BIOQUI - 27/06/2023

Lípidos: Funciones y Clasificaciones

Introducción a los Lípidos

• Se abordarán consideraciones generales sobre los lípidos, incluyendo su función, clasificación y su papel en la dieta, así como procesos metabólicos como la beta-oxidación y cetogénesis.

Estructura de la Membrana Celular

• Los lípidos son abundantes en la membrana celular, que se describe según la teoría del mosaico fluido de Nicholson. Esta teoría establece que la membrana es una doble capa de lípidos con proteínas integrales y periféricas unidas a oligosacáridos formando glucoproteínas o glucolípidos.

• La doble capa de lípidos es fluida; los lípidos tienen una cabeza polar hidrófila y colas formadas por ácidos grasos que son hidrofóbicas, creando un entorno interno diferente al externo.

Tipos de Lípidos

• Los lípidos incluyen grasas, ceras y aceites. Estos son ésteres de glicerol con ácidos orgánicos. El glicerol es el alcohol más común que se esterifica con ácidos grasos para formar estos compuestos.

• Las grasas y aceites contienen entre seis a diez ácidos grasos, mientras que las ceras utilizan diferentes alcoholes en lugar de glicerol, lo cual las diferencia.

Clasificación de Lípidos

• Los lípidos pueden clasificarse por estructura (simples vs complejos), función o características físicas. Por ejemplo:

• Lípidos simples: Ácidos grasos.

• Lípidos complejos: Fosfoglicéridos (con fosfatos), glucolípidos (con azúcares), lipoproteínas (unidas a proteínas).

• Es importante notar que los lípidos vegetales no contienen colesterol, mientras que los animales sí lo hacen. Esto implica diferencias significativas en sus propiedades nutricionales.

Funciones Metabólicas

• Los ácidos grasos son considerados los más importantes dentro del grupo de los lípidos debido a su rol como combustible metabólico y componentes esenciales en otras clases de lípidos.

• Existen ácidos grasos esenciales que el cuerpo no puede sintetizar; deben ser obtenidos a través de la dieta. Ejemplos incluyen el ácido palmítico.

Almacenamiento Energético

• Los triacilglicéridos (o triglicérides), formados por tres ácidos grasos unidos al glicerol mediante enlaces éster, son las principales formas de almacenamiento energético en el cuerpo humano.

Understanding Lipids and Their Functions

Overview of Membrane Components

• Membranes contain various lipids, including phospholipids like arachidonic acid and inositol. Phosphatidylinositol is highlighted as a significant phospholipid.

• Key phospholipids include phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine. Sphingolipids differ from triglycerides by having sphingosine instead of glycerol as their alcohol component.

Importance of Cholesterol

• Sphingomyelin is an essential sphingolipid found in membranes and myelin sheaths surrounding nerve fibers, crucial for nerve impulse transmission.

• Cholesterol acts as a steroid component of membranes, enhancing membrane fluidity. Higher cholesterol levels increase membrane mobility.

• Cholesterol is vital for producing bile salts and steroid hormones such as testosterone, progesterone, estrogen, and aldosterone.

Classification of Lipids

• Lipid classifications include non-polar lipids (cholesterol), polar lipids (phospholipids), glycolipids (e.g., cerebrosides), which play physiological roles in diseases related to excess or absence.

• Glycolipids are categorized into cerebrosides and sulfatides; they have significant physiological implications.

Fatty Acids: Structure and Types

• Fatty acids consist mainly of carbon, hydrogen, and oxygen; some may also contain phosphorus or sulfur. They feature a carboxylic acid group at one end and a methyl group at the other.

• Fatty acids can be saturated or unsaturated based on the presence of double bonds between carbon atoms. Unsaturated fatty acids have one or more double bonds.

Transport Mechanisms for Fatty Acids

Understanding Fatty Acids and Their Configurations

Transport and Storage of Fatty Acids

• Fatty acids are primarily transported in the bloodstream bound to albumin. In adipose tissue, they are stored or esterified by linking to glycerol, forming monoacylglycerols or diacylglycerols depending on the number of fatty acids attached.

Cis vs. Trans Configurations

• Most biological fatty acids have a cis configuration, where the double bond is positioned at the same level as the carboxylate group. This differs from trans configurations, where the structure is oriented oppositely.

• Trans fatty acids are often produced through hydrogenation processes in oils and fats, leading to structural changes that can be harmful.

Health Implications of Trans Fats

• Margarine is a classic example containing trans fatty acids due to its production process from liquid oils into solid forms via hydrogenation.

• Concerns have been raised about trans fats contributing to cellular aging and potential cancer risks; however, enzymes exist that can convert trans back to cis configurations.

