Food Lipids: Chemistry, Nutrition, and Biotechnology

2
Chemistry and Function
of Phospholipids
MARILYN C. ERICKSON
The University of Georgia, Griffin, Georgia
I. INTRODUCTION
Phospholipids can generally be regarded as asymmetrical phosphoric acid diesters
comprising chemical bonds of three types: C-C bonds, ester bonds, and phosphoester
bonds. While hydrolysis is inherent to the ester and phosphoester bonds, other physical
and chemical reactions associated with phospholipids are dictated by the kind
of head group and by the chain length and degree of unsaturation of the constituent
aliphatic moieties. These activities constitute the focus of this chapter. In addition,
the ramifications of phospholipids’ amphiphilic nature and their propensity to aggregate
as bilayers will be discussed in relation to their functional role in foods.
II. PHOSPHOLIPID CLASSIFICATION
Phospholipids are divided into two main classes depending on whether they contain
a glycerol or a sphingosyl backbone (Fig. 1). These differences in base structure
affect their chemical reactivity.
Glycerophospholipids are named after and contain structures that are based on
phosphatidic acid. The moeity attached to the phosphate includes nitrogenous bases
or polyols. Sphingolipids are lipids that contain sphingosine (trans-D-erythro-1,3dihydroxy-2-amino-4-octadecene)
or a related amino alcohol. Although the most
common sphingophospholipid, sphingomyelin, represents a major lipid in certain
membranes of animals, it is of minor importance in plants and probably is absent
from bacteria.
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.