phospholipid

The phospholipids are amphiphilic. The hydrophilic end usually contains a negatively charged phosphate group, and the hydrophobic end usually consists of two "tails" that are long fatty acid residues.{{Citation |last1=Alberts |first1=Bruce |title=The Lipid Bilayer |date=2002 |url=https://www.ncbi.nlm.nih.gov/books/NBK26871/ |work=Molecular Biology of the Cell. 4th edition |access-date=2023-05-25 |publisher=Garland Science |language=en |last2=Johnson |first2=Alexander |last3=Lewis |first3=Julian |last4=Raff |first4=Martin |last5=Roberts |first5=Keith |last6=Walter |first6=Peter}}

In aqueous solutions, phospholipids are driven by hydrophobic interactions, which result in the fatty acid tails aggregating to minimize interactions with the water molecules. The result is often a phospholipid bilayer: a membrane that consists of two layers of oppositely oriented phospholipid molecules, with their heads exposed to the liquid on both sides, and with the tails directed into the membrane. That is the dominant structural motif of the membranes of all cells and of some other biological structures, such as vesicles or virus coatings.{{Cite journal |last=Lenard |first=John |last2=Compans |first2=Richard W. |date=1974-04-08 |title=The membrane structure of lipid-containing viruses |url=https://linkinghub.elsevier.com/retrieve/pii/0304415774900082 |journal=Biochimica et Biophysica Acta (BBA) - Reviews on Biomembranes |volume=344 |issue=1 |pages=51–94 |doi=10.1016/0304-4157(74)90008-2 |issn=0304-4157 |pmc=7148776 |pmid=4598854}}{{Cite journal |last=Posor |first=York |last2=Jang |first2=Wonyul |last3=Haucke |first3=Volker |date=Dec 2022 |title=Phosphoinositides as membrane organizers |url=https://www.nature.com/articles/s41580-022-00490-x |journal=Nature Reviews Molecular Cell Biology |language=en |volume=23 |issue=12 |pages=797–816 |doi=10.1038/s41580-022-00490-x |issn=1471-0080 |pmc=9117997 |pmid=35589852}}

File:Cell membrane detailed diagram 4.svg

In biological membranes, the phospholipids often occur with other molecules (e.g., proteins, glycolipids, sterols) in a bilayer such as a cell membrane.{{cite book | last = Campbell | first = Neil A. | author2 = Brad Williamson | author3 = Robin J. Heyden | title = Biology: Exploring Life | publisher = Pearson Prentice Hall | year = 2006 | location = Boston, Massachusetts | url = http://www.phschool.com/el_marketing.html | isbn = 978-0-13-250882-7 | access-date = 2008-12-14 | archive-date = 2014-11-02 | archive-url = https://web.archive.org/web/20141102041816/http://www.phschool.com/el_marketing.html }}{{page needed|date=October 2012}} Lipid bilayers occur when hydrophobic tails line up against one another, forming a membrane of hydrophilic heads on both sides facing the water.{{Citation |last=Alberts |first=Bruce |title=The Lipid Bilayer |date=2002 |work=Molecular Biology of the Cell. 4th edition |url=https://www.ncbi.nlm.nih.gov/books/NBK26871/ |access-date=2024-07-13 |publisher=Garland Science |language=en |last2=Johnson |first2=Alexander |last3=Lewis |first3=Julian |last4=Raff |first4=Martin |last5=Roberts |first5=Keith |last6=Walter |first6=Peter}}

These specific properties allow phospholipids to play an important role in the cell membrane. Their movement can be described by the fluid mosaic model, which describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane. Sterols contribute to membrane fluidity by hindering the packing together of phospholipids. However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.{{citation needed|date=December 2014}}

: See: Glycerophospholipid

• Phosphatidic acid (phosphatidate) (PA)
• Phosphatidylethanolamine (cephalin) (PE)
• Phosphatidylcholine (lecithin) (PC)
• Phosphatidylserine (PS)
• Phosphoinositides:
• Phosphatidylinositol (PI)
• Phosphatidylinositol 3-phosphate (PI3P)
• Phosphatidylinositol 4-phosphate (PI4P)
• Phosphatidylinositol 5-phosphate (PI5P)
• Phosphatidylinositol 4,5-bisphosphate (PIP2)
• Phosphatidylinositol (3,4,5)-trisphosphate (PIP3)

: See Sphingolipid

• Ceramide phosphorylcholine (Sphingomyelin) (SPH)
• Ceramide phosphorylethanolamine (Sphingomyelin) (Cer-PE)
• Ceramide phosphoryllipid

