lipids lecture study
Structure of Lipids
Simple Lipids (Homolipids): These are esters of fatty acids with various alcohols. Examples include fats, oils (esters of fatty acids with glycerol, forming triglycerides), and waxes (esters of fatty acids with long-chain monohydric alcohols).
Triglycerides: Composed of a glycerol molecule esterified with three fatty acid molecules. Can be simple (all three fatty acids are identical) or mixed (the three fatty acids are different).
Compound Lipids (Heterolipids): These are esters of fatty acids with an alcohol, but they also contain other groups in addition to fatty acids and alcohol.
Phospholipids: Contain a phosphate group, fatty acids, and an alcohol (glycerol or sphingosine).
Phosphoglycerides: Glycerol backbone with two fatty acids and a phosphate group. E.g., Lecithins (phosphatidylcholines), Cephalins (phosphatidylethanolamines).
Sphingomyelins: Sphingosine backbone, one fatty acid, and a phosphate group.
Glycolipids: Lipids with a carbohydrate attached by a glycosidic bond. They do not contain phosphate. E.g., Cerebrosides, Gangliosides.
Derived Lipids: These are substances derived from simple and compound lipids by hydrolysis. They include fatty acids, glycerol, steroids, lipid-soluble vitamins, and hormones.
Cholesterol: A primary steroid lipid, crucial for cell membrane structure, precursor to steroid hormones and bile acids. It can exist as free cholesterol or cholesterol esters.
Coprostanol: A reduced form of cholesterol, typically found in feces, formed by bacterial action.
Cholestanol: Another reduced form of cholesterol, differing in saturation at the double bond.
Terpenes: A large class of organic compounds formed from isoprene units. Classified by the number of isoprene units:
Monoterpenes: Two isoprene units (C10), e.g., menthol.
Sesquiterpenes: Three isoprene units (C15).
Diterpenes: Four isoprene units (C20), e.g., retinol (Vitamin A).
Triterpenes: Six isoprene units (C30), e.g., squalene.
Tetraterpenes: Eight isoprene units (C40), e.g., carotenoids.
Properties of Lipids
Chemically Diverse: A broad group of naturally occurring molecules that includes fats, waxes, sterols, fat-soluble vitamins (A, D, E, K), monoglycerides, diglycerides, phospholipids, and others.
Water-insoluble Compounds: They are characterized by their hydrophobic nature, meaning they have little or no affinity for water and tend to aggregate together in aqueous environments.
Comprise primarily of Carbon, Hydrogen, and Oxygen: While primarily composed of C, H, and O, compound lipids like phospholipids and sphingolipids also contain Phosphorus and Nitrogen, respectively.
Non-polymeric nature: Unlike carbohydrates and proteins, lipids are not generally formed from repeating monomeric units into long chains. They consist of distinct structural units like glycerol and fatty acids.
Fatty Acids Components: Long hydrocarbon chains with a carboxyl group.
Saturated Fatty Acids: Contain no carbon-carbon double bonds in their hydrocarbon chain. They are typically solid at room temperature and common in animal fats (e.g., palmitic acid, stearic acid).
Unsaturated Fatty Acids: Contain one or more carbon-carbon double bonds in their hydrocarbon chain. These double bonds introduce kinks, preventing close packing and resulting in liquids at room temperature (oils).
Monounsaturated Fatty Acids (MUFAs): Contain one carbon-carbon double bond (e.g., oleic acid).
Polyunsaturated Fatty Acids (PUFAs): Contain two or more carbon-carbon double bonds (e.g., linoleic acid, linolenic acid).
Biological Importance
Energy Storage: Lipids are highly efficient for energy storage, providing about compared to for carbohydrates and proteins. They serve as a long-term energy reserve.
Provide Essential Fatty Acids: Humans cannot synthesize certain unsaturated fatty acids (e.g., linoleic acid, alpha-linolenic acid) and must obtain them from the diet. These are crucial for growth and overall health.
