#membrane curvature

Plasma Membrane

Which of the following influences membrane curvature?

Intrinsic lipid shape contributes substantially to membrane bending energy as described by Helfrich elastic theory and packing parameter concepts. Phospholipids with small headgroup relative to bulky unsaturated tail volume possess negative intrinsic curvature favoring concave bending of monolayer. Phosphatidylethanolamine possesses ethanolamine headgroup substantially smaller than choline of phosphatidylcholine conferring cone shape with packing parameter greater than one, preferring inverted hexagonal HII phases under stress and reducing bilayer stability. Enrichment of PE in cytoplasmic lea

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 10: Membrane Curvature and PE Shape.

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Glycolipid and Phospholipid

Which lipid modification helps maintain membrane curvature?

Maintenance high curvature membranes such as thirty nanometer synaptic vesicles tubular ER sheets requires conical lipids complementing protein scaffolds BAR ENTH and reticulons. Phosphatidylethanolamine ethanolamine headgroup cross section smaller than diacylglycerol tail volume adopts molecular cone favoring negative mean curvature concave cytosolic leaflet facilitating fission fusion stalk formation hemifusion diaphragm expansion. Synthesis via Kennedy pathway CDP ethanolamine ethanolamine phosphotransferase EPT1 and mitochondrial phosphatidylserine decarboxylase PSD converting PS PE enrich

Ref: Vance JE & Tasseva G., Biochim Biophys Acta 2013, PE cone shape maintains curvature and fusion.

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Properties of Plasma Membrane

What is the primary determinant of lipid bilayer curvature?

Spontaneous curvature stems from imbalance between optimal headgroup repulsion and hydrocarbon chain pressure described by Israelachvili packing parameter P equals v divided by a times l. When headgroup area a large relative to volume v molecule resembles inverted cone P less than one yielding positive curvature forming micelles as lysophosphatidylcholine with one chain generating outward bulges. Small headgroup like PE PA DAG yields cone P greater than one favoring negative curvature invaginations and HII tubes needed for fusion fission. PC sphingomyelin balanced a and v give cylinder P about

Ref: McMahon & Gallop, Nature 2005, Mechanisms membrane curvature determinants headgroup size.

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Properties of Plasma Membrane

Which of the following lipid modifications increases curvature in membranes?

Membrane bending energy is governed by molecular geometry quantified as shape parameter defined as volume over area times length. Phosphatidylethanolamine possesses small ethanolamine headgroup about zero point two eight square nanometers versus larger hydrocarbon volume due to two acyl chains, creating conical shape with parameter greater than one favoring negative spontaneous curvature typical of inner leaflet concave tubules and fusion stalk intermediates. Enrichment of PE in cytoplasmic leaflet at SNARE assembly sites reduces hydration repulsion and elastic cost of merging outer leaflets f

Ref: Chernomordik & Kozlov, Nature Structural Biology 2003, PE and membrane curvature in fusion.

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Properties of Plasma Membrane

Which phospholipid is conical in shape and contributes to membrane curvature?

Intrinsic lipid curvature concept explains membrane remodeling during endocytosis exocytosis and organelle shaping. Lipid shape analyzed via Israelachvili packing parameter p equals v over a times l where v volume tail a head area l length: cylindrical p approximately one forms flat bilayers as phosphatidylcholine with two acyl chains head size similar to tail cross-section; conical p greater than one small head large tails such as phosphatidylethanolamine and diacylglycerol tends negative curvature monolayers bending toward water favoring inverted hexagonal HII phase; inverted conical p less

Ref: McMahon and Gallop, Membrane Curvature and PE Conical Shape, Nature 2005.

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