Phospholipids have been widely used to prepare liposomal, ethosomal and other nanoformulations of topical, oral and parenteral drugs for differing reasons like improved bio-availability, reduced toxicity and increased permeability across membranes. Liposomes{{Cite journal |last1=Akbarzadeh |first1=Abolfazl |last2=Rezaei-Sadabady |first2=Rogaie |last3=Davaran |first3=Soodabeh |last4=Joo |first4=Sang Woo |last5=Zarghami |first5=Nosratollah |last6=Hanifehpour |first6=Younes |last7=Samiei |first7=Mohammad |last8=Kouhi |first8=Mohammad |last9=Nejati-Koshki |first9=Kazem |date=2013-02-22 |title=Liposome: classification, preparation, and applications |journal=Nanoscale Research Letters |volume=8 |issue=1 |pages=102 |doi=10.1186/1556-276X-8-102 |doi-access=free |issn=1931-7573 |pmc=3599573 |pmid=23432972|bibcode=2013NRL.....8..102A }} are often composed of phosphatidylcholine-enriched phospholipids and may also contain mixed phospholipid chains with surfactant properties. The ethosomal formulation of ketoconazole using phospholipids is a promising option for transdermal delivery in fungal infections.[http://ethesis.nitrkl.ac.in/5377/1/411LS2068.pdf Ketoconazole Encapsulated Liposome and Ethosome: GUNJAN TIWARI]. Advances in phospholipid research lead to exploring these biomolecules and their conformations using lipidomics{{Cite journal |last1=Yang |first1=Kui |last2=Han |first2=Xianlin |date=November 2016 |title=Lipidomics: Techniques, applications, and outcomes related to biomedical sciences |journal=Trends in Biochemical Sciences |volume=41 |issue=11 |pages=954–969 |doi=10.1016/j.tibs.2016.08.010 |issn=0968-0004 |pmc=5085849 |pmid=27663237}}.{{citation needed|date=September 2022}}

Computational simulations of phospholipids are often performed using molecular dynamics with force fields such as GROMOS, CHARMM, or AMBER.{{Cite journal |last=Lyubartsev |first=Alexander P. |last2=Rabinovich |first2=Alexander L. |date=2016-10-01 |title=Force Field Development for Lipid Membrane Simulations |url=https://linkinghub.elsevier.com/retrieve/pii/S0005273615004393 |journal=Biochimica et Biophysica Acta (BBA) - Biomembranes |series=Biosimulations of lipid membranes coupled to experiments |volume=1858 |issue=10 |pages=2483–2497 |doi=10.1016/j.bbamem.2015.12.033 |issn=0005-2736}}

Phospholipids are optically highly birefringent, i.e. their refractive index is different along their axis as opposed to perpendicular to it. Measurement of birefringence can be achieved using cross polarisers in a microscope to obtain an image of e.g. vesicle walls or using techniques such as dual polarisation interferometry to quantify lipid order or disruption in supported bilayers.{{citation needed|date=September 2022}}

There are no simple methods available for analysis of phospholipids, since the close range of polarity between different phospholipid species makes detection difficult. Oil chemists often use spectroscopy to determine total phosphorus abundance and then calculate approximate mass of phospholipids based on molecular weight of expected fatty acid species. Modern lipid profiling employs more absolute methods of analysis, with NMR spectroscopy, particularly ³¹P-NMR,{{cite journal | url = http://www.jlr.org/content/29/5/679 | title = High resolution 31P NMR of extracted phospholipids |author1=N. Culeddu |author2=M. Bosco |author3=R. Toffanin |author4=P. Pollesello | year = 1998 | journal = Magnetic Resonance in Chemistry | volume = 36 | issue = 12 | pages = 907–912 | doi=10.1002/(sici)1097-458x(199812)36:12<907::aid-omr394>3.0.co;2-5| s2cid = 85602251 }}{{cite journal | doi = 10.1007/s12154-012-0090-1 | title = The lipidome and proteome of oil bodies from Helianthus annuus (common sunflower) | year = 2013 | last1 = Furse | first1 = Samuel | last2 = Liddell | first2 = Susan | last3 = Ortori | first3 = Catharine A. | last4 = Williams | first4 = Huw | last5 = Neylon | first5 = D. Cameron | last6 = Scott | first6 = David J. | last7 = Barrett | first7 = David A. | last8 = Gray | first8 = David A. | journal = Journal of Chemical Biology | volume = 6 | issue = 2 | pages = 63–76 | pmid = 23532185 | pmc = 3606697}} while HPLC-ELSD{{cite journal | title = HPLC analysis of phospholipids in crude oil for evaluation of soybean deterioration |author1=T. L. Mounts |author2=A. M. Nash | journal = Journal of the American Oil Chemists' Society | year = 1990 | volume =67 | issue =11 | pages = 757–760 | doi = 10.1007/BF02540486|s2cid=84380025 | url =https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=24329&content=PDF }} provides relative values.

