A report on Phospholipid and Lipid bilayer

Phospholipid arrangement in cell membranes.
This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.
Phosphatidylcholine is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons.
The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer.
Phospholipid bilayers are the main structural component of the cell membranes.
Schematic cross sectional profile of a typical lipid bilayer. There are three distinct regions: the fully hydrated headgroups, the fully dehydrated alkane core and a short intermediate region with partial hydration. Although the head groups are neutral, they have significant dipole moments that influence the molecular arrangement.
TEM image of a bacterium. The furry appearance on the outside is due to a coat of long-chain sugars attached to the cell membrane. This coating helps trap water to prevent the bacterium from becoming dehydrated.
Diagram showing the effect of unsaturated lipids on a bilayer. The lipids with an unsaturated tail (blue) disrupt the packing of those with only saturated tails (black). The resulting bilayer has more free space and is, as a consequence, more permeable to water and other small molecules.
Illustration of a GPCR signaling protein. In response to a molecule such as a hormone binding to the exterior domain (blue) the GPCR changes shape and catalyzes a chemical reaction on the interior domain (red). The gray feature is the surrounding bilayer.
Transmission Electron Microscope (TEM) image of a lipid vesicle. The two dark bands around the edge are the two leaflets of the bilayer. Historically, similar images confirmed that the cell membrane is a bilayer
Human red blood cells viewed through a fluorescence microscope. The cell membrane has been stained with a fluorescent dye. Scale bar is 20μm.
3d-Adapted AFM images showing formation of transmembrane pores (holes) in supported lipid bilayer
Illustration of a typical AFM scan of a supported lipid bilayer. The pits are defects in the bilayer, exposing the smooth surface of the substrate underneath.
Structure of a potassium ion channel. The alpha helices penetrate the bilayer (boundaries indicated by red and blue lines), opening a hole through which potassium ions can flow
Schematic illustration of pinocytosis, a type of endocytosis
Exocytosis of outer membrane vesicles (MV) liberated from inflated periplasmic pockets (p) on surface of human Salmonella 3,10:r:- pathogens docking on plasma membrane of macrophage cells (M) in chicken ileum, for host-pathogen signaling in vivo.
Schematic showing two possible conformations of the lipids at the edge of a pore. In the top image the lipids have not rearranged, so the pore wall is hydrophobic. In the bottom image some of the lipid heads have bent over, so the pore wall is hydrophilic.
Illustration of lipid vesicles fusing showing two possible outcomes: hemifusion and full fusion. In hemifusion, only the outer bilayer leaflets mix. In full fusion both leaflets as well as the internal contents mix.
Schematic illustration of the process of fusion through stalk formation.
Diagram of the action of SNARE proteins docking a vesicle for exocytosis. Complementary versions of the protein on the vesicle and the target membrane bind and wrap around each other, drawing the two bilayers close together in the process.

They can form lipid bilayers because of their amphiphilic characteristic.

- Phospholipid

Biological bilayers are usually composed of amphiphilic phospholipids that have a hydrophilic phosphate head and a hydrophobic tail consisting of two fatty acid chains.

- Lipid bilayer
Phospholipid arrangement in cell membranes.

5 related topics with Alpha

Overall

Illustration of a Eukaryotic cell membrane

Cell membrane

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Biological membrane that separates the interior of all cells from the outside environment (the extracellular space) and protects the cell from its environment.

Biological membrane that separates the interior of all cells from the outside environment (the extracellular space) and protects the cell from its environment.

Illustration of a Eukaryotic cell membrane
Comparison of Eukaryotes vs. Prokaryotes
Examples of the major membrane phospholipids and glycolipids: phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn), phosphatidylinositol (PtdIns), phosphatidylserine (PtdSer).
A detailed diagram of the cell membrane
Illustration depicting cellular diffusion
Diagram of the arrangement of amphipathic lipid molecules to form a lipid bilayer. The yellow polar head groups separate the grey hydrophobic tails from the aqueous cytosolic and extracellular environments.
Alpha intercalated cell
Diagram of the Cell Membrane's structures.

The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols (a lipid component) interspersed between them, maintaining appropriate membrane fluidity at various temperatures.

The cell membrane consists of three classes of amphipathic lipids: phospholipids, glycolipids, and sterols.

Structures of some common lipids. At the top are cholesterol and oleic acid. The middle structure is a triglyceride composed of oleoyl, stearoyl, and palmitoyl chains attached to a glycerol backbone. At the bottom is the common phospholipid phosphatidylcholine.

Lipid

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Biomolecule that is soluble in nonpolar solvents.

Biomolecule that is soluble in nonpolar solvents.