Structural Components: Integral components of all biological membranes (e.g., cell membranes, mitochondrial membranes), forming the lipid bilayer that provides structural integrity and regulates permeability.
Nervous System Health: Sphingolipids and glycolipids are abundant in the myelin sheath, which insulates nerve fibers and ensures efficient nerve signal transmission.
Sources of Fat-soluble Vitamins: Act as a solvent and carrier for fat-soluble vitamins (A, D, E, K), which are absorbed along with dietary fats. These vitamins play diverse roles in vision, bone health, antioxidant protection, and blood clotting.
Insulation and Protection: Adipose tissue (composed of triglycerides) provides thermal insulation and mechanical protection for vital organs.
Hormone Precursors: Steroid lipids, such as cholesterol, are precursors for steroid hormones (e.g., testosterone, estrogen, cortisol) and bile acids.
Lipids in Diseases
Cardiovascular Diseases (CVD): Elevated levels of certain lipids in the blood (e.g., LDL cholesterol, triglycerides) contribute to atherosclerosis, the hardening and narrowing of arteries, increasing the risk of heart attacks and strokes.
Cancer: Aberrant lipid metabolism and signaling pathways involving lipids have been implicated in various types of cancer growth and progression.
Obesity: Excessive accumulation of body fat, a direct consequence of an imbalance in lipid intake and expenditure, leading to a higher risk of numerous health problems.
Dyslipidemia: An abnormal amount of lipids (e.g., triglycerides, cholesterol) in the blood, often characterized by high LDL ("bad") cholesterol and low HDL ("good") cholesterol, which can result in plaque buildup in blood vessels (atherosclerosis).
Metabolic Syndrome: A cluster of conditions — increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels — that occur together, increasing your risk of heart disease, stroke, and type 2 diabetes. Lipid dysregulation is a key component.
Lipid Solubility
Marginally soluble in water: Due to their predominantly nonpolar hydrocarbon chains, lipids are largely hydrophobic. Small, short-chain fatty acids can show some solubility, but longer chains make them virtually insoluble.
Soluble in organic solvents: Readily dissolve in nonpolar organic solvents such as ether, chloroform, benzene, and acetone, which reflect their nonpolar character.
Fatty Acids
Structure: Long hydrocarbon chains (typically 4-28 carbons, even numbers are most common) with a terminal carboxyl group.\
pKa of carboxyl group: Approximately . At physiological pH (around ), the carboxyl group is deprotonated (), making fatty acids anionic species.
Classifications: Based on the degree of saturation of the hydrocarbon chain.
Saturated: No C=C bonds (e.g., Stearic acid (), Palmitic acid ()). Tend to be solid at room temperature.
Monounsaturated: One C=C bond (e.g., Oleic acid (), common in olive oil). Generally liquid at room temperature.
Polyunsaturated: Two or more C=C bonds (e.g., Linoleic acid (), Linolenic acid (), Arachidonic acid ()). Typically liquid oils.
Triacylglycerols (Triglycerides)
Most abundant lipid: Constitute the major storage form of fat in adipose tissue and are the most prevalent lipid type in the human body.
Composed of: A single glycerol molecule esterified with three fatty acid molecules.
Function: Primarily serve as an efficient energy reserve, storing more than twice the energy per gram compared to carbohydrates or proteins.
Can be Simple: All three fatty acids are identical (e.g., tristearin).
Or Mixed: The three fatty acids are different, which is more common in nature.
Saponification
Definition: The alkaline hydrolysis of triglycerides (fats or oils) into glycerol and fatty acid salts, which are commonly known as soap.
Process: Heating a fat or oil with a strong base (e.g., NaOH or KOH) cleaves the ester bonds, yielding glycerol and the salt of the fatty acids (soap). The soaps thus formed are amphipathic, with a hydrophilic head and a hydrophobic tail, allowing them to emulsify fats.
