A unique organelle for studying membrane biochemistry is the mitochondrion whose 
functionality depends on a coordinated supply of proteins and lipids. 
Mitochondria are capable of synthesizing several lipids autonomously such as 
phosphatidylglycerol, cardiolipin and in part phosphatidylethanolamine, 
phosphatidic acid and CDP-diacylglycerol. Other mitochondrial membrane lipids 
such as phosphatidylcholine, phosphatidylserine, phosphatidylinositol, sterols 
and sphingolipids have to be imported. The mitochondrial lipid composition, the 
biosynthesis and the import of mitochondrial lipids as well as the regulation of 
these processes will be main issues of this review article. Furthermore, 
interactions of lipids and mitochondrial proteins which are highly important for 
various mitochondrial processes will be discussed. Malfunction or loss of 
enzymes involved in mitochondrial phospholipid biosynthesis lead to dysfunction 
of cell respiration, affect the assembly and stability of the mitochondrial 
protein import machinery and cause abnormal mitochondrial morphology or even 
lethality. Molecular aspects of these processes as well as diseases related to 
defects in the formation of mitochondrial membranes will be described.