PHTH1011 Lipids Definition, Types and Functions PDF

PHTH1011 Lipids Definition, Types and Functions by Professor Rachael Irving Objectives ▪ Defining the structures of common types of lipids ▪ Outlining the basic functions of lipids ▪ Looking at the inter-play of structure and function ▪ Understanding the role of bimolecular sheets in gaseous exchang...

PHTH1011 Lipids Definition, Types and Functions by Professor Rachael Irving Objectives ▪ Defining the structures of common types of lipids ▪ Outlining the basic functions of lipids ▪ Looking at the inter-play of structure and function ▪ Understanding the role of bimolecular sheets in gaseous exchange ▪ Be able to name a few diseases associated with lipid storage Lipids(definition) 1. Li lipids are a chemically diverse group of organic compounds, the common and defining feature of which is their insolubility in water. 1. A lipid can therefore be defined as any fat-soluble , organic molecule. 2. A lipid is highly soluble in non-polar solvents (Chloroform and ether). 3. lipids water-insolubility contributes to much of the complexity in their digestion, transport, and metabolism (functions). 4. Lipids are essential to the overall energy economy of the cell. Types of Lipids : 1. (Fatty acids) ▪Fatty acids are long hydrocarbon chains of various length and degrees of un-saturation terminating with carboxylic acid groups. ▪Fatty acids carbon atoms are numbered starting at the Carboxyl terminus. ▪The systematic name is derived from the name of its parent hydrocarbon by the substitution of oic for the final e. ▪For example C18 saturated fatty acid is called octadecanoic because the parent hydrocarbon is octadecane. A C18 fatty acid with one double bond is called octadecenoic. Example of Fatty Acids : Octadecadienoic Acid Saturated/Unsaturated Fatty Acids Saturated fatty acids : Fatty acids with have no double bonds. They carry the maximum possible number of hydrogen atoms. Example Stearic Acid. Unsaturated fatty acids : Fatty acids that lack hydrogen atoms and have at least one double bonds. Example Linoleic Acid. Cis and trans-Fatty Acids ▪A cis fatty acid has its hydrogen atoms on the same side of the double bonds. ▪A trans- fatty acids has its hydrogen atoms on opposite side of the double bond. Essential/Non-Essential Fatty Acids. ▪Non-essential Fatty Acids are produced by the body. ▪Essential Fatty Acids are derived from the diets, these acids are not produced by the body but are necessary for vital functions. Examples linoleic (C18 : 2 ω6) and αlinolenic (C18 : 3 ω3). 2. (Triglycerides) ▪A triglyceride is formed from a molecule of glycerol and three fatty acids. ▪Triglycerides are major components of very low density lipoprotein (VLDL) and chylomicrons. ▪Triglycerides are important in metabolism as energy sources and transporters of dietary fat. 3. (Phospholipids) ▪ Phospholipids contain one or more fatty acids. The fatty acid is attached to, a phosphate and an alcohol. ▪ Phospholipids may be attached to glycerol, a 3 carbon alcohol or sphingosine. Sphingosine is an amino alcohol with a long unsaturated hydrocarbon carbon chain. ▪ Those Phospholipids derived from glycerols are called phosphoglycerides. Example cardiolipin found in the heart. ▪ Those derived from sphingosine is called Sphingomyelin. Sphingomyelin is found in the brain. 4. (Glycolipids) ▪Glycolipids are sugar containing lipids. ▪Glycolipids are derived from sphingosine. ▪Glycolipids differ from sphingomyelin in the identity of the unit that is linked to the primary hydroxyl group of the sphingosine backbone. The simplest glycolipid is called a cerebroside. It contains a sugar residue of glucose or galactose. ▪ Cerebroside is found in neural tissue. 5. Sterol lipids : (1)Cholesterol ▪ Cholesterol is built from 4 linked hydrocarbon rings. ▪ A hydrocarbon tail is linked to the steroid at one end and a hydroxyl group is attached at the other end. ▪ In membranes, the orientation of the molecule is parallel to the fatty acids chains of the Phospholipids and the hydroxyl group interacts with the nearby Phospholipid head groups. Structure of Cholesterol: 4 linked hydrocarbon rings Sterol Lipids: (2)Bile Salt Bile Salt has the 4 linked hydrocarbon rings plus : Taurine or Glycine or Both Example of Bile Salt Originates from cholesterol. Lipid Profile High Density lipoprotein Cholesterol-HDL-C (>1.2mmol/l Low Density Lipoprotein Cholesterol -LDL-C (2.4mmol/l) Triglyceride (