Structures of some common lipids. At the top are cholesterol and oleic acid. The middle structure is a triglyceride composed of oleoyl, stearoyl, and palmitoyl chains attached to a glycerol backbone. At the bottom is the common phospholipid phosphatidylcholine.
I2 - Prostacyclin (an example of a prostaglandin, an eicosanoid fatty acid)
LTB4 (an example of a leukotriene, an eicosanoid fatty acid)
Example of an unsaturated fat triglyceride (C55H98O6). Left part: glycerol; right part, from top to bottom: palmitic acid, oleic acid, alpha-linolenic acid.
Phosphatidylethanolamine
Sphingomyelin
Chemical structure of cholesterol.
Prenol lipid (2E-geraniol)
Structure of the saccharolipid Kdo2-lipid A. Glucosamine residues in blue, Kdo residues in red, acyl chains in black and phosphate groups in green.
Self-organization of phospholipids: a spherical liposome, a micelle, and a lipid bilayer.

Non-polar solvents are typically hydrocarbons used to dissolve other naturally occurring hydrocarbon lipid molecules that do not (or do not easily) dissolve in water, including fatty acids, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, and phospholipids.

Glycerophospholipids, usually referred to as phospholipids (though sphingomyelins are also classified as phospholipids), are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and cell signaling.

Phospholipids, such as this glycerophospholipid, have amphipathic character.

Amphiphile

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Chemical compound possessing both hydrophilic (water-loving, polar) and lipophilic (fat-loving) properties.

Chemical compound possessing both hydrophilic (water-loving, polar) and lipophilic (fat-loving) properties.

Phospholipids, such as this glycerophospholipid, have amphipathic character.
Cross-section view of the structures that can be formed by biological amphiphiles in aqueous solutions. Unlike this illustration, micelles are usually formed by non-biological, single-chain, amphiphiles, soaps or detergents, since it is difficult to fit two chains into this shape.
The lipid bilayer, the material that makes up cell membranes.

The phospholipid amphiphiles are the major structural component of cell membranes.

They arrange themselves into lipid bilayers, by forming a sheet composed of two layers of lipids.

An example of an ATP-dependent flippase in the ABC transporter family, isolated from C. jejuni. The two polypeptide chains in the homodimer structure are shown in red and blue. The extracellular surface is oriented at the top of the image and the ATP-binding domains are located at the bottom, on the cytosolic side.

Flippase

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Flippases (rarely spelled flipases) are transmembrane lipid transporter proteins located in the membrane which belong to ABC transporter or P4-type ATPase families.

Flippases (rarely spelled flipases) are transmembrane lipid transporter proteins located in the membrane which belong to ABC transporter or P4-type ATPase families.

An example of an ATP-dependent flippase in the ABC transporter family, isolated from C. jejuni. The two polypeptide chains in the homodimer structure are shown in red and blue. The extracellular surface is oriented at the top of the image and the ATP-binding domains are located at the bottom, on the cytosolic side.

They are responsible for aiding the movement of phospholipid molecules between the two leaflets that compose a cell's membrane (transverse diffusion, also known as a "flip-flop" transition).

The possibility of active maintenance of an asymmetric distribution of molecules in the phospholipid bilayer was predicted in the early 1970s by Mark Bretscher.

Micrograph of rough endoplasmic reticulum network around the nucleus (shown in the lower right-hand area of the picture). Dark small circles in the network are mitochondria.

Endoplasmic reticulum

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The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding.

The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding.

Micrograph of rough endoplasmic reticulum network around the nucleus (shown in the lower right-hand area of the picture). Dark small circles in the network are mitochondria.
1 Nucleus
2 Nuclear pore
3 Rough endoplasmic reticulum (RER)
4 Smooth endoplasmic reticulum (SER)
5 Ribosome on the rough ER
6 Proteins that are transported
7 Transport vesicle
8 Golgi apparatus
9 Cis face of the Golgi apparatus
10 Trans face of the Golgi apparatus
11 Cisternae of the Golgi apparatus
3D rendering of endoplasmic reticulum
A 2-minute animation showing how a protein destined for the secretory pathway is synthesized into the rough endoplasmic reticulum, which appears at the upper right approximately halfway through the animation.
Electron micrograph showing smooth ER (arrow) in mouse tissue, at 110,510× magnification.
Skeletal muscle fiber, with sarcoplasmic reticulum colored in blue.
Ca2+-antagonized transport into the endoplasmic reticulum (CaATiER) model

The phospholipid membrane encloses the cisternal space (or lumen), which is continuous with the perinuclear space but separate from the cytosol.

It synthesizes lipids, phospholipids, and steroids.