Chemistry
Conjugated Lipids
Conjugated lipids are a type of lipid molecule that contains multiple double bonds in their hydrocarbon chains. These double bonds are separated by single bonds, creating a conjugated system. This arrangement gives conjugated lipids unique chemical and physical properties, making them important in various biological processes and as potential targets for drug development.
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eBook - PDFAdvanced Chemical Biology
Chemical Dissection and Reprogramming of Biological Systems
- Howard C. Hang, Matthew R. Pratt, Jennifer A. Prescher, Howard C. Hang, Matthew R. Pratt, Jennifer A. Prescher(Authors)
- 2023(Publication Date)
- Wiley-VCH(Publisher)
243 11 Chemical Biology of Lipids Scotland Farley, Alix Thomas, Aurélien Laguerre, and Carsten Schultz Oregon Health and Science University, Department of Chemical Physiology and Biochemistry, 3181 SW Sam Jackson Park Road, L334, Portland, OR 97239, USA 11.1 Introduction Of the four classes of biomolecule that make up every cell – proteins, nucleic acids, carbohydrates, and lipids – lipids, for most of the time we have known about them, have been relegated to an inert, structural role. Slowly, it became understood that the “lipid bilayer” is far from a uniform or constant structure, characterized by tens of thousands of individual lipid species, myriad different conformations within and around the cell, and multiple complex biophysical phases, all of which interface with each other and the biomolecules around them to facilitate cellular processes. Even more recently, another layer of lipid function has emerged, as we have come to understand that lipids, in addition to their crit- ical structural functions, also have important signaling roles both intracellularly and extracellularly [1–4]. For instance, the highly phosphorylated lipid phosphatidyli- nositol 4,5-bisphosphate (PIP 2 ) is a crucial cofactor of many ion channels and other transmembrane proteins [5]. Add another phosphate and you have the signaling lipid phosphatidylinositol 3,4,5-trisphosphate (PIP 3 ), a rare and transiently formed species that transmits growth factor receptor signals by recruiting kinases to the plasma membrane [6]. Extracellularly abundant lipids such as lysophosphatidic acid (LPA) activate G-protein-coupled receptors on cell surfaces to induce diverse effects such as cytoskeleton reorganization, cell migration, proliferation, survival, and cell–cell com- munication [7]. Lipids are involved in many diseases including atherosclerosis and genetically transmitted lipid storage diseases such as Niemann–Pick C (NPC) with often dramatic outcomes for the patients.
eBook - PDF- Jose Perez-Castineira(Author)
- 2020(Publication Date)
- De Gruyter(Publisher)
4 Lipids 4.1 Definition and classification Lipids are a heterogeneous family of biomolecules whose common characteristic is a low or null solubility in water and high solubility in non-polar organic solvents such as chloroform or hexane. This definition includes a wide variety of biological com- pounds that can be classified according to different criteria, such as behavior upon hydrolyzation or chemical structure and composition [1]. According to the first crite- rion, lipids are classified as: – Hydrolysable (saponifiable) lipids. Those that yield fatty acids when subjected to hydrolysis in the presence of strong acids (soaps in the presence of strong bases such as NaOH or KOH). – Non-hydrolysable (unsaponifiable) lipids. They do not produce fatty acids/soaps upon hydrolysis. Considering chemical structure and composition, food chemists distinguish three clas- ses of lipids: – Simple lipids: esters of fatty acids and biological alcohols like glycerol (propane- 1,2,3-triol). This group is of paramount importance due to their abundance in foods, as they include fats and oils. – Compound, complex, or Conjugated Lipids: lipids linked or associated to other non-lipid molecules producing substances with amphiphilic properties. These include phospholipids, glycolipids, and lipoproteins. – Derived lipids. Hydrophobic substances not included in the above groups, such as free fatty acids, carotenoids, lipophilic vitamins, steroids, or pigments and volatile scents from plants. Similarly to the rest of biomolecules, the backbones of lipids are composed mainly of carbon, hydrogen, and oxygen although they may contain additional elements such as phosphorus, sulfur, and/or nitrogen. Lipids are molecules of hydrophobic nature implicated in important biological functions: – Energetic.
eBook - PDFOrganic Chemistry
A Mechanistic Approach
- Penny Chaloner(Author)
- 2014(Publication Date)
- CRC Press(Publisher)
719 16.1 INTRODUCTION This chapter deals with two classes of natural products, lipids and carbohydrates; the chemis- try involved is applied carbonyl and alcohol chemistry. Although the molecules we will meet are often larger and appear more complex than those we discussed in previous chapters, what happens to them is essentially the same as with the simpler molecules. We will meet some new reagents, especially in carbohydrate chemistry, but the need for these mostly reflects a difference in the solubility of the substrates. Most organic molecules are soluble in organic solvents, but carbohydrates have limited solubility in organic solvents and are very soluble in water. However, the processes they undergo have not changed. 16.2 LIPIDS The term lipid technically means fat, but it is used to describe quite a wide range of related compounds, including fatty acids, steroids, prostaglandins, lipoproteins, sphingolipids, and phos- pholipids. Fatty acids and triglycerides are energy sources and used for energy storage as well as cell membrane construction. Steroids and prostaglandins fulfill many biological functions as chemical messengers. Some of these molecules, particularly the fatty acids, have a single polar “head group” and a long hydrocarbon “tail.” Despite the head group, they are generally more soluble in nonpolar than in polar media and have surfactant properties, explored in more detail in Section 16.2.1. They are sometimes called amphiphiles, as there is one part of the molecule, the head group, that is best solubilized in water and one part, the hydrocarbon tail, that is more com- patible with nonpolar solvents (Figure 16.1). This allows the formation of a range of structures including monolayers, bilayers, micelles, and vesicles, depending on the molecule, the solvent, and the concentration. 16.2.1 SURFACTANTS Figure 16.1 shows a typical surfactant molecule, with a polar head group and a nonpolar tail.
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