Phospholipids
Structure: Glycerol esters with two fatty acids and a phosphate group esterified to the third hydroxyl group of glycerol.
Amphipathic Nature: Possess both a hydrophilic (water-loving) head (containing the phosphate group and often a polar head group like choline or ethanolamine) and two hydrophobic (water-fearing) fatty acid tails.
Biological Membranes: Critical for the formation of lipid bilayers, the fundamental structure of all biological membranes. Their amphipathic nature allows them to spontaneously form these bilayers in aqueous environments, with hydrophobic tails facing inward and hydrophilic heads facing outward.
Types: Include phosphoglycerides (e.g., phosphatidylcholine/lecithin, phosphatidylethanolamine/cephalin, phosphatidylserine) and sphingomyelins (based on sphingosine).
Sphingolipids
Structure: A class of lipids that contain a sphingosine backbone (an amino alcohol) instead of glycerol.
Components: Often include one fatty acid attached to the amino group of sphingosine and various head groups attached to the hydroxyl group.
Key Members:
Ceramides: The simplest sphingolipids, consisting of sphingosine and one fatty acid.
Sphingomyelin: A ceramide with a phosphocholine or phosphoethanolamine head group. It is a major component of the myelin sheath surrounding nerve cells.
Glycosphingolipids: Ceramides with a carbohydrate head group (e.g., cerebrosides, gangliosides).
Functions: Important for cell recognition, signaling, and particularly abundant in the nervous system, playing roles in nerve insulation and transmission.
Glycolipids
Structure: Carbohydrates are directly bound to lipids (ceramide backbone) via a glycosidic linkage, without a phosphate group.
Location: Primarily found on the outer surface of the plasma membrane, extending into the extracellular matrix.
Key Components in Nerve Cell Membranes:
Cerebrosides: Simplest glycosphingolipids, with a single sugar residue (glucose or galactose) attached to ceramide.
Gangliosides: More complex glycosphingolipids containing an oligosaccharide chain with one or more sialic acid residues. Highly abundant in myelin and neuronal membranes.
Functions: Play crucial roles in cell recognition, cell adhesion, modulating membrane function, and acting as receptors for hormones and other signaling molecules.
Waxes and Steroids
Waxes:
Structure: Esters of long-chain fatty acids (14-36 carbons) with long-chain alcohols (16-30 carbons).
Function: Highly hydrophobic, serving as waterproof coatings on plants (cuticle) and animals (fur, feathers) and as structural components (e.g., beeswax) and energy storage in some organisms.
Steroids:
Structure: Characterized by a distinctive four-ring core structure (a steroid nucleus: three six-membered rings and one five-membered ring fused together).
Include Cholesterol: The most common steroid in animals, a vital component of cell membranes, modulating fluidity and permeability.
Hormones: Precursor for various steroid hormones, including sex hormones (e.g., testosterone, estrogen, progesterone), adrenocortical hormones (e.g., cortisol, aldosterone), which regulate a wide range of physiological processes.
Bile Salts: Cholesterol derivatives synthesized in the liver, aiding in the emulsification of dietary fats in the small intestine, facilitating their digestion and absorption.
Vitamin D: A steroid derivative, essential for calcium homeostasis and bone health.
Methods of Lipid Analysis
Extraction: Lipids are typically insoluble in water but soluble in organic solvents. Common methods involve using mixtures of polar and nonpolar solvents to separate lipids from other biological macromolecules.
Chloroform/Methanol/Water: A widely used biphasic extraction system (e.g., Folch extraction) that effectively separates lipids from proteins and carbohydrates based on their differing solubilities. Lipids partition into the organic (chloroform) layer.
Chromatography techniques for resolution of lipid components: These methods separate lipid mixtures into individual classes or species based on their differential partitioning between a stationary phase and a mobile phase.
Thin-Layer Chromatography (TLC): A simple and rapid technique used for qualitative and semi-quantitative analysis of lipid classes. Lipids are separated on a silica gel plate.
