A report on Lipid bilayer

This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.
The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer.
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.

Thin polar membrane made of two layers of lipid molecules.

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

37 related topics with Alpha

Overall

Eukaryote

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Eukaryotes are organisms whose cells have a nucleus enclosed within a nuclear envelope.

Eukaryotes are organisms whose cells have a nucleus enclosed within a nuclear envelope.

The endomembrane system and its components
Simplified structure of a mitochondrion
Longitudinal section through the flagellum of Chlamydomonas reinhardtii
Structure of a typical animal cell
Structure of a typical plant cell
Fungal Hyphae cells: 1 – hyphal wall, 2 – septum, 3 – mitochondrion, 4 – vacuole, 5 – ergosterol crystal, 6 – ribosome, 7 – nucleus, 8 – endoplasmic reticulum, 9 – lipid body, 10 – plasma membrane, 11 – spitzenkörper, 12 – Golgi apparatus
This diagram illustrates the twofold cost of sex. If each individual were to contribute the same number of offspring (two), (a) the sexual population remains the same size each generation, where the (b) asexual population doubles in size each generation.
Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes
One hypothesis of eukaryotic relationships – the Opisthokonta group includes both animals (Metazoa) and fungi, plants (Plantae) are placed in Archaeplastida.
A pie chart of described eukaryote species (except for Excavata), together with a tree showing possible relationships between the groups
The three-domains tree and the Eocyte hypothesis
Phylogenetic tree showing a possible relationship between the eukaryotes and other forms of life; eukaryotes are colored red, archaea green and bacteria blue
Eocyte tree.
Diagram of the origin of life with the Eukaryotes appearing early, not derived from Prokaryotes, as proposed by Richard Egel in 2012. This view implies that the UCA was relatively large and complex.

They have two surrounding membranes, each a phospholipid bi-layer; the inner of which is folded into invaginations called cristae where aerobic respiration takes place.

Bacteria

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Bacteria (singular bacterium, common noun bacteria) are ubiquitous, mostly free-living organisms often consisting of one biological cell.

Bacteria (singular bacterium, common noun bacteria) are ubiquitous, mostly free-living organisms often consisting of one biological cell.

Rod-shaped Bacillus subtilis
Phylogenetic tree of Bacteria, Archaea and Eucarya. The vertical line at bottom represents the last universal common ancestor.
Bacteria display many cell morphologies and arrangements
The range of sizes shown by prokaryotes (Bacteria), relative to those of other organisms and biomolecules.
Structure and contents of a typical Gram-positive bacterial cell (seen by the fact that only one cell membrane is present).
An electron micrograph of Halothiobacillus neapolitanus cells with carboxysomes inside, with arrows highlighting visible carboxysomes. Scale bars indicate 100 nm.
Helicobacter pylori electron micrograph, showing multiple flagella on the cell surface
Bacillus anthracis (stained purple) growing in cerebrospinal fluid
Many bacteria reproduce through binary fission, which is compared to mitosis and meiosis in this image.
A culture of ''Salmonella
A colony of Escherichia coli
Helium ion microscopy image showing T4 phage infecting E. coli. Some of the attached phage have contracted tails indicating that they have injected their DNA into the host. The bacterial cells are ~ 0.5 µm wide.
Transmission electron micrograph of Desulfovibrio vulgaris showing a single flagellum at one end of the cell. Scale bar is 0.5 micrometers long.
The different arrangements of bacterial flagella: A-Monotrichous; B-Lophotrichous; C-Amphitrichous; D-Peritrichous
Streptococcus mutans visualised with a Gram stain.
Phylogenetic tree showing the diversity of bacteria, compared to other organisms. Here bacteria are represented by three main supergroups: the CPR ultramicrobacterias, Terrabacteria and Gracilicutes according to recent genomic analyzes (2019).
Overview of bacterial infections and main species involved.
Colour-enhanced scanning electron micrograph showing Salmonella typhimurium (red) invading cultured human cells
In bacterial vaginosis, beneficial bacteria in the vagina (top) are displaced by pathogens (bottom). Gram stain.
Antonie van Leeuwenhoek, the first microbiologist and the first person to observe bacteria using a microscope.

In contrast, Gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins.

Human cell nucleus

Nuclear envelope

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Human cell nucleus
A volumetric surface render (red) of the nuclear envelope of one HeLa cell. The cell was observed in 300 slices of electron microscopy, the nuclear envelope was automatically segmented and rendered. One vertical and one horizontal slice are added for reference.
Nuclear pores crossing the nuclear envelope
Breakdown and reassembly in mitosis.