Controversy Surrounding Margarine Use

• The debate over margarine's safety continues due to its high trans fat content, which is linked with increased cholesterol levels and health issues like aging and cancer.

Classification of Fatty Acids by Chain Length

• Fatty acids are categorized based on carbon chain length: short (2-4 carbons), medium (6-10), and long (12-26). The body can synthesize up to 16-carbon chains like palmitic acid but not beyond this limit.

Saturated vs. Unsaturated Fatty Acids

• Saturated fatty acids contain only single bonds between carbon atoms while unsaturated ones have one or more double bonds. This distinction has biological implications for health.

Biological Effects of Different Types of Fatty Acids

• Unsaturated fatty acids are generally considered beneficial for health, whereas saturated fats may predispose individuals to lipid-related diseases.

Key Types of Unsaturated Fatty Acids

• Important unsaturated fatty acids include:

• Monounsaturated: Oleic acid (found in olives).

• Polyunsaturated: Omega-3 (alpha-linolenic acid), Omega-6 (linoleic acid), EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid).

Benefits of Long-chain Polyunsaturated Fatty Acids

• EPA and DHA are highlighted for their potential health benefits, including lowering cholesterol levels and reducing lipid-related diseases.

Understanding Omega Designations

• Omega designations refer to the position of double bonds in relation to the terminal methyl group; omega-three indicates a double bond at the third carbon from this end.

Understanding Fatty Acids and Their Importance

Types of Fatty Acids

• The perfect monounsaturated fatty acid has a single unsaturation at the exact midpoint, specifically at carbon nine when counted from the carboxyl group.

• Linoleic acid contains two unsaturations, while linolenic acid has three. These acids differ in their number of double bonds.

• Oleic acid is derived from olives and has one double bond; linoleic and linolenic acids are essential fatty acids that must be consumed through diet.

Essential Fatty Acids and Their Sources

• Arachidonic acid, with 20 carbons and four unsaturations, is crucial as it leads to the production of prostanoids and leukotrienes, which are significant in lipid-related diseases.

• Various saturated fatty acids are mentioned: capric (10C), caprylic (8C), lauric (12C), myristic (14C), palmitic (16C), stearic (18C), arachidonic (20C), and lignoceric (24C).

Saturated vs. Unsaturated Fats in Oils

• Olive oil is noted for having a high proportion of saturated fats compared to unsaturated fats; palm oil has fewer saturates.

• Sunflower oil, commonly consumed, has a higher ratio of saturated to unsaturated fats than recommended; olive oil should be preferred due to its lower saturated fat content.

Key Unsaturated Fatty Acids

• Important unsaturated fatty acids include palmitoleic, oleic, linoleic, linolenic, and arachidonic acids. Arachidonic acid is particularly significant due to its role in eicosanoid structures.

• Arachidonic acid is classified as an eicosatetraenoic acid because it contains four double bonds located at carbons five, eight, eleven, and fourteen.

Omega Classification of Fatty Acids

• Monounsaturated fatty acids have one double bond; polyunsaturated have two or more. The first carbon next to the functional group is known as Delta.

• Counting from the methyl end identifies omega positions: for example, omega-six indicates a double bond at carbon six.

Health Implications of Omega Fatty Acids

• Research suggests that diets rich in omega-three fatty acids correlate with better health outcomes including reduced aging effects and lower cholesterol levels.

• Omega-three sources are widely available in both plant-based foods and animal products; they provide notable nutritional benefits linked to heart health.

Understanding Omega Fatty Acids

Overview of Omega Fatty Acids

• Discussion begins with cold-water fish, such as salmon and cod, highlighting their significance in omega fatty acids.

• Introduction of palmitoleic acid (C16:1), linoleic acid (C18:2), and alpha-linolenic acid (omega-3) from flaxseed as essential sources of omega fatty acids.

• Oleic acid is identified as an omega-9 monounsaturated fat primarily found in olives; arachidonic acid is noted for its role as an omega-6 fatty acid.

Importance of Omega-3 Fatty Acids

• Emphasis on the necessity of omega-3 fatty acids for biological functions, including cellular membrane formation and hormone production.

• Highlighting the critical roles of omega-3 in immune system function, retinal health, neuronal activity, and neurotransmission post-COVID pandemic.

Health Benefits Associated with Omega Fatty Acids

• Specific benefits attributed to omega-3 include improved circulatory health, anti-inflammatory properties, potential cancer prevention, menstrual pain relief, mental health support, and assistance during pregnancy.

Sources of Omega Fatty Acids

• Cold-water fish like bluefish and cod are cited as excellent sources; plant oils also contribute significantly to dietary intake.

Additional Sources of Omega Fatty Acids