208 ALBUMINOIDS 



VI. Gliadins, e.g., wheat gliadin, hordein, zein ; soluble in 70 



to 80 per cent alcohol. 



VII. Phosphoproteins, e.g., caseinogen, vitellin. 

 VIII. Scleroproteins, e.g., keratin, gelatin, elastin, fibroin. 

 IX. Conjugated proteins, e.g., 



(i) Nucleoproteins, nucleic acid with protein. 



(ii) Chromoproteins, colouring substance with protein, e.g.* 



haemoglobin. 



(iii) Glucoproteins, carbohydrate with protein, e.g., mucin. 

 X. Protein derivatives 



(i) Metaproteins, e.g., acid albumin, alkali albumin. 



(ii) Proteoses, e.g., caseose, albumose, globulose. 



(iii) Peptones, e.g., fibropeptone. 



(iv) Polypeptides, e.g., glycyl-alanine, leucyl-glutamic acid. 



Chiefly by the labours of Fischer and his pupils during the last 

 twelve years, it has been shown that the protein molecules are built 

 up of a series of amino acids. The following is a list of the chief of 

 these compounds which have been derived from the hydrolysis of 

 proteins : 



Mono-amino-monocarboxylic acids. 



1. Glycine (Glycocoll) = amino-acetic acid, C i; H 5 NO.,, 



CH 2 (NH 2 ).COOH 



2. Alanine = a-amino-propionic acid, C 3 H 7 NO 2 , 



CH 3 .CH(NH 2 ).COOH 



3. Valine = a-amino-isovalerianic acid, C 5 H n N(X, 



(CH 3 ) 2 CH.CH(NH 2 ).COOH 



4. Leucine = a-amino-isocaproic acid, C 6 H 13 NO 9 , 



(CH 3 ) 2 CH.CH 2 .CH(NH 2 ).COOH 



5. Isoleucine = a-amino- /^methyls-ethyl propionic acid, C 6 H 13 N0 2> 



(CH 3 )(C 2 H 5 )CH.CH(NH 2 ).COOH 



6. Phenylalanine = /?-phenyl-a-amino-propionic acid, C 9 H n N<X, 



C 6 H 6 .CH 2 .CH(NH a ).COOH 



7. Tyrosine = ^8-para-hydroxyphenyl-a-amino-propionic acid, 



.C 9 H n N0 3 , 

 HO.C 6 H 4 .CH 2 .CH(NH 2 ).COOH 



8. Serine = /2-hydroxy-a-amiho-propionic acid, C 3 H 7 N0 3 , 



CH 2 (OH).CH(NH 2 ).COOH 



9. Cysteine = /3-sulph-hydro-a-amino-propionic acid, C 3 H~NO 2 S, 



CH 2 (SH).CH(NH 2 ).COOH 



Mono-amino-dicarboxylic acids. 



10. Aspartic acid = amino-succinic acid, C 4 H 7 NO 4 , 



COOH.CH 2 .CH(NH 2 ).COOH 



11. Glutamic acid = a-amino-glutaric acid, C,H 9 NO 4 , 



COOH.CH 2 .CH 2 .CH(NH 2 ).COOH 



