Biological Sciences
Lipids
Lipids are a diverse group of organic molecules that are insoluble in water. They serve as energy storage, structural components of cell membranes, and signaling molecules. Common types of lipids include fats, phospholipids, and steroids. They play crucial roles in maintaining cell structure and function, as well as serving as a source of energy for the body.
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eBook - PDF- Jose Perez-Castineira(Author)
- 2020(Publication Date)
- De Gruyter(Publisher)
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. The most energy-dense biomolecules are Lipids, containing up to 9 kilocalories (kcal, approximately 37.6 kilojoules or kJ) per gram; therefore, they are the molecules of choice for efficient energy storage in vertebrates and other species [1]. – Structural. PhosphoLipids, glycoLipids, and sterols play an essential role in the structure and function of biological membranes, the complex structure that me- diates the interchange of mass, energy, and information between the cell and its environment [2]. https://doi.org/10.1515/9783110595482-004 – Insulation and protection. Some Lipids are important components of animal skin and feathers as well as plant cuticles [3]. – Cell signaling and regulation. Many intra- and extracellular chemical messen- gers are Lipids [4]. – Antioxidants. Vitamin E is the most important lipophilic protectant against oxida- tive damage of biological membranes. Some carotenoids have also been reported to be antioxidants (Chapter 8). – Electron carriers, like coenzyme Q10 in the mitochondrial respiratory chains. – Enzymatic co-factors. Some hydrophobic molecules, like vitamin K, are required by some enzymes to exert their biological functions [5]. The importance of the different roles played by Lipids in vivo led biochemists to launch the LIPID MAPS (“LIPID Metabolites and Pathways Strategies”) initiative in 2002 that set off the development of lipidomics. Lipidomics aims at the identification, characterization, and quantification of the lipidome, that is, the entire spectrum of Lipids and derived metabolites in a biological system [4, 6].
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.
- Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
The hydrophobic nature of Lipids contributes significantly to the biological functions of these molecules. Their water insolubility allows Lipids to serve as barriers to aqueous solu- tions. This property, as we shall see later, is of great importance when Lipids form cellular membranes. Lipids are hydrophobic molecules; their structures are relatively large and nonpolar. Yet, within this broad description, lipid structures vary markedly. The following classification scheme recognizes important structural differences: 1. Simple Lipids (a) Fats and oils: esters of fatty acids and glycerol. (b) Waxes: esters of high-molar-mass fatty acids and high-molar-mass alcohols. 2. Compound Lipids (a) PhosphoLipids: substances that yield glycerol, phosphoric acid, fatty acids, and a nitrogen-containing base upon hydrolysis. (b) SphingoLipids: substances that yield an unsaturated amino alcohol (sphingosine), a long-chain fatty acid, and either a carbohydrate or phosphate and a nitrogen base upon hydrolysis. (c) GlycoLipids: substances that yield sphingosine, a fatty acid, and a carbohydrate upon hydrolysis. 3. Steroids Substances that possess the steroid nucleus, which is a 17-carbon structure consisting of four fused carbocyclic rings. Cholesterol and several hormones are in this class. 4. Miscellaneous Lipids Substances that do not fit into the preceding classifications; these include the fat-soluble vitamins A, D, E, and K, and lipoproteins. KEY TERM Lipids An ester is formed by splitting out a molecule of water between an alcohol and an acid. LEARNING OBJECTIVE 28.2 • Simple Lipids 733 The most abundant Lipids are the fats and oils. These substances constitute one of the three important classes of foods. In the discussion that follows, we examine fats and oils as they pertain to biochemistry. A more complete consideration of the properties and composition of various fats and oils is given in Section 24.9.
