Essential Molecules
Essential Molecules
Some important elements
Biological Molecules
Organisms are made from a huge variety of organic and
inorganic compounds.
The most important inorganic molecule is WATER.
The main organic molecules are:
1.
2.
3.
4.
Carbohydrates
Proteins
Lipids
Nucleic Acids
1. Carbohydrates
• These include sugars, starches, cellulose
and glycogen.
carbohydrate
molecule
one sugar
molecule
• Carbohydrates always contain the elements
carbon, hydrogen and oxygen.
They are divided into 3
categories, according to size:
– Monosaccharides – ‘simple sugars’,
eg. glucose and fructose
– Disaccharides – ‘double sugars’,
eg. sucrose and maltose
– Polysaccharides – ‘multiple sugars’,
eg. starch, glycogen and cellulose
Size and Function
• Sugars - are small molecules,
soluble in water, easy to
transport, making them ideal
sources of energy
• Polysaccharides – giant
molecules
eg. Starch and Glycogen have
compact, coiled and branched
molecules, making them ideal
stores of energy
Size and Function cont’d
eg. Cellulose molecules
have long straight
molecules, perfect
for forming
structural fibres
Uses of Carbohydrates in Living
Organisms
2. Proteins
Proteins, like carbohydrates, are made of long
chains of small molecules. In proteins, these
small molecules are not identical.
protein
molecule
one
amino
acid
Proteins are made up of chains of small
molecules called amino acids. There are
over 20 different kinds of amino acid.
Structure of Proteins
They contain the
elements carbon,
hydrogen, oxygen
and nitrogen (also
often sulfur and
phosphorus).
The subunits – amino
acids – can be joined
in any order and are
key to the large
variety of proteins.
Two amino acids join
together to form a
dipeptide. A chain of
amino acids is known as a
polypeptide.
Functions of Proteins in the
Human Body
• Enzymes are proteins that control metabolism (body
chemistry). There is a different enzyme for every
reaction.
• Antibodies are proteins that help us to fight disease
• Collagen and other strong proteins effectively hold us
together – connective tissues i.e. tendons, cartilage and
bones all owe their strength to collagen
• Blood clotting involves many different proteins
• Keratin is the protein that gives strength to hair, skin
and nails
3. Lipids
Lipids are a group of compounds that
include fats, oils and waxes. They all
contain the elements carbon, hydrogen
and oxygen. Importantly, they do not
mix with water.
There are 2 main types – Triglycerides
and Phospholipids.
Triglycerides
Triglycerides are made up of fat molecules
which contain fatty acids and glycerol.
fat
molecule
fatty
acids
glycerol
Triglycerides molecules have to be broken
down by the body so that they can be
used for energy storage.
Phospholipids
Are important in Biology as they form cell
membranes, which surround all cells. A
phospholipid molecule is similar to a
triglycerides except one fatty acid is
replaced by a phosphate group.
Functions of Lipids
•
•
•
•
•
•
Source of energy
Insulation
Protection
Buoyancy
Waterproofing
Cell membranes
4. Nucleic Acids
Are made up of chains of individual units
called nucleotides. These are
comprised of:
1. A Phosphate group
2. A sugar
3. A base – there are 5 of these:
CYTOSINE
THYMINE
ADENINE
GUANINE
URACIL
Structure and Function
The main function of nucleotides is the
formation of nucleic acids RNA and DNA,
which play vital roles in protein synthesis and
heredity.