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…. 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). If there is a job to be done in the molecular world of cells, usually that job is done by a protein. 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

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