Lipids PDF

LIPIDS Prepared by: Ms. JULIA MHAE B. CELON, LPT. Lecturer I  Lipids are organic compounds that contain hydrogen, carbon, and oxygen atoms, which form the framework for the structure and function of living cells.  Lipids are the polymers of fatty aci...

LIPIDS Prepared by: Ms. JULIA MHAE B. CELON, LPT. Lecturer I  Lipids are organic compounds that contain hydrogen, carbon, and oxygen atoms, which form the framework for the structure and function of living cells.  Lipids are the polymers of fatty acids that contain a long, non-polar hydrocarbon chain with a small polar region containing oxygen. The lipid structure is explained in the diagram below:  FATTY ACIDS They are the simplest lipids with structural formula of R- COOH. They differ from each other by the length of the tail, degree of unsaturation, and position of double bonds. If there is no double bond, the fatty acid is saturated. If there is at least one double bond, the fatty acid is unsaturated.  FATTY ACIDS: ESSENTIAL FATTY ACIDS Linoleic acid , a fatty acid essential for the synthesis of various hormones. Linolenic acid belongs to the group of omega-3 (n-3) fatty acids, which are essential fatty acids for animal nutrition. Due to multiple double bonds.  FATTY ACIDS There are three (3) types of fatty acids according to the number of their double bonds: 1. SATURATED – no double bond 1. MONOUNSATURATED – with one double bond 1. POLYUNSATURATED – with 2-6 double bonds  TRIACYLGLYCEROL They are also called triglycerides which are esters derived from glycerol and three fatty acids molecules They are very hydrophobic, neutral in charge and thus can be stored in anhydrous form. Triacylglycerols, or triglycerides, store energy for the body. Calories are stored in the form of triglycerides in the liver and adipose tissue of the body.  GLYCEROPHOSPHOLIPIDS Glycerophospholipids are composed of glycerol, two fatty acids, phosphate and an amino alcohol. They dominant in cell membranes providing stability, fluidity, and permeability, and they are most abundant lipids in cell membranes.  PHOSPHOLIPID A phospholipid is an amphipathic molecule, meaning it has a hydrophobic part and a hydrophilic part. The fatty acid chains are hydrophobic and do not interact with water, whereas the phosphate-containing group is hydrophilic (because of its charge) and interacts readily with water.  SPHINGOLIPIDS Sphingolipids are enriched in the Central Nervous System (CNS) and display multiple biological functions. They participate in tissue development, cell recognition and adhesion. Biological functions associated with sphingolipids, including cellular regulation, signaling and metabolism.  STEROIDS Steroids are lipids because they are hydrophobic and insoluble in water, but they do not resemble lipids since they have a structure composed of four fused rings. The best known and most abundant steroid in the body is cholesterol. Sex hormones are also steroids. STEROIDS  CHOLESTEROL Cholesterol is a waxy, fat-like substance that's found in all the cells in your body. Your body needs some cholesterol to make hormones, vitamin D, and substances that help you digest foods. But too much cholesterol can cause heart attack and stroke. Two types of cholesterol: LDL and HDL. CHOLESTEROL  WAXES A wax is a simple lipid which is an ester of a long-chain alcohol and a fatty acid. The alcohol may contain from 12- 32 carbon atoms. Waxes are found in nature as coatings on leaves and stems.  Chewing mechanically breaks food into smaller particles and mixes them with saliva. An enzyme called lingual lipase is produced by cells on the tongue (“lingual” means relating to the tongue) and begins some enzymatic digestion of triglycerides, cleaving individual fatty acids from the glycerol backbone.  Cells in the stomach produce another lipase, called gastric lipase that also contributes to enzymatic digestion of triglycerides. Lingual lipase swallowed with food and saliva also remains active in the stomach. But together, these two lipases play only a minor role in fat digestion and most enzymatic digestion happens in the small intestine.  Bile, which is made in the liver and stored in the gallbladder, is released into the duodenum, the first section of the small intestine. Bile salts have both a hydrophobic and a hydrophilic side, so they are attracted to both fats and water. This makes them effective emulsifiers, meaning that they break large fat globules into smaller droplets. Emulsification makes lipids more accessible to digestive enzymes by increasing the surface area for them to act  The pancreas secretes pancreatic lipases into the small intestine to enzymatically digest triglycerides. Triglycerides are broken down to fatty acids, monoglycerides (glycerol backbone with one fatty acid still attached), and some free glycerol. Cholesterol and fat-soluble vitamins do not need to be enzymatically digested.  Bile helps with this process. Bile salts cluster around the products of fat digestion to form structures called micelles, which help the fats get close enough to the microvilli of intestinal cells so that they can be absorbed. The products of fat digestion diffuse across the membrane of the intestinal cells, and bile salts are recycled back to do more work emulsifying fat and forming micelles.  Once inside the intestinal cell, short- and medium-chain fatty acids and glycerol can be directly absorbed into the bloodstream, but larger lipids such as long-chain fatty acids, monoglycerides, fat-soluble vitamins, and cholesterol need help with absorption and transport to the bloodstream. Long- chain fatty acids and monoglycerides reassemble into triglycerides within the intestinal cell, and along with cholesterol and fat-soluble vitamins, are then incorporated into transport vehicles called chylomicrons.  Chylomicrons are large structures with a core of triglycerides and cholesterol and an outer membrane made up of phospholipids, interspersed with proteins (called apolipoproteins) and cholesterol. This outer membrane makes them water-soluble so that they can travel in the aqueous environment of the body. Chylomicrons from the small intestine travel first into lymph vessels, which then deliver them to the bloodstream. THAT’S ALL. THANK YOU!