{{See also|Biosynthesis#Phospholipids}}

Phospholipid synthesis occurs in the cytosolic side of ER membrane {{Cite journal |last1=Prinz |first1=William A. |last2=Choudhary |first2=Vineet |last3=Liu |first3=Li-Ka |last4=Lahiri |first4=Sujoy |last5=Kannan |first5=Muthukumar |date=2017-03-01 |title=Phosphatidylserine synthesis at membrane contact sites promotes its transport out of the ER |journal=Journal of Lipid Research |language=en |volume=58 |issue=3 |pages=553–562 |doi=10.1194/jlr.M072959 |doi-access=free |issn=0022-2275 |pmid=28119445 |pmc=5335585}} that is studded with proteins that act in synthesis (GPAT and LPAAT acyl transferases, phosphatase and choline phosphotransferase) and allocation (flippase and floppase). Eventually a vesicle will bud off from the ER containing phospholipids destined for the cytoplasmic cellular membrane on its exterior leaflet and phospholipids destined for the exoplasmic cellular membrane on its inner leaflet.{{cite book |title=Molecular Cell Biology |author=Lodish H. |author2=Berk A. |edition=6th |year=2007 |isbn=978-0-7167-7601-7 |publisher=W. H. Freeman |display-authors=etal}}{{cite journal |author=Zheng L. |author2=Lin Y. |author3=Lu S. |author4=Zhang J. |author5=Bogdanov M. | title = Biogenesis, transport and remodeling of lysophospholipids in Gram-negative bacteria | journal = Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids | volume = 1862 | issue = 11 | pages = 1404–1413 | date = November 2017 | pmid = 27956138 | pmc = 6162059 | doi = 10.1016/j.bbalip.2016.11.015 }}

Common sources of industrially produced phospholipids are soya, rapeseed, sunflower, chicken eggs, bovine milk, fish eggs etc. Phospholipids for gene delivery, such as distearoylphosphatidylcholine and dioleoyl-3-trimethylammonium propane, are produced synthetically.{{cn|date=July 2024}} Each source has a unique profile of individual phospholipid species, as well as fatty acids, and consequently differing applications in food, nutrition, pharmaceuticals, cosmetics, and drug delivery.{{citation needed|date=September 2022}}

Some types of phospholipid can be split to produce products that function as second messengers in signal transduction. Examples include phosphatidylinositol (4,5)-bisphosphate (PIP₂), that can be split by the enzyme phospholipase C into inositol triphosphate (IP₃) and diacylglycerol (DAG), which both carry out the functions of the G_q type of G protein in response to various stimuli and intervene in various processes from long term depression in neurons{{cite journal |doi=10.1523/JNEUROSCI.4084-05.2005 |title=Multiple Receptors Coupled to Phospholipase C Gate Long-Term Depression in Visual Cortex |year=2005 |last1=Choi |first1=S.-Y. |journal=Journal of Neuroscience |volume=25 |issue=49 |pages=11433–11443 |pmid=16339037 |pmc=6725895 |last2=Chang |first2=J. |last3=Jiang |first3=B. |last4=Seol |first4=G. H. |last5=Min |first5=S. S. |last6=Han |first6=J. S. |last7=Shin |first7=H. S. |last8=Gallagher |first8=M. |last9=Kirkwood |first9=A. }} to leukocyte signal pathways started by chemokine receptors.{{cite journal |doi=10.1189/jlb.0106035 |title=Evidence that phospholipase C-dependent, calcium-independent mechanisms are required for directional migration of T lymphocytes in response to the CCR4 ligands CCL17 and CCL22 |year=2006 |last1=Cronshaw |first1=D. G. |journal=Journal of Leukocyte Biology |volume=79 |issue=6 |pages=1369–1380 |pmid=16614259 |last2=Kouroumalis |first2=A. |last3=Parry |first3=R. |last4=Webb |first4=A. |last5=Brown |first5=Z. |last6=Ward |first6=S. G. |doi-access=free }}

Phospholipids also intervene in prostaglandin signal pathways as the raw material used by lipase enzymes to produce the prostaglandin precursors. In plants they serve as the raw material to produce jasmonic acid, a plant hormone similar in structure to prostaglandins that mediates defensive responses against pathogens.{{citation needed|date=October 2023}}

Phospholipids can act as emulsifiers, enabling oils to form a colloid with water. Phospholipids are one of the components of lecithin, which is found in egg yolks, as well as being extracted from soybeans, and is used as a food additive in many products and can be purchased as a dietary supplement. Lysolecithins are typically used for water–oil emulsions like margarine, due to their higher HLB ratio.{{citation needed|date=October 2023}}

: See table below for an extensive list.

• Natural phospholipid derivates:
• : egg PC (Egg lecithin), egg PG, soy PC, hydrogenated soy PC, sphingomyelin as natural phospholipids.
• Synthetic phospholipid derivates:
• Phosphatidic acid (DMPA, DPPA, DSPA)
• Phosphatidylcholine (DDPC, DLPC, DMPC, DPPC, DSPC, DOPC, POPC, DEPC)
• Phosphatidylglycerol (DMPG, DPPG, DSPG, POPG)
• Phosphatidylethanolamine (DMPE, DPPE, DSPE DOPE)
• Phosphatidylserine (DOPS)
• PEG phospholipid (mPEG-phospholipid, polyglycerin-phospholipid, functionalized-phospholipid, terminal activated-phospholipid)

• Cable theory
• Galactolipid
• Sulfolipid

{{Reflist}}

{{Membrane lipids}}

{{Phospholipids}}

{{Authority control}}

Category:Anionic surfactants