Derived Lipids
Derived lipids are a diverse group of compounds formed from the chemical modification of simple lipids. They include phospholipids, glycolipids, and cholesterol, which play essential roles in cell structure, signaling, and energy storage. These lipids are characterized by their varied structures and functions, contributing to the complexity and versatility of biological systems.
6 Key excerpts on "Derived Lipids"
eBook - ePub- Jose Perez-Castineira(Author)
- 2020(Publication Date)
- De Gruyter(Publisher)
...In 2005, an updated definition as well as a comprehensive classification of these molecules was introduced based on their biochemical properties. Lipids were defined as “hydrophobic or amphipathic small molecules that may originate entirely or in part by carbanion-based condensations of thioesters and/or by carbocation-based condensation of isoprene units” [ 7 ]. Additionally, the term simple lipids was proposed for those that yield up to two types of products upon hydrolysis (e.g. fatty acids, sterols, and acylglycerols), and complex lipids for those yielding three or more products (e.g. glycerophoshopilids and glycosphingolipids). Naturally occurring lipids were classified into eight categories that cover eukaryotic and prokaryotic sources (Table 4.1, Figure 4.1), each category being subdivided into classes and subclasses. The LIPID MAPS initiative also proposed an appropriate nomenclature as well as guidelines for drawing the structures of these biomolecules [ 7, 8 ]. Another commonly accepted definition describes simple lipids as those that do not have fatty acids in their molecules (terpenes, hydrocarbons, steroids, and prostaglandins) and complex lipids as those that contain fatty acids (acylglycerides, phospholipids, glycolipids, sphingolipids, and waxes). Figure 4.1: Chemical structures of the lipid compounds mentioned in Table 4.1...
eBook - ePub- S. P. Bhutani(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...Lipids also include molecules such as fatty acids and their derivatives, cholesterol and all other compounds obtained from cholesterol. Terpenoids and carotenoids also come under lipids. Lipids are hydrophobic in nature. They originate entirely or in part from two distinct types of biochemical subunits or “building blocks”–ketoacyl and isoprene groups. We consume oils and fats in our daily diet. Dietary fats supply energy, carry fat-soluble vitamins- A, D, E, K and are a source of antioxidants and bioactive compounds. Fats are also incorporated as structural components of the brain and cell membranes. 5.2 CLASSIFICATION OF LIPIDS—TYPES OF LIPIDS Lipids may be classified into four major groups: 1. Simple Lipids i. Fats and oils ii. Waxes 2. Complex Lipids i. Phospholipids ii. Glycolipids iii. Sphingolipids 3. Derived Lipids i. Sterol lipids — Steroids and sterols ii. Prenol lipids — Isoprenoids or Terpenes 4. Unclassified Lipids Tocopherols (vitamin E) and vitamin K A. Simple Lipids The simple lipids are esters of monocarboxylic fatty acids and aliphatic alcohols. Simple lipids are of the following types: i. Fats and Oils Fats and oils are triglycerides formed of glycerol and fatty acids. Glycerol contains three hydroxyl groups. When all the three alcoholic groups form ester linkages with fatty acids, the resulting compound is a triacylglycerol (1). The older name of this type of compound is triglyceride. The three ester groups are the polar parts of the molecule, whereas the tails of the fatty acids are non-polar. Three different fatty acids are usually esterified to the alcoholic groups of the glycerol molecule. Triacylglycerols do not occur as components of the membranes as do other types of lipids. They accumulate in adipose tissue and provide a means of storing fatty acids particularly in animals. They serve as concentrated stores of metabolic energy...
eBook - ePub- Guoyao Wu(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...3 Chemistry of Lipids Lipids are defined as hydrocarbon compounds that are soluble in organic solvents (e.g., chloroform and ethanol) and, except for some small molecules, are generally insoluble in water (Gunstone 2012). These substances are highly reduced molecules, with the highest proportions of hydrogen atoms among all dietary macronutrients. Since lipids are classified solely on the basis of their hydrophobic properties, they have diverse chemical structures and biological functions. In nature, examples of lipids are fatty acids, triacylglycerols (TAGs), glycerolipids, glycerophospholipids, sphingolipids, cholesterol, cortisol, testosterone, progesterone, and vitamin A (Mead et al. 1986). Lipids account for 1%–50% of the body weights of animals, depending on their species, age, nutritional state, and disease (Cherian 2015; Pond et al. 2005). Plants and algae are excellent sources of fatty acids that are not synthesized by animals (NRC 2011, 2012). In proximate feedstuff analysis, lipids are determined together as the ether extract and are called crude fats. Lipids are important structural and cellular components in plants, animals, and microorganisms. These substances are widely distributed in the cell membrane and the membranes of intracellular organelles to control the transport of gases, nutrients, ions, and metabolites into and out of cells (Ridgway and McLeod 2016). In animals, TAGs are the major form of energy storage, and fatty acids are the primary metabolic fuels for such key organs as the liver, skeletal muscle, and heart, while facilitating the digestion and absorption of fat-soluble vitamins (Conde-Aguilera et al. 2013; Smith and Smith 1995). In neonates, subcutaneous white adipose tissue insulates the body from the loss of heat. In many mammals, brown adipose tissue oxidizes fatty acids to produce large amounts of heat, thereby keeping the body warm during the neonatal period (Smith and Carstens 2005; Satterfield and Wu 2011)...
