The 16-to 18-carbon fatty acid (R1) is amide linked to ornithin, while the second fatty acid (R2), sometimes with a cyclopropane ring, esterižes the acid function of the amino acid.

These amino lipids discovered in a freshwater alga (Ochromonas danica) were also described in a halotolerant alga (Duniliella parva) (Evans et al., 1982). They consist of a diacylglycerol moiety ether linked on the sn-3 carbon of glycerol to an organic base derived from betain, hence their name-betain lipids. The most frequent polar headgroup is the 4′-(N,N,N-trimethyl)-homoserine (Figure 4.3).