MACROMOLECULES 127 



V. LIPOPROTEINS 



The lipoproteins are macromolecules that are complexes of proteins 

 with simple or complex lipides. Complexes of steroids and their esters 

 and carotenoids and their esters with proteins are generally classed under 

 this heading. 



Lipoproteins are very widely distributed in the biosphere. They are 

 very large and very unstable macromolecules. They are found in all parts 

 of the cell. Certain authors maintain that the chlorophyll-proteins are 

 really chlorophyll-lipoproteins. Whatever the truth of this, the study of 

 lipoproteins has not progressed far. 



One of these substances, however, has been the subject of much exhaus- 

 tive study; this is the lipoprotein of mammalian blood plasma. It is a very 

 complex macromolecule made up of complex lipides, cholesterol, choles- 

 terol esters and polypeptide chains. 



REFERENCES 



GURD, F. R. N. (1954). Chemical Specificity in Biological Interactions. (A collection 

 of papers read by various authors, the principal theme being the formation 

 of complexes of proteins with metals and with other molecules.) Academic 

 Press, New York. 



Lemberg, R. and Legge, J. W. (1949). Hematin Compounds and Bile Pigments. 

 Inter-science, New York. 



Wyman, J., Jr. (1948). Heme proteins. Adv. Protein Chem., 4, 407-531. 