Gas-Liquid Chromatography (GLC) / Gas Chromatography (GC): Used primarily for the analysis of volatile lipid components, such as fatty acid methyl esters (FAMEs), after chemical derivatization. Provides high resolution and quantitative analysis of individual fatty acids.
High-Performance Liquid Chromatography (HPLC): A versatile method for separating and quantifying various lipid classes (e.g., phospholipids, triglycerides, sterols) without derivatization. Different columns and mobile phases can be used to separate based on polarity, chain length, or saturation.
Mass Spectrometry (MS): Often coupled with GC or HPLC (GC-MS, LC-MS) to provide detailed structural information and precise quantification of lipid molecules. Lipidomics employs these advanced techniques to study the entire lipid profile.
Nuclear Magnetic Resonance (NMR) Spectroscopy: Can be used to determine the structure of lipids and to study their interactions in membranes.
Structure of Lipids
Simple Lipids (Homolipids): These are esters of fatty acids with various alcohols. Examples include fats, oils (esters of fatty acids with glycerol, forming triglycerides), and waxes (esters of fatty acids with long-chain monohydric alcohols).
Triglycerides: Composed of a glycerol molecule esterified with three fatty acid molecules. Can be simple (all three fatty acids are identical) or mixed (the three fatty acids are different).
Compound Lipids (Heterolipids): These are esters of fatty acids with an alcohol, but they also contain other groups in addition to fatty acids and alcohol.
Phospholipids: Contain a phosphate group, fatty acids, and an alcohol (glycerol or sphingosine).
Phosphoglycerides: Glycerol backbone with two fatty acids and a phosphate group. E.g., Lecithins (phosphatidylcholines), Cephalins (phosphatidylethanolamines).
Sphingomyelins: Sphingosine backbone, one fatty acid, and a phosphate group.
Glycolipids: Lipids with a carbohydrate attached by a glycosidic bond. They do not contain phosphate. E.g., Cerebrosides, Gangliosides.
Derived Lipids: These are substances derived from simple and compound lipids by hydrolysis. They include fatty acids, glycerol, steroids, lipid-soluble vitamins, and hormones.
Cholesterol: A primary steroid lipid, crucial for cell membrane structure, precursor to steroid hormones and bile acids. It can exist as free cholesterol or cholesterol esters.
Coprostanol: A reduced form of cholesterol, typically found in feces, formed by bacterial action.
Cholestanol: Another reduced form of cholesterol, differing in saturation at the double bond.
Terpenes: A large class of organic compounds formed from isoprene units. Classified by the number of isoprene units:
Monoterpenes: Two isoprene units (C10), e.g., menthol.
Sesquiterpenes: Three isoprene units (C15).
Diterpenes: Four isoprene units (C20), e.g., retinol (Vitamin A).
Triterpenes: Six isoprene units (C30), e.g., squalene.
Tetraterpenes: Eight isoprene units (C40), e.g., carotenoids.
Properties of Lipids
Chemically Diverse: A broad group of naturally occurring molecules that includes fats, waxes, sterols, fat-soluble vitamins (A, D, E, K), monoglycerides, diglycerides, phospholipids, and others.
Water-insoluble Compounds: They are characterized by their hydrophobic nature, meaning they have little or no affinity for water and tend to aggregate together in aqueous environments.
Comprise primarily of Carbon, Hydrogen, and Oxygen: While primarily composed of C, H, and O, compound lipids like phospholipids and sphingolipids also contain Phosphorus and Nitrogen, respectively.
Non-polymeric nature: Unlike carbohydrates and proteins, lipids are not generally formed from repeating monomeric units into long chains. They consist of distinct structural units like glycerol and fatty acids.
Fatty Acids Components: Long hydrocarbon chains with a carboxyl group.
Saturated Fatty Acids: Contain no carbon-carbon double bonds in their hydrocarbon chain. They are typically solid at room temperature and common in animal fats (e.g., palmitic acid, stearic acid).
