Brent Cornell

    
Organic Compounds

An organic compound is a compound that contains carbon and is found in living things

• Exceptions include carbides (e.g. CaC₂), carbonates (CO₃^2–), oxides of carbon (CO, CO₂) and cyanides (CN^–)  

Carbon 

Carbon forms the basis of organic life due to its ability to form large and complex molecules via covalent bonding

Carbon atoms can form four covalent bonds, with bonds between carbon atoms being particularly stable (catenation) 

• These properties allows carbon to form a wide variety of organic compounds that are chemically stable

Schematic of a Carbon Atom

    
Main Classes of Carbon Compounds

There are four principle groups of organic compounds that contribute to much of the structure and function of a cell

Carbohydrates

• Most abundant organic compound found in nature, composed primarily of C,H and O atoms in a common ratio – (CH₂O)_n
• Principally function as a source of energy (and as a short-term energy storage option)
• Also important as a recognition molecule (e.g. glycoproteins) and as a structural component (part of DNA / RNA)

Lipids

• Non-polar, hydrophobic molecules which may come in a variety of forms (simple, complex or derived)
• Lipids serve as a major component of cell membranes (phospholipids and cholesterol)
• They may be utilised as a long-term energy storage molecule (fats and oils)
• Also may function as a signalling molecule (steroids)

Nucleic Acids

• Genetic material of all cells and determines the inherited features of an organism
• DNA functions as a master code for protein assembly, while RNA plays an active role in the manufacturing of proteins

Proteins

• Make over 50% of the dry weight of cells; are composed of C, H, O and N atoms (some may include S) 
• Major regulatory molecules involved in catalysis (all enzymes are proteins)
• May also function as structural molecules or play a role in cellular signalling (transduction pathways)

Main Classes of Organic Compounds in Cells