eBook - PDF- Papita H Gourkhede(Author)
- 2023(Publication Date)
- Arcler Press(Publisher)
BIOCHEMISTRY OF Lipids CHAPTER8 CONTENTS 8.1. Introduction .................................................................................... 214 8.2. Diversity in Lipid Structure ............................................................. 217 8.3. Properties of Lipids In Solution ....................................................... 219 8.4. Engineering of Membrane Lipid Composition ................................. 223 8.5. Role of Lipids in Cell Function ........................................................ 227 8.6. Lipid Metabolism in Plants.............................................................. 237 8.7. Plant Lipid Geography .................................................................... 238 8.8. Future Directions of Lipids .............................................................. 239 8.9. Conclusion ..................................................................................... 241 References ............................................................................................. 242 Biochemistry and its Application 214 Including fats, oils, hormones, and certain components of membranes that are grouped together, Lipids, are a diverse group of organic compounds because they do not interact appreciably with water. As fat in adipose cells, one type of lipid, the triglycerides provides thermal insulation and serves as the energy-storage depot for organisms. Between cells, tissues, and organs, some Lipids such as steroid hormones serve as chemical messengers and others between biochemical systems within a single cell communicate signals. The membranes of cells and organelles (structures within cells) are microscopically thin structures formed from two layers of phospholipid molecules. 8.1. INTRODUCTION To separate individual cells from their environments and to compartmentalize the cell interior into structures, membranes function to carry out special functions.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter-2 Lipids and Nucleotide Lipids Structures of some common Lipids. At the top are oleic acid and cholesterol. The middle structure is a triglyceride composed of oleoyl, stearoyl, and palmitoyl chains attached to a glycerol backbone. At the bottom is the common phospholipid, phosphatidylcholine. Lipids are a broad group of naturally occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phosphoLipids, and others. The main biological functions of Lipids include energy storage, as structural components of cell membranes, and as important signaling molecules. Lipids may be broadly defined as hydrophobic or amphiphilic small molecules; the amphiphilic nature of some Lipids allows them to form structures such as vesicles, liposomes, or membranes in an aqueous environment. Biological Lipids originate entirely or in part from two distinct types of biochemical subunits or building blocks: ketoacyl ____________________ WORLD TECHNOLOGIES ____________________ and isoprene groups. Using this approach, Lipids may be divided into eight categories: fatty acyls, glyceroLipids, glycerophosphoLipids, sphingoLipids, saccharoLipids and polyketides (derived from condensation of ketoacyl subunits); and sterol Lipids and prenol Lipids (derived from condensation of isoprene subunits). Although the term lipid is sometimes used as a synonym for fats, fats are a subgroup of Lipids called triglycerides. Lipids also encompass molecules such as fatty acids and their derivatives (including tri-, di-, and monoglycerides and phosphoLipids), as well as other sterol-containing metabolites such as cholesterol. Although humans and other mammals use various biosynthetic pathways to both break down and synthesize Lipids, some essential Lipids cannot be made this way and must be obtained from the diet.
eBook - PDF- A.G. Lee(Author)
- 1995(Publication Date)
- Elsevier Science(Publisher)
THE FUNCTIONAL ROLES OF Lipids IN BIOLOGICAL MEMBRANES David B. Fenske, Myrna A. Monck, Michael J. Hope, and Pieter R. Cullis I. II. III. IV. V. VI. VII. VIII. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Lipid Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Lipid Physical Properties and Phase Transitions .................. 4 Lipid Polymorphism ................................ 6 Lipids and Membrane Fusion .......................... 11 Orientational Order in Lipid Bilayers ...................... 13 Permeability and the Osmotic Properties of Membranes ............ 18 The Role of Lipids in Protein Function ..................... 20 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Acknowledgments ................................ 22 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Biomembranes Volume 1, pages 1-28. Copyright 9 1995 by JAI Press Inc. All rights of reproduction in any form reserved. ISBN: 1-55938-658-4 2 D.B. FENSKE, M. A. MONCK, M. J. HOPE, and P. R. CULLIS I. INTRODUCTION Biological membranes surround cells and organelles, divide the interior of eu- karyotic cells into distinct compartments, and provide surfaces for the localization of metabolic enzymes, transport proteins, receptors, and various substrates. In addition, membranes are semipermeable barriers which regulate the transport of water, ions, and other metabolites, thereby providing a means of controlling the internal environment. Our basic understanding of membrane structure has changed little since Singer and Nicholson (1972) first proposed the fluid-mosaic model over 20 years ago. Biological membranes are fluid (liquid-crystalline) lipid bilayers, into which proteins can insert or associate at the surface.
eBook - PDFAdvanced Nutrition
Macronutrients, Micronutrients, and Metabolism, Second Edition
- Carolyn D. Berdanier, Lynnette A. Berdanier(Authors)
- 2015(Publication Date)
- CRC Press(Publisher)
261 10 Lipids The third macronutrient group consists of Lipids. They are energetically more dense than carbo-hydrates having more than twice the energy value of carbohydrate per gram. Americans consume approximately 32%–42% of their total energy intake as lipid. Lipids make up a group of compounds that are, in general, insoluble in water and soluble in nonaqueous solvents. They are present in varying amounts in all living cells. Nerve cells and adipose cells are rich in lipid; muscle cells and epithelial cells have less. In addition to being a very important source of energy, Lipids serve a variety of other needs. They perform a basic role in the structure and function of biological membranes. In the body, they are the precursors of a variety of hormones and also act as some important cell signals. CLASSIFICATION Lipids are relatively soluble in such solvents as ether, chloroform, benzene, and some alcohols. Additionally, some Lipids are saponifiable; others are not. Saponifiable Lipids, when treated with alkali, undergo hydrolysis at the ester linkage, resulting in the formation of an alcohol and a soap (fatty acids combined with hydroxide). Triacylglycerol (TG) (triglyceride), for example, when treated with sodium hydroxide, is hydrolyzed yielding a mixture of soaps and free glyc-erol. Traditionally, saponifiable Lipids have been classified into three groups (A, B, C), each with subgroups. A. Simple Lipids: esters of fatty acids with various alcohols 1. Fats: esters of fatty acids with glycerol (acylglycerols) 2. Waxes: esters of fatty acids with long chain alcohols 3. Cholesterol esters B. Compound Lipids: esters of fatty acids that contain substituent groups in addition to fatty acids and alcohol 1. PhosphoLipids: esters of fatty acids, alcohol, a phosphoric acid residue, and usually an amino alcohol, sugar, or other substituent 2. GlycoLipids: esters of fatty acids that contain carbohydrates and nitrogen (but not phos-phoric acid).