Unsaturated Fatty Acids: Contain one or more carbon-carbon double bonds in their hydrocarbon chain. These double bonds introduce kinks, preventing close packing and resulting in liquids at room temperature (oils).
Monounsaturated Fatty Acids (MUFAs): Contain one carbon-carbon double bond (e.g., oleic acid).
Polyunsaturated Fatty Acids (PUFAs): Contain two or more carbon-carbon double bonds (e.g., linoleic acid, linolenic acid).
Biological Importance
Energy Storage: Lipids are highly efficient for energy storage, providing about compared to for carbohydrates and proteins. They serve as a long-term energy reserve.
Provide Essential Fatty Acids: Humans cannot synthesize certain unsaturated fatty acids (e.g., linoleic acid, alpha-linolenic acid) and must obtain them from the diet. These are crucial for growth and overall health.
Structural Components: Integral components of all biological membranes (e.g., cell membranes, mitochondrial membranes), forming the lipid bilayer that provides structural integrity and regulates permeability.
Nervous System Health: Sphingolipids and glycolipids are abundant in the myelin sheath, which insulates nerve fibers and ensures efficient nerve signal transmission.
Sources of Fat-soluble Vitamins: Act as a solvent and carrier for fat-soluble vitamins (A, D, E, K), which are absorbed along with dietary fats. These vitamins play diverse roles in vision, bone health, antioxidant protection, and blood clotting.
Insulation and Protection: Adipose tissue (composed of triglycerides) provides thermal insulation and mechanical protection for vital organs.
Hormone Precursors: Steroid lipids, such as cholesterol, are precursors for steroid hormones (e.g., testosterone, estrogen, cortisol) and bile acids.
Lipids in Diseases
Cardiovascular Diseases (CVD): Elevated levels of certain lipids in the blood (e.g., LDL cholesterol, triglycerides) contribute to atherosclerosis, the hardening and narrowing of arteries, increasing the risk of heart attacks and strokes.
Cancer: Aberrant lipid metabolism and signaling pathways involving lipids have been implicated in various types of cancer growth and progression.
Obesity: Excessive accumulation of body fat, a direct consequence of an imbalance in lipid intake and expenditure, leading to a higher risk of numerous health problems.
Dyslipidemia: An abnormal amount of lipids (e.g., triglycerides, cholesterol) in the blood, often characterized by high LDL ("bad") cholesterol and low HDL ("good") cholesterol, which can result in plaque buildup in blood vessels (atherosclerosis).
Metabolic Syndrome: A cluster of conditions — increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels — that occur together, increasing your risk of heart disease, stroke, and type 2 diabetes. Lipid dysregulation is a key component.
Lipid Solubility
Marginally soluble in water: Due to their predominantly nonpolar hydrocarbon chains, lipids are largely hydrophobic. Small, short-chain fatty acids can show some solubility, but longer chains make them virtually insoluble.
Soluble in organic solvents: Readily dissolve in nonpolar organic solvents such as ether, chloroform, benzene, and acetone, which reflect their nonpolar character.
Fatty Acids
Structure: Long hydrocarbon chains (typically 4-28 carbons, even numbers are most common) with a terminal carboxyl group.\
pKa of carboxyl group: Approximately . At physiological pH (around ), the carboxyl group is deprotonated (), making fatty acids anionic species.
Classifications: Based on the degree of saturation of the hydrocarbon chain.
Saturated: No C=C bonds (e.g., Stearic acid (), Palmitic acid ()). Tend to be solid at room temperature.
Monounsaturated: One C=C bond (e.g., Oleic acid (), common in olive oil). Generally liquid at room temperature.
Polyunsaturated: Two or more C=C bonds (e.g., Linoleic acid (), Linolenic acid (), Arachidonic acid ()). Typically liquid oils.
Triacylglycerols (Triglycerides)
Most abundant lipid: Constitute the major storage form of fat in adipose tissue and are the most prevalent lipid type in the human body.
