An overview of the important classes of organic molecules
The major classes of organic compounds are Proteins,
Carbohydrates, Lipids and Nucleic acids.
•All of these organic molecules always contain the elements Carbon (C),
Hydrogen (H) and Oxygen (O). Proteins contain Nitrogen as well, and
sometimes sulfur. Nucleic acids have C, H, O, N and phosphorus (P).
Each of the above compounds are complex macromolecules called
polymers which are made up of smaller sub units called monomers.
This slide show will take you through each class of compound.
Proteins….
If there is a job to be
done in the molecular
world of our cells,
usually that job is done
by a protein.
CATALASE
An enzyme which removes Hydrogen
peroxide from your body so it does not
become toxic
A protein hormone which helps to regulate your
blood sugar levels
Examples of proteins include: hormones acting as messengers;
enzymes speeding up reactions; cell receptors acting as
‘antennae’; antibodies fighting foreign invaders; membrane
channels allowing specific molecules to enter or leave a cell; they
make up the muscles for moving; let you grow hair, ligaments and
fingernails; and let you see (the lens of your eye is pure
crystallised protein).
Proteins….
 Proteins are large complex molecules
built of monomers called amino acids.
The amino acids are held together by
peptide bonds, so proteins are known as
polypeptides.
 There are usually multiple peptide
chains joined together eg. Haemoglobin
has 4 polypeptide chains comprising it.
 The polypeptide chains are then folded
into a particular shape unique to that
type of protein
 Proteins can be fibrous or globular,
fibrous proteins normally are involved in
body structures (structural proteins),
globular proteins are normally
biochemical.
Globular Proteins
 The globular proteins have a number of biologically important
roles. They include:
 Cell motility – proteins link together to make filaments to make movement





possible.
Organic catalysts in biochemical reactions – enzymes that speed up
reactions.
Regulatory proteins – hormones transcription factors.
Membrane proteins – MHC markers, protein channels, gap junctions.
Defence against pathogens – poisons/toxins, antibodies.
Transport and storage – haemoglobin, myosin.
Structural Proteins
 Hair (keratin)
 Fingernails (keratin)
 Skin (collagen)
 Muscles (myosin, etc)
 Cartilage (glycoprotein: proteins attached to
carbohydrates
 Ligaments (collagen plus glycoproteins)
 Eye cornea (collagen/keratin)
Carbohydrates
Another class of compounds that use carbon, oxygen, and
hydrogen are the carbohydrates
Below are some examples of carbohydrates ( Sugars, starch, cellulose and
glycogen):
• Glycogen is a complex polysaccharide created in animals for the purpose of
storing chemical energy. The small black granules (dots) are glycogen.
• Starch is the long term energy storage molecule for most plants.
Nucleic acids
 Very large macromolecules concerned with the storage and
transmission of inherited information and protein synthesis.
 Made up of repeating units called nucleotides.
 Two types: deoxyribonucleic acid (DNA) and ribonucleic
acid (RNA).
Lipids
 Lipids (oils and fats) are another class of organic compounds built from
oxygen, hydrogen, and carbon.
 Lipids have a structural role, for example the plasma membrane is
composed to a large part by phospholipids , a biochemical role, for
example some hormones are steroids, and are the long term energy
storage compound for all animals
 Lipids are composed of the subunits fatty acids and glycerol
This diagram represents a
triglyceride, a simple and
common form of fat