ABSTRACT
Unesterified alcohols that are components of lipid extracts inevitably contain carbon chains that are sufficiently long to be quite hydrophobic. Polyisoprenoid alcohols in the form of dolichols are present in most tissues of most eukaryotic organisms. The most common lipid-soluble phenols are the tocopherols. They are found in plant and animal systems where they appear to fulfill an anti-oxidant role. Small quantities of paraffinic aldehydes and ketones can be found in plant waxes, insect cuticles and in micro-organisms. They are often responsible for the flavors and odors of foods. Some branched and cyclic ketones show pheromone activity Important carotenoids carrying keto groups are astaxanthin and fucoxanthin. All of the major hydrophobic quinones of natural origin contain polyisoprenoid side-chains which anchor them in membranes where the quinone performs its function. This involves the transfer of electrons involving reversible reduction and oxidation, probably through the corresponding quinol.
