*2.4.3 Lipid microdomains*

Membranes are not even in composition throughout. Instead, they can have areas of differential lipid composition such as lipid rafts. Lipid rafts are generally more tightly packed (less fluid) than neighboring membrane material and their edges are usually rich in sphingolipids and cholesterol [11, 15, 17, 18]. Lipid rafts, because of their differential lipid composition, can act as scaffolds for non-clathrinmediated internalization dynamics [11, 15, 17, 18].

While no specific lipid microdomains have been identified as characteristic of autophagosome membranes, it is known that lipid rafts associated with the endoplasmic reticulum and mitochondria can contribute to autophagosome formation from these lipid sources [13, 14].
