What lipids are found in the plasma membrane?

Membrane lipids are amphipathic, which ways that they have a polar or hydrophilic terminate and a non-polar or hydrophobic terminate. In aqueous mediums, membrane lipids spontaneously organize into bilayers with the polar ends oriented towards, and the non-polar ends oriented away from, the solution. The bilayer closes in on itself to avoid complimentary edges with water. These basic structural properties of plasma membranes enable them to carry out their central functions. For example, the propensity of membrane lipids to class a thermodynamically stable, airtight lipid bilayer structures renders them stability and encourages the formation of closed subcellular compartments. It too enables the spontaneous repair of minor tears in the membrane, which prevents material leaking out of the jail cell or organelles. Furthermore, the hydrophobic interior of membranes serves as a barrier to water soluble molecules but allows sure lipid soluble molecules to passively diffuse through. Membranes are therefore selectively permeable structures; a holding that helps to prevent leakage and protect the cell from the passive entry of many toxins.

Phosphoglycerides have a hydrophilic polar head and a hydrophobic fatty acid tail. The limerick and length of the hydrocarbon tail is somewhat diverse and is reported to range from fourteen carbons to 24 carbons. Chemical modification to the inositol band occurs in the conversion of phosphatidylinositol to other phosphoinositides.

Membrane lipids are highly diverse, with a typical membrane containing more than 100 species of lipids. These lipids vary in their structure and extent of saturation of the fat acyl bondage.

There are iii major classes of membrane lipids – the phosphoglycerides, sphingolipids and sterols.

What are phospholipids?

The phosphoglycerides and sphingolipids tin be combined every bit 1 class, the phospholipids. These are the classical membrane lipid, formed of a polar head group and 2 hydrophobic fat acrid tails. The fat acrid tails typically contain betwixt 14-24 carbon atoms. 1 of the 2 tails is unsaturated and therefore contains one or more cis-double bonds, which creates a small kink in the tail. The other tail is saturated, without whatever cis-double bonds and remains direct. Variations in the length and saturation of the fatty acid tail affect how tightly phospholipids are able to pack against each other, leading to contradistinct membrane fluidity. Linking the polar head grouping to the fat acid tail is a backbone made up of either glycerol or sphingosine. The different backbone molecule differentiates between the classes of phospholipid.

How are phosphoglycerides structurally and biochemically unlike from sphingolipids?

Phosphoglycerides have a polar caput grouping esterified to one of 3 glycerol hydroxyl groups, and two hydrophobic fatty acid tails esterified to the remaining ii hydroxyl groups of the glycerol backbone. The polar head group is composed of a phosphate group linked to choline, ethanolamine, serine or inositol. These form phosphatidyl choline (PC), phosphatidyl ethanolamine (PE), phosphatidyl serine (PS) and phosphatidylinositol (PI) respectively.

Sphingolipids, on the other hand, accept a backbone formed from sphingosine, an amino alcohol with a long hydrocarbon chain; a less abundant class of membrane lipids. Ceramide is a simple sphingolipid which has a hydrophobic fat acid tail linked to the amino group of the sphingosine. The esterification of boosted groups to the last hydroxyl grouping of the sphingosine backbone gives rise to other types of sphingolipids. For instance, sphingomyelin has a polar phosphoryl choline head group and glycolipids have a sugar group. The sugar group of glycolipids can be a unproblematic sugar or an oligosaccharide forming cerebrosides and gangliosides respectively.

Sterols are smaller than phospholipids. They have a single polar hydroxyl head group attached to a rigid steroid band construction and a curt non-polar hydrocarbon tail. Cholesterol is the major sterol component of fauna jail cell membranes. Different sterols are constitute in other eukaryotic cell membranes. Yeast and fungi use ergosterol, while plants use sitosterol and stigmasterol. However, prokaryotic cell membranes substantially contain no sterols. Sterols insert into the lipid bilayer with their hydroxyl head groups oriented with the phospholipid polar groups. This aligns the rigid ring construction of the sterol with the phospholipid hydrocarbon tail, which decreases phospholipid mobility. This stiffening consequence also reduces the h2o-soluble permeability of the bilayer but does not affect membrane fluidity.

  • What is the plasma membrane?
  • What types of proteins are found in the plasma membrane?
  • How do mechanically-gated ion channels facilitate mechanotransduction?
  • How do lipid bilayer components move?
  • Why are membrane lipids asymmetrical?
  • What are membrane reservoirs?
  • What is membrane curvature?
  • What is membrane trafficking?

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