Lipidos

• Fatty acid

  A carboxylic acid containing a long hydrocarbon chain. Fatty acids are an important fuel source as well as a key component of membrane lipids.
• Fatty acid chain length

  14-22 Carbons
• Unsaturated fatty acids

  • Formed by double or triple covalent bonds, provide fluidity
• Ácidos grasos insaturados

  Formados por un doble o enlaces triple
• Lípidos de la membrana

  • Fosfolípidos
  • Esfingolípidos
  • Glicolípidos
  • Colesterol
• Fosfolípidos

  • Formados por 2 cadenas de ácidos grasos, mediante enlaces éster, 1 alcohol y fosfato
  • Glicerofosfolípidos: glicerol backbone
  • Esfingolípidos: esfingosina backbone, rigidez membranas
• Triglicéridos

  Concentración de ácidos grasos en la sangre debe ser baja, son la manera de almacenar energía más eficiente, forman el tejido adiposo
• Esfingomielina


  Se encarga de recubrir la membrana de las células nerviosas, buen aislante, alta capacidad de reaccionar con el colesterol reduciendo el gasto de energía entre la sinapsis nerviosa
• Glicolípidos

  Compuestos por carbohidratos, orientados de manera asimétrica en la membrana, con la parte de azúcares orientada de manera extracelular, más comunes en plantas y bacterias
• Colesterol


  Modula la fluidez de la membrana, da propiedades de rigidez, contribuye a la síntesis de ácidos biliares y hormonas, disminuye daños de oxidación, pero su acumulación puede generar arteriosclerosis
• Esteroides


  Moléculas extremadamente hidrófobas formadas por 4 anillos de carbono, precursores de hormonas esteroides como glucocorticoides, mineralocorticoides, andrógenos y estrógenos
• Funciones hormonales

  1. Glucocorticoides (e.g., cortisol), que modulan procesos metabólicos, reacciones inflamatorias y respuestas al estrés

  2. Mineralocorticoides (e.g., aldosterona), que regulan la excreción de sal y agua

  3. Andrógenos y estrógenos, que influyen en el desarrollo sexual y las funciones reproductivas
• Isoprenoides

  Clase grande de lípidos que sirven múltiples funciones en animales y plantas, incluyen ubiquinona, plastoquinona, vitaminas A, K y E
• Membranas

  • Asimétricas, con más fosfatidilcolina y esfingomielina en el exterior, y más fosfatidiletanolamina y fosfatidilserina en el interior, organización regida por interacciones de Van der Waals y efecto hidrofóbico
• Propiedades del agua

  Elevada temperatura de fusión y ebullición, molécula polar con capacidad de formar puentes de hidrógeno, alta capacidad térmica, buena conductividad
• Respiración

  El aire va a los pulmones y la sangre al pulmón, en los tejidos la sangre capta oxígeno y libera CO2, el CO2 reacciona con el agua formando ácido carbónico, bajando el pH, lo que aumenta la afinidad de la hemoglobina por el oxígeno, que es captado y liberado en los tejidos
• Disolución de moléculas en agua

  Aumenta la entropía del agua, que intenta minimizar este aumento formando estructuras como micelas y bicapas lipídicas
• Estructura de membranas

  • Bicapa lipídica fluida con proteínas, asimetría y distribución lateral de lípidos, existencia de flipasas que modifican la composición de la membrana
• Las membranas están en estado de no equilibrio, con flujos de materia y energía a través de ellas
• Lipids


  Vital components of all cells, a diverse group of nonpolar substances that are poorly or not at all water-soluble but dissolve readily in many organic solvents
• Lipids

  • Unlike nucleic acids, proteins, and carbohydrates, they do not have unifying structural features
  • They are essential constituents of biological membranes
  • The acyl chains of lipids serve as energy sources
  • A number of cell signaling processes involve lipids
• Lipid Classification

  • Fatty acids
  • Saturated fatty acids
  • Unsaturated fatty acids
  • Triacylglycerols
  • Glycerophospholipids
  • Phospholipases
  • Plasmalogens
  • Sphingolipids
  • Steroids
  • Isoprenoids
  • Eicosanoids
• Fatty acids


  Common components of other lipids, where they occur in ester or amide linkages, straight-chain carboxylic acids usually having between 14 and 22 carbons
• Saturated fatty acids

  • Contain no double bonds and are highly flexible molecules that tend to assume a fully extended conformation
  • In the pure compound, neighboring saturated fatty acyl chains pack together tightly, causing fatty acid melting points to increase as chain length increases
• Unsaturated fatty acids

  • The double bonds nearly always have the cis configuration, which introduces a 30° bend in the acyl chain, preventing them from packing together as closely as saturated fatty acids
  • The melting point of an unsaturated fatty acid is always lower than the melting point for a saturated fatty acid with the same number of carbons
• Triacylglycerols

  Contain three fatty acids esterified to the hydroxyl groups of d-glycerol, serve as energy reserves in plants and animals
• Triacylglycerols

  • Generally contain more than one type of fatty acyl group, mixtures of which may be fats (solid at room temperature) or oils (liquid at room temperature)
  • The highly reduced nature of triacylglycerols makes them an efficient metabolic energy store
• Glycerophospholipids


  The major lipid constituents of biological membranes, composed of d-glycerol with fatty acids esterified to C1 and C2 and a phosphate group esterified.
• Phospholipases


  Enzymes that hydrolyze glycerophospholipids
• Sphingolipids

  All contain a long-chain nitrogen-containing alcohol named sphingosine, including sphingomyelin, cerebrosides, and gangliosides
• Steroids


  hidrophobic molecules, phosphate and and alcohol 4 fused-ring system, including cholesterol and steroid hormones
• Isoprenoids


  lipids multiple f(x), example: vitamins A, K, and E
• Eicosanoids

  Derived from the highly unsaturated C20 lipid arachidonic acid, including prostaglandins, thromboxanes, leukotrienes, and lipoxins
• Lipid bilayers

  • The physical properties of lipids in aqueous solution cause them to aggregate, with polar head groups in contact with the aqueous environment and hydrophobic tails forming the interior
  • Amphiphiles with two hydrocarbon tails, such as glycerophospholipids, form disklike micelles that are lipid bilayers
  • Lipids readily diffuse laterally in the plane of the bilayer, but transverse diffusion or flip-flop occurs infrequently
  • Bilayer fluidity is a function of temperature, with a transition temperature depending on bilayer composition and the presence of cholesterol
• Cholesterol

  • Stabilizes the bilayer over a range of temperatures, interfering with fatty acyl chain mobility at high temperatures and preventing tight packing at low temperatures
• Membrane protein types

  • Integral proteins
  • Lipid-linked proteins
  • Peripheral proteins
• Integral membrane proteins

  • Contribute to the asymmetry of a biological membrane, with transmembrane domains
• Lipid-linked proteins

  Covalently linked to a lipid moiety, such as an isoprenoid, glycosylphosphatidylinositol, or fatty acyl group, which provides a hydrophobic anchor in the membrane
• Membrane components

  • Some regions strongly associate with nonpolar membrane components via hydrophobic effects
  • Hydrophilic portions extend into aqueous surroundings
• Membrane proteins

  • Contribute to the asymmetry of a biological membrane
  • Either present on one side of a membrane or, if they extend through it, are oriented in only one direction