur)
• They are the most abundant
organic molecules in the living
system. They occur in every part of
the cell, and they form 50% of
cellular dry weight.
• These are molecules essential for
growth and repair. They can be used
as a source of energy if lipids and
carbohydrate levels are low.
• Some proteins contribute to the
structure of the cell e.g., the cell
membrane, mitochondria,
ribosomes and chromosomes. These
proteins are called structural
proteins.
• After digestion, amino acids are
absorbed into the bloodstream and
brought to cells that reassemble them
into proteins needed by the body (e.g.
enzymes).
• Different arrangements of amino acids make up different proteins
and form different shapes. Examples are Enzymes.
• Each enzyme’s site has a specific shape, allowing it to bind to a
specific substrate molecule to catalyze metabolic reactions.
• Antibodies also have a specific shape formed by a specific
sequence of amino acids. This allows them to bind to antigens on
foreign pathogens to kill them
References
• https://www.brainkart.com/article/Classification-ofCarbohydrates_32689/
• https://www.bbc.co.uk/bitesize/guides/zs9krwx/revision/1
• https://www.thesciencehive.co.uk/biological-molecules-gcse