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. 2019 May 1;20(9):2167. doi: 10.3390/ijms20092167

Figure 3.

Figure 3

Membrane homeostasis and circuits of lipids between organelles. (a) Lipid bilayers can form a number of different structures upon their composition in PL species. Some examples of lipid shapes and their influence on membrane structure are shown. Lipids with a small polar head (blue), such as PtdEtn, have a molecular shape that resembles a truncated cone. They induce a negative curvature strain. Lipids with a bulky polar head and only one acyl chain (e.g., lysophospholipids, green) have a molecular shape similar to an inverted cone and induce a positive curvature strain in membranes. Lipids such as PtdCho have similar cross-sectional areas for the polar head and hydrophobic region and resemble cylinders (red). They form lamellar phases, with no curvature strain. Not to scale. Adapted from [113]. (b) Mechanisms of lipid homeostasis maintenance between cell compartments. Chol: cholesterol; ER: endoplasmic reticulum; MCS: membrane contact sites; LTPs: lipid transfer proteins; PM: plasma membrane; PtdCho: phosphatidylcholine; PtdEtn: phosphatidylethanolamine.