The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes that in eukaryotic cells surrounds the nucleus, which encloses the genetic material.

The bacterium Escherichia coli (E. coli), is a single-celled prokaryote

Organism

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Organism is any organic, living system that functions as an individual entity.

Organism is any organic, living system that functions as an individual entity.

The bacterium Escherichia coli (E. coli), is a single-celled prokaryote
An amoeba is a single-celled eukaryote
Polypore fungi and angiosperm trees are large multicellular eukaryotes.
Precambrian stromatolites in the Siyeh Formation, Glacier National Park. In 2002, a paper in the scientific journal Nature suggested that these 3.5 Gya (billion years old) geological formations contain fossilized cyanobacteria microbes. This suggests they are evidence of one of the earliest known life forms on Earth.
LUCA may have used the Wood–Ljungdahl or reductive acetyl–CoA pathway to fix carbon.

A bilayer of phospholipids makes up the membrane of cells that constitutes a barrier, containing everything within a cell and preventing compounds from freely passing into, and out of, the cell.

Polarized membrane

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A polarized membrane is a lipid membrane that has a positive electrical charge on one side and a negative charge on another side, which produces the resting potential in living cells.

Archaea

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Archaea (singular archaeon ) constitute a domain of single-celled organisms.

Archaea (singular archaeon ) constitute a domain of single-celled organisms.

Archaea were found in volcanic hot springs. Pictured here is Grand Prismatic Spring of Yellowstone National Park.
The ARMAN are a group of archaea recently discovered in acid mine drainage.
Membrane structures. Top, an archaeal phospholipid: 1, isoprene chains; 2, ether linkages; 3, L-glycerol moiety; 4, phosphate group. Middle, a bacterial or eukaryotic phospholipid: 5, fatty acid chains; 6, ester linkages; 7, D-glycerol moiety; 8, phosphate group. Bottom: 9, lipid bilayer of bacteria and eukaryotes; 10, lipid monolayer of some archaea.
Bacteriorhodopsin from Halobacterium salinarum. The retinol cofactor and residues involved in proton transfer are shown as ball-and-stick models.
Sulfolobus infected with the DNA virus STSV1. Bar is 1 micrometer.
Archaea that grow in the hot water of the Morning Glory Hot Spring in Yellowstone National Park produce a bright colour
Methanogenic archaea form a symbiosis with termites.

The major structure in cell membranes is a double layer of these phospholipids, which is called a lipid bilayer.

Schematic diagram of an ion channel. 1 - channel domains (typically four per channel), 2 - outer vestibule, 3 - selectivity filter, 4 - diameter of selectivity filter, 5 - phosphorylation site, 6 - cell membrane.

Ion channel

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Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore.

Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore.

Schematic diagram of an ion channel. 1 - channel domains (typically four per channel), 2 - outer vestibule, 3 - selectivity filter, 4 - diameter of selectivity filter, 5 - phosphorylation site, 6 - cell membrane.
Selectivity filter allowing only potassium ions through the potassium channel (PDB: 1K4C).
Birth of an Idea (2007) by Julian Voss-Andreae. The sculpture was commissioned by Roderick MacKinnon based on the molecule's atomic coordinates that were determined by MacKinnon's group in 2001.

Such "multi-subunit" assemblies usually involve a circular arrangement of identical or homologous proteins closely packed around a water-filled pore through the plane of the membrane or lipid bilayer.

Lipid membrane bilayer

Biosynthesis

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Multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms.

Multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms.

Lipid membrane bilayer
Phosphatidic acid synthesis
Sphingosine synthesis
Cholesterol synthesis pathway
The synthesis of IMP.
Uridine monophosphate (UMP) biosynthesis
'Thymidylate synthase reaction: dUMP + 5,10-methylenetetrahydrofolate ⇔ dTMP + dihydrofolate
Ctp synthase mechanism: UTP + ATP + glutamine ⇔ CTP + ADP + glutamate
As DNA polymerase moves in a 3' to 5' direction along the template strand, it synthesizes a new strand in the 5' to 3' direction
L-amino acid
Glutamine oxoglutarate aminotransferase and glutamine synthetase
The diaminopimelic acid lysine biosynthetic pathway
The tRNA anticodon interacts with the mRNA codon in order to bind an amino acid to growing polypeptide chain.
The process of tRNA charging
Translation
Familial hypercholesterolemia causes cholesterol deposits

Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides.

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.

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

Bacterial outer membrane vesicles

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Bacterial outer membrane vesicles (OMVs) are vesicles of lipids released from the outer membranes of Gram-negative bacteria.