Composed of: A single glycerol molecule esterified with three fatty acid molecules.
Function: Primarily serve as an efficient energy reserve, storing more than twice the energy per gram compared to carbohydrates or proteins.
Can be Simple: All three fatty acids are identical (e.g., tristearin).
Or Mixed: The three fatty acids are different, which is more common in nature.
Saponification
Definition: The alkaline hydrolysis of triglycerides (fats or oils) into glycerol and fatty acid salts, which are commonly known as soap.
Process: Heating a fat or oil with a strong base (e.g., NaOH or KOH) cleaves the ester bonds, yielding glycerol and the salt of the fatty acids (soap). The soaps thus formed are amphipathic, with a hydrophilic head and a hydrophobic tail, allowing them to emulsify fats.
Phospholipids
Structure: Glycerol esters with two fatty acids and a phosphate group esterified to the third hydroxyl group of glycerol.
Amphipathic Nature: Possess both a hydrophilic (water-loving) head (containing the phosphate group and often a polar head group like choline or ethanolamine) and two hydrophobic (water-fearing) fatty acid tails.
Biological Membranes: Critical for the formation of lipid bilayers, the fundamental structure of all biological membranes. Their amphipathic nature allows them to spontaneously form these bilayers in aqueous environments, with hydrophobic tails facing inward and hydrophilic heads facing outward.
Types: Include phosphoglycerides (e.g., phosphatidylcholine/lecithin, phosphatidylethanolamine/cephalin, phosphatidylserine) and sphingomyelins (based on sphingosine).
Sphingolipids
Structure: A class of lipids that contain a sphingosine backbone (an amino alcohol) instead of glycerol.
Components: Often include one fatty acid attached to the amino group of sphingosine and various head groups attached to the hydroxyl group.
Key Members:
Ceramides: The simplest sphingolipids, consisting of sphingosine and one fatty acid.
Sphingomyelin: A ceramide with a phosphocholine or phosphoethanolamine head group. It is a major component of the myelin sheath surrounding nerve cells.
Glycosphingolipids: Ceramides with a carbohydrate head group (e.g., cerebrosides, gangliosides).
Functions: Important for cell recognition, signaling, and particularly abundant in the nervous system, playing roles in nerve insulation and transmission.
Glycolipids
Structure: Carbohydrates are directly bound to lipids (ceramide backbone) via a glycosidic linkage, without a phosphate group.
Location: Primarily found on the outer surface of the plasma membrane, extending into the extracellular matrix.
Key Components in Nerve Cell Membranes:
Cerebrosides: Simplest glycosphingolipids, with a single sugar residue (glucose or galactose) attached to ceramide.
Gangliosides: More complex glycosphingolipids containing an oligosaccharide chain with one or more sialic acid residues. Highly abundant in myelin and neuronal membranes.
Functions: Play crucial roles in cell recognition, cell adhesion, modulating membrane function, and acting as receptors for hormones and other signaling molecules.
Waxes and Steroids
Waxes:
Structure: Esters of long-chain fatty acids (14-36 carbons) with long-chain alcohols (16-30 carbons).
Function: Highly hydrophobic, serving as waterproof coatings on plants (cuticle) and animals (fur, feathers) and as structural components (e.g., beeswax) and energy storage in some organisms.
Steroids:
Structure: Characterized by a distinctive four-ring core structure (a steroid nucleus: three six-membered rings and one five-membered ring fused together).
Include Cholesterol: The most common steroid in animals, a vital component of cell membranes, modulating fluidity and permeability.
Hormones: Precursor for various steroid hormones, including sex hormones (e.g., testosterone, estrogen, progesterone), adrenocortical hormones (e.g., cortisol, aldosterone), which regulate a wide range of physiological processes.
Bile Salts: Cholesterol derivatives synthesized in the liver, aiding in the emulsification of dietary fats in the small intestine, facilitating their digestion and absorption.
