Phospholipids

from Wikipedia, the free encyclopedia
Schematic representation of phospholipids, for example as part of a membrane. 1. Hydrophilic head. 2. Hydrophobic tail.
Different structures that phospholipids can adopt in aqueous solutions: liposome , micelle , and double lipid layer (main component of the biomembrane )

Phospholipids are a group of lipids with a phosphate group . Phospholipids belong to the polar lipids .

properties

Phospholipids are made up of a hydrophilic (water-loving) head and two hydrophobic (water-repellent) hydrocarbons . You are amphiphilic . They are involved in the structure of the lipid bilayer of many biomembranes and are therefore found in all animal and plant cells. Phospholipids are naturally occurring surfactants . Phospholipids are also intracellular signaling molecules, as well as components of the bile and surfactant .

The biosynthesis of phospholipids is closely related to the biosynthesis of the cell membrane . It takes place in all cells and takes place in the endoplasmic reticulum (ER) and Golgi apparatus .

Subgroups

Due to their chemical structure, phospholipids are divided into two groups:

There are also so-called plasmalogens . These differ from phosphoglycerides only in that, instead of a fatty acid, they carry an unsaturated alcohol linked via an ether bridge (e.g. –O – CH = CH– (CH 2 ) n –CH 3 ) on the C 1 atom of the glycerol . They make up 50% of the heart's phospholipids . At 10%, they are the most common molecules in the central nervous system , but they also occur in the heart and skeletal muscles . Their function has not yet been finally clarified.

Biomembranes

Besides glycolipids and cholesterol, phospholipids are one of the three main groups of membrane lipids. The phospholipids are responsible for the typical membrane structure. They owe this property to their amphiphilia. In an aqueous environment like in the human body, the following happens: Their polar head groups turn towards the water and their non-polar hydrocarbon tails repel water and accumulate inward. The drive for the assembly of the hydrocarbon tails is called the hydrophobic interaction.

Micelles

One possibility for the formation of a globular structure by phospholipids in an aqueous medium is the formation of micelles. The outside is formed here by the polar heads and the inside by the interacting hydrocarbon tails.

Double lipid layer

Another possibility of membrane formation by phospholipids can be found in almost all biological membranes. For example the cell membrane (plasma membrane). A closed lipid bilayer limits the cell to the outside and its cell compartments inside. These membranes are essential to life. The ability to form a membrane lies in the structure of the phospholipids. Hydrophobic interactions between the fatty acid chains can be grouped together. The non-polar hydrocarbon tails repel the water and create a barrier which, as a closed structure, forms a membrane between an interior and an exterior space.

The most common phospholipids found in a cell membrane are:

Liposome

Another possibility of membrane formation by phospholipids is the formation of liposomes (also lipid vesicles ), which, in contrast to a micelle, are surrounded by a lipid bilayer. Liposomes can be used as a model for membrane permeability studies or as a delivery vehicle for drugs.

Dismantling

Phospholipids are enzymatically broken down in the body by phospholipases. With the addition of water, bonds are broken. Phospholipases belong to the hydrolase enzyme group. They are divided, among other things, according to the location of their attack on a phospholipid.

research

There is a high probability that phospholipids can be used as biomarkers for cancer in the future. This is the subject of current research (2016).

See also

Individual evidence

  1. ^ Hans Beyer, Wolfgang Walter, Wittko Francke: Textbook of organic chemistry . 23rd edition. S. Hirzel Verlag, Stuttgart, Leipzig 1998, ISBN 3-7776-0808-4 , p. 326 .
  2. ↑ a b Florian Horn: Biochemistry of humans. The textbook for medical studies . 5th edition. Georg Thieme Verlag, Stuttgart, New York 2012, ISBN 978-3-13-130885-6 , pp. 161 ( limited preview in Google Book search).
  3. ↑ a b c Florian Horn: Biochemistry of humans. The textbook for medical studies . 5th edition. Georg Thieme Verlag, Stuttgart, New York 2012, ISBN 978-3-13-130885-6 , pp. 162 ( limited preview in Google Book search).
  4. ↑ Entry on phospholipids. In: Römpp Online . Georg Thieme Verlag, accessed on December 9, 2014.
  5. ↑ a b c d e Jeremy M. Berg, Lubert Stryer, John L. Tymoczko: Stryer Biochemie . Springer Spectrum, 2012, ISBN 978-3-8274-2988-9 , pp. 348-358 .
  6. ^ A b c Axel Zeeck, Stephanie Grond, Ina Papastavrou, Sabine C. Zeeck: Chemistry for medical professionals . Ed .: Axel Zeeck. 7th edition. Elsevier, Munich 2010, ISBN 978-3-437-42443-4 .
  7. ↑ Raju Bandu, Hyuck June Mok, Kwang Pyo Kim: phospholipid as cancer biomarkers: Mass spectrometry-based analysis . In: Mass Spectrometry Reviews . 2016. doi : 10.1002 / mas.21510 .