<P> Phosphatidylcholines (PC) are a class of phospholipids that incorporate choline as a headgroup . They are a major component of biological membranes and can be easily obtained from a variety of readily available sources, such as egg yolk or soybeans, from which they are mechanically or chemically extracted using hexane . They are also a member of the lecithin group of yellow - brownish fatty substances occurring in animal and plant tissues . Dipalmitoyl phosphatidylcholine (a.k.a. lecithin) is a major component of pulmonary surfactant and is often used in the L / S ratio to calculate fetal lung maturity . While phosphatidylcholines are found in all plant and animal cells, they are absent in the membranes of most bacteria, including Escherichia coli . Purified phosphatidylcholine is produced commercially . </P> <P> The name "lecithin" was originally defined from the Greek lekithos (λεκιθος, egg yolk) by Theodore Nicolas Gobley, a French chemist and pharmacist of the mid-19th century, who applied it to the egg yolk phosphatidylcholine that he identified in 1847 . Gobley eventually completely described his lecithin from chemical structural point of view, in 1874 . Phosphatidylcholines are such a major component of lecithin that in some contexts the terms are sometimes used as synonyms . However, lecithin extracts consist of a mixture of phosphatidylcholine and other compounds . It is also used along with sodium taurocholate for simulating fed - and fasted - state biorelevant media in dissolution studies of highly lipophilic drugs . </P>

Which of the following molecules is made in the synthesis of phosphatidylcholine