192 APPENDIX 



galactolipines and lipines. Phospholipines are digilycerides in which the 

 third alcohol group is combined with phosphoric acid. Since phosphoric 

 acid is trivalent it can combine with two other substances. In lecithin 

 it combines with only one other substance, the'organic base, choline. The 

 phospholipines are unstable and are partly decomposed and oxidized by 

 extraction with hot solvents in the presence of air, and hence their com- 

 position has not been entirely settled in all cases. 



In galactolipines, galactose takes the place of glycerol. Lipines contain 

 nitrogen (but no carbohydrate or phosphoric acid. From fatty acids and 

 ammonia may foe prepared not only acid amides, but also amino acids 

 (lactic acid with NH„ and a dehydrating agent forms alanine). In the 

 mono-amino acids obtained from mammalian cells the NH 2 group is at- 

 tached to the carbon atom next to the COOH group. These acids are 

 called alpha amino acids. In the diamine acids, an additional NH 2 group 

 is attached to some other carbon atom of the chain. 



The amino acids have both acid and basic properties and are therefore 

 called amphoteric. In the diamino acids the basic property predominates. 

 Amino acids may be derived from dibasic acids, containing two COOH 

 groups and in this case the acid property markedly predominates. 



The proteins are compounds of amino acids in which the NH 2 group 

 of one molecule has reacted with the COOH group of another. The 

 complete structure of none of the proteins is known, but many amino 

 acids have been separated from the decomposition products, among which 

 are : The monoamine acids, amino acetic or glycine, aminopropionic or 

 alanine, amino isovalerianic or valine, and aminoisocaproic or leucine. 

 The dibasic amino acids are aspartic and glutamic acids. The diamino 

 acids are lysine, arginine, and diaminotrioxydodecoic acid. Cystine con- 

 tains two atoms of sulphur. Other amino acids contain cyclic compounds, 

 which will now 'be considered. 



Whereas in the compounds thus far considered the carbon atoms are 

 arranged in an open chain, in the cyclic compounds they are in the form 

 of a closed ring. The most important of these rings is the benzol ring 

 containing 6 carbon atoms. Although this ring has only 6 H atoms there 

 seem to be no double bonds between the carbon atoms, or if there are 

 double bonds they do not behave as the double bonds of the unsaturated 

 open chain compounds. In benzol, C H , each C atom is united to one 

 hydrogen atom.. The substitution of one or more hydrogen atoms by 

 other atoms or groups gives rise to a host of compounds. When only 

 one hydrogen is substituted it is immaterial which carbon atom it is 

 attached to, but by its presence the other carbon atoms lying at different 

 distances from the first one are designated as ortho, rneta and para, and 

 groups that may subsequently be attached to them are in the ortho, meta, 

 or para position. 



Of the mono-substitution products of benzol we have aniline, C a H 5 NH 2 , 

 benzol-sulphonic acid, CH5SO3H, phenol, CHkOH, toluol, CHjCHs, 

 benzyl alcohol, C 6 H B 'CH 2 OH, benzaldehyde, CoH/CHO, and benzoic acid, 

 C 6 H 5 OOOH. 



Of the di-substitution products we have catechol (ortho-hydroxyphenol), 

 resorcinol (meta-hydroxyphenol), hydroquinone (para-hydroxyphenol), 

 salicylic acid (ortho-hydroxy benzoic aoid), and tyrosin (para-hydroxy- 

 phenylalanine) . Tyrosin is an amino acid found in proteins. 



Some tri-sufostitution products are pyrogallol, homiogentisic acid, picric 

 acid and adrenaline. _ Adrenaline is secreted by cells of the adrenal 

 medulla and is a specific stimulant (or in some cases inhibitor) of smooth 

 muscle cells, although its action is supposed not to be on the whole cell 

 surface but on a theoretical receptor substance. 



The pyrrol ring contains 1 nitrogen and 4 carbon atoms and is con- 

 tained in proline and oxyproline, amino acids found in proteins. Trypto- 

 phane, another amino acid found in proteins, contains a combination of 