eBook - PDFChemistry for Today
General, Organic, and Biochemistry
- Spencer Seager, Michael Slabaugh, Maren Hansen, , Spencer Seager, Spencer Seager, Michael Slabaugh, Maren Hansen(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
(Section 18.3) 5 Write key reactions for fats and oils. (Section 18.4) 6 Compare the structures of fats and waxes. (Section 18.5) 7 Draw structural formulas and describe uses for phospho- glycerides. (Section 18.6) 8 Draw structural formulas and describe uses for sphingoLipids. (Section 18.7) 9 Describe the major features of cell membrane structure. (Section 18.8) 10 Identify the structural characteristic typical of steroids and list important groups of steroids in the body. (Section 18.9) 11 Name the major categories of steroid hormones. (Section 18.10) 12 Describe the biological importance and therapeutic uses of the prostaglandins. (Section 18.11) iStock.com/kali9 Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Lipids 583 T HE GROUP OF COMPOUNDS called Lipids is made up of substances with widely different compositions and structures. Unlike carbohydrates, which are defined in terms of structure, Lipids are defined in terms of a physical property—solubility. Lipids are biological molecules that are insoluble in water but soluble in nonpolar solvents. Lipids are the waxy, greasy, or oily compounds found in plants and animals (see Figures 18.1 and 18.2). Lipids repel water, a useful characteristic of protective wax coatings found on some plants. Fats and oils are energy-rich and have relatively low densities. These properties account for their use as storage forms of energy in plants and animals. Still other Lipids are used as structural components, especially in the for- mation of cellular membranes. FIGURE 18.1 Waxes form a protective coating on these leaves.
eBook - PDF- Ronald Aloia(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Chapter Structural Properties of Lipids and Their Functional Roles in Biological Membranes 1 P. R. Cullis 2 , B. de Kruijff, M. /. Hope, A. /. Verkleij, R. Nayar, S. B. Farren, C Tilcock 3 , T. D. Madden 3 , and M. B. Bally Introduction 40 Structural Preferences of Membrane Lipids 43 Introduction 43 Techniques for Visualizing Lipid Organization 44 Phase Preferences of Lipids 45 Isothermal Modulation of Membrane Lipid Structure 52 Influence of Divalent Cations and pH 52 Influence of Protein on Membrane Lipid Structure 58 Potential Roles of Nonbilayer Lipid Structures in Membranes 60 Membrane Fusion 60 Exocytosis 65 Transbilayer Transport 66 Intermembrane Communication 70 A Rationale for Lipid Diversity—The Shape Concept 71 Closing Remarks 77 References 79 J The research presented here was supported by the MRC (Canada), the Canadian Heart Foundation (B.C. chapter), and the B.C. Health Care Research Foundation. 2 Scholar of the MRC (Canada). 3 MRC (Canada) Postdoctoral Fellow. Membrane Fluidity in Biology, Vol. 1 39 Copyright © 1983 by Academic Press, Inc. Concepts of Membrane Structure All rights of reproduction in any form reserved. ISBN 0-12-053001-5 40 P.R.Cullis et al. Introduction It is commonly assumed that Lipids in biological membranes play rather inert structural roles, serving to maintain a permeability barrier between external and internal environments as well as providing a matrix with which func-tional membrane proteins are associated. However the sheer diversity of membrane Lipids, as indicated in Fig. 1 for phosphoLipids, suggests that this does not provide a complete picture. A single phospholipid species such as phosphatidylcholine could maintain the required liquid crystalline bilayer envelope, immediately leading to questions concerning the functional roles of the many other lipid species present. The nature of the problem can be more clearly indicated from the 3 1 P nuclear magnetic resonance (NMR) spectra presented in Fig.
eBook - PDF- H. Stephen Stoker(Author)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
Prior to discussing additional types of lipid molecules—emulsification Lipids (Section 8-11), messenger Lipids (Sections 8-12 and 8-13), and protective-coating Lipids (Sec-tion 8-14)—the discussion of membrane Lipids will be extended to include how these types of Lipids interact with each other to form cell membranes. ◀ Living cells contain an estimated 10,000 different kinds of molecules in an aqueous environment confined by a cell membrane. A cell membrane is a lipid-based structure that separates a cell’s aqueous-based interior from the aqueous environment 1. The “steroid nucleus” common to all steroid structures involves a fused-ring system that contains a. four 6-membered rings b. four 5-membered rings c. three 6-membered rings and one 5-membered ring d. no correct response 2. Which of the following types of membrane Lipids has a steroid structure? a. cholesterol b. sphingoglycoLipids c. sphingophosphoLipids d. no correct response 3. Which of the following statements concerning cholesterol is correct ? a. An alcohol functional group is present in its structure. b. The lipoprotein HDL distributes cholesterol to various parts of the human body. c. The cholesterol associated with LDL is often called “good cholesterol.” d. no correct response Section 8-9 Quick Quiz Answers: 1. c; 2. a; 3. a ▶ Cell membranes are also com-monly called plasma membranes because they separate the cyto-plasm (aqueous contents) of a cell from its surroundings. Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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