A report on Lipid bilayer, Cell membrane and Phospholipid

This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.
Illustration of a Eukaryotic cell membrane
Phospholipid arrangement in cell membranes.
The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer.
Comparison of Eukaryotes vs. Prokaryotes
Phosphatidylcholine is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons.
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.
Examples of the major membrane phospholipids and glycolipids: phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn), phosphatidylinositol (PtdIns), phosphatidylserine (PtdSer).
Phospholipid bilayers are the main structural component of the cell membranes.
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.
A detailed diagram of the cell membrane
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 depicting cellular diffusion
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.
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.
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
Alpha intercalated cell
Human red blood cells viewed through a fluorescence microscope. The cell membrane has been stained with a fluorescent dye. Scale bar is 20μm.
Diagram of the Cell Membrane's structures.
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.

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.

- Cell membrane

The cell membranes of almost all organisms and many viruses are made of a lipid bilayer, as are the nuclear membrane surrounding the cell nucleus, and membranes of the membrane-bound organelles in the cell.

- Lipid bilayer

Phospholipids are a key component of all cell membranes.

- Phospholipid

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

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

- Cell membrane
This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.

2 related topics with Alpha

Overall
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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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.

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

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.