eBook - ePub- Antonio Blanco, Gustavo Blanco(Authors)
- 2017(Publication Date)
- Academic Press(Publisher)
...Some have a linear molecule (geraniol, farnesol, squalene, and polyprenols) others present cyclic structures (vitamin A, carotenes, lanosterol, and ubiquinone) and sterols (derivative from cyclopentanoperhydrophenanthrene). Cholesterol is a sterol precursor for the synthesis of sexual and adrenocortical hormones, bile acids, and vitamin D. They are generically called steroids. Keywords fatty acids saturated monosaturated polyunsaturated soap acylglycerol glycerophospholipid phosphatidic acid phospholipid sphingophospholipids cerebroside gangliosides sulfolipid glycolipids lipoproteins terpenes isoprene geraniol farnesol squalene sterols cholesterol Lipids, widely distributed in animals and plants, comprise a heterogeneous group of substances which share the common characteristic of having little or no solubility in water, but good solubility in nonpolar substances (a substance is soluble in solvents of similar nature; polar substances dissolve in polar solvents, nonpolar substances in nonpolar solvents). Different from polypeptides or polysaccharides, lipids do not form macromolecular polymers and do not have high molecular mass. The study of lipids is important because (1) lipids are essential components of living beings, constituting a fundamental part of cell membranes; (2) they are the main energy reserve (neutral fats) in animals; (3) they are of essential nutritional value because lipids have a high-caloric content, they transport fat-soluble vitamins, and supply indispensable compounds [essential fatty acids (FAs)] that humans cannot synthesize; and (4) they comprise a number of substances of critical physiological activity, including hormones, certain vitamins, and bile acids. Classification According to the complexity of the molecule, lipids can be classified into two different types: simple and complex. In addition, there are other substances associated with lipids that share their solubility properties...
eBook - ePub- Raymond S. Ochs(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...3 Lipids A defining characteristic of lipids is their relative insolubility in water. Chemically, lipids are relatively simple – consisting mostly of unreactive hydrocarbons – making this topic an appropriate next step in our study. Lipids play a role in virtually every aspect of cellular biology and disease states of the body. The myriad of forms that serve this purpose arises from relatively modest variations in structure. Here, we consider the major types of lipid molecules and their principal roles. 3.1 Significance The primary functions of lipids are energy storage and membrane formation. Beyond this, lipids can form micelles in the digestive process, monolayers in the lung lining and lipid droplets, and serve as signal molecules. Distinct structures correspond to each function. For the storage role, the predominant chemical species is the triacylglycerol, also known as triglycerides. These molecules are virtually insoluble in water and are classified as nonpolar lipids. For the membrane function, the most prominent molecules are the phospholipids, which are partially water soluble. Membrane lipids are classified as polar lipids. We begin our structural examination by considering a building block of both triacylglycerols and phospholipids, the fatty acids. 3.2 Fatty Acids Fatty acids are molecules with two parts: a long hydrocarbon segment, called a “tail”, and a smaller region that typically consists of a carboxyl group, called the “head” (Figure 3.1). FIGURE 3.1 Parts of a fatty acid. The hydrophobic portion is the tail; the hydrophilic is the head. Usually, numbering systems consider the carboxyl group as carbon 1. The hydrocarbon tail consists mostly of chemically unreactive methylene groups and a variable number of double bonds. Table 3.1 presents the structures and nomenclature of some naturally occurring fatty acids...
- Dennis E. Vance, J.E. Vance(Authors)
- 1996(Publication Date)
- Elsevier Science(Publisher)
...Chapter 1 Physical properties and functional roles of lipids in membranes Pieter R. Cullis 1, 2 ; David B. Fenske 1 ; Michael J. Hope 2, 3 1 Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, B.C., V6T1Z3, Canada, 2 Inex Pharmaceuticals Corp., 1779 W. 75th Avenue, Vancouver, B.C., V6P 6P2, Canada 3 Division of Dermatology, Faculty of Medicine, University of British Columbia, Vancouver, B.C., V5Z1L7, Canada 1 Introduction and overview Biological membranes contain an astonishing variety of lipids. As detailed throughout this book, generation of this diversity requires elaborate metabolic pathways. The lipid compounds representing the end products of these pathways must bestow significant evolutionary advantages to the cellular or multicellular systems in which they reside, implying particular functional roles for each component. However, clarification of the functional roles of individual lipid species has proven a difficult problem. Here we present a synopsis of the physical properties of lipid systems and indicate how they may relate to the functional capacities of biological membranes. The major role of membrane lipids has been understood in broad outline since the early experiments of Gorter and Grendell [1], who extracted lipids from the erythrocyte membrane and measured the areas these lipids were able to cover as a monolayer at an air–water interface. This work led to the conclusion that the erythrocytes contained sufficient lipid to provide a bilayer lipid matrix surrounding the red blood cell. This bilayer lipid organization, which provides a permeability barrier between exterior and interior compartments, has remained a dominant theme in our understanding of the organization and function of biological membranes...