Vitamin D: A steroid derivative, essential for calcium homeostasis and bone health.
Methods of Lipid Analysis
Extraction: Lipids are typically insoluble in water but soluble in organic solvents. Common methods involve using mixtures of polar and nonpolar solvents to separate lipids from other biological macromolecules.
Chloroform/Methanol/Water: A widely used biphasic extraction system (e.g., Folch extraction) that effectively separates lipids from proteins and carbohydrates based on their differing solubilities. Lipids partition into the organic (chloroform) layer.
Chromatography techniques for resolution of lipid components: These methods separate lipid mixtures into individual classes or species based on their differential partitioning between a stationary phase and a mobile phase.
Thin-Layer Chromatography (TLC): A simple and rapid technique used for qualitative and semi-quantitative analysis of lipid classes. Lipids are separated on a silica gel plate.
Gas-Liquid Chromatography (GLC) / Gas Chromatography (GC): Used primarily for the analysis of volatile lipid components, such as fatty acid methyl esters (FAMEs), after chemical derivatization. Provides high resolution and quantitative analysis of individual fatty acids.
High-Performance Liquid Chromatography (HPLC): A versatile method for separating and quantifying various lipid classes (e.g., phospholipids, triglycerides, sterols) without derivatization. Different columns and mobile phases can be used to separate based on polarity, chain length, or saturation.
Mass Spectrometry (MS): Often coupled with GC or HPLC (GC-MS, LC-MS) to provide detailed structural information and precise quantification of lipid molecules. Lipidomics employs these advanced techniques to study the entire lipid profile.
Nuclear Magnetic Resonance (NMR) Spectroscopy: Can be used to determine the structure of lipids and to study their interactions in membranes.
Summary
Lipid Structure, Classification, and Functions
Structure: Primarily composed of C, H, and O; some contain P and N. Non-polymeric and largely hydrophobic.
Classification: Divided into Simple Lipids (e.g., fats, oils, waxes), Compound Lipids (e.g., phospholipids, glycolipids), and Derived Lipids (e.g., fatty acids, steroids, vitamins).
Functions: Energy storage, structural components of membranes, source of essential fatty acids, nervous system health, insulation, protection, and hormone precursors.
Saturated and Unsaturated Fatty Acids
Structure: Long hydrocarbon chains with a terminal carboxyl group.
Saturated Fatty Acids: No carbon-carbon double bonds; typically solid at room temperature (e.g., palmitic, stearic acid).
Unsaturated Fatty Acids: One or more carbon-carbon double bonds, causing kinks; liquid at room temperature.
Monounsaturated (MUFAs): One C=C bond (e.g., oleic acid).
Polyunsaturated (PUFAs): Two or more C=C bonds (e.g., linoleic, linolenic acid).
Triacylglycerols (Triglycerides)
Composition: A single glycerol molecule esterified with three fatty acid molecules.
Classification: Can be Simple (all three fatty acids are identical) or Mixed (different fatty acids).
Biological Importance: Most abundant storage form of fat in adipose tissue; serve as an efficient, long-term energy reserve (approximetly ).
Phospholipids and Examples
Definition: Glycerol (or sphingosine) esters with two fatty acids and a phosphate group. They are amphipathic.
Examples: Phosphoglycerides (Lecithins/phosphatidylcholines, Cephalins/phosphatidylethanolamines) and Sphingomyelins.
Sphingolipids and Glycolipids Examples
Sphingolipids Examples: Ceramides, Sphingomyelin, Glycosphingolipids (Cerebrosides, Gangliosides).
Glycolipids Examples: Cerebrosides, Gangliosides.
Cholesterol, Waxes, and Vitamin D
Cholesterol: A primary steroid lipid, crucial for cell membrane structure and precursor for steroid hormones and bile acids.
Waxes: Esters of long-chain fatty acids and long-chain alcohols, providing hydrophobic coatings and structural support.
Vitamin D: A steroid derivative essential for calcium homeostasis and bone health.