Lipids - Structure and Function (Lecture) - Biology

CHAPTER 11: Lipids: Structure and Function (LECTURE)  Lesson Outline Lipids – Overview Fatty Acids Saponifiable Lipids Non-Saponifiable Lipids For more info, visit this link https://byjus.com/biology/lipids/  Lipids – Overview A group of heterogenous biomolecules that are insoluble i...

CHAPTER 11: Lipids: Structure and Function (LECTURE)  Lesson Outline Lipids – Overview Fatty Acids Saponifiable Lipids Non-Saponifiable Lipids For more info, visit this link https://byjus.com/biology/lipids/  Lipids – Overview A group of heterogenous biomolecules that are insoluble in water and soluble in non-polar solvents Biological functions: 1. Energy source 2. Insulation of vital organs 3. Covering of nerve fibers 4. Components of cell membrane 5. Chemical messengers (hormones)  Lipids – Overview Classification of Lipids  Lipids – Overview Properties of Lipids Lipids are oily or greasy nonpolar molecules, stored in the adipose tissue of the body. Lipids are a heterogeneous group of compounds, mainly composed of hydrocarbon chains. Lipids are energy-rich organic molecules, which provide energy for different life processes. Lipids are a class of compounds characterized by their solubility in nonpolar solvents and insolubility in water. Lipids are significant in biological systems as they form a mechanical barrier dividing a cell from the external environment known as the cell membrane.  Fatty Acids Monocarboxylic acids that contain long, unbranched hydrocarbon chains, usually 12 to 25 carbons in length Smallest fatty acid – butanoic acid (4 carbons) Saturated FA – no double bonds Monounsaturated FA – has one double bond Polyunsaturated FA – has two or more double bonds  Fatty Acids Fatty Acid Formula Condensed and line-bond formula Eg. Caprylic acid (C8, saturated) CH3CH2CH2CH2CH2CH2CH2COOH CH3―(CH2)6―COOH octanoic acid (8:0)  Fatty Acids Fatty Acid Formula Eg. Palmitoleic acid (C16, monounsaturated) CH3CH2CH2CH2CH2CH2CH=CHCH2CH2CH2CH2CH2CH2CH2COOH CH3(CH2)7CH=CH(CH2)7COOH cis-9-hexadecenoic acid 16:1(Δ9)  Fatty Acids Saturated vs. Polyunsaturated Fatty Acids  Fatty Acids Saturated vs. Polyunsaturated Fatty Acids  Fatty Acids Saturated vs. Polyunsaturated Fatty Acids In unsaturated fatty acids, the stereochemistry at the double bond is usually cis rather than trans. A cis double bond puts a kink/bend in the long-chain hydrocarbon tail, whereas the shape of a trans fatty acid is like that of a saturated fatty acid in its fully extended conformation. Unsaturated fatty acids have lower melting points than saturated ones. Plant oils are liquid at room temperature because they have higher proportions of unsaturated fatty acids than do animal fats, which tend to be solids.  Fatty Acids Trans-fat or Trans Fatty Acids Unsaturated fatty acids that come from either industrial or natural sources. More than 278 000 deaths each year globally can be attributed to intake of industrially produced trans fat. Trans fat clogs arteries, increasing the risk of heart attacks and deaths. Sources: 1. Commercial baked goods, such as cakes, cookies and pies 2. Food shortening 3. Microwave popcorn 4. Frozen pizza 5. Refrigerated dough, such as biscuits and rolls 6. Fried foods, including French fries, doughnuts and fried chicken 7. Nondairy coffee creamer 8. Stick margarine  Fatty Acids Trans-fat or Trans Fatty Acids  Fatty Acids Canola looks good, doesn’t it?  Fatty Acids Olive, coconut, canola, and vegetable oils each provide the same number of calories per tablespoon. Coconut oil, 1 Canola oil, 1 Vegetable oil, 1 Olive oil, 1 tbsp tbsp tbsp tbsp Calories 126 125 126 126 Total fat 14 g 14 g 14 g 14 g Saturated fatty 2.17 g 11.6 g 0.93 g 1.92 g acids Monounsaturate 9.58 g 0.88 g 8.76 g 5.64 g d fatty acids Polyunsaturated 1.33 g 0.24 g 3.54 g 5.64 g fatty acids  Fatty Acids Ten popular cooking oils were put to the test with two different heating trials. The first trial gradually heated each oil to 240ºC (464ºF), the second heated each oil in a deep fryer for 6 hours at 180ºC (356ºF). Each oil was then analyzed for a range of quality factors. Oxidative stability measures how well an oil resists reacting with oxygen and breaking down. Coconut oil scored the highest due to its high saturated fat content. Peanut oil and extra virgin olive oil also scored well.  Fatty Acids Lauric acid omega-6 fatty acid omega-3 too much omega-6 fatty acids can change the way cells react and have harmful effects on cells in the heart and blood vessels Fatty Acids omega-3s “healthy fats” omega-6 fatty acid Arachidonic acid may trigger brain inflammation. High blood levels have been associated with a greater risk of suicide and depressive episodes.  Fatty Acids Essential Fatty Acids Fatty acids that mammals cannot synthesize Eg. Omega-3 and Omega- 6 fatty acids Polyunsaturated fatty acids Essential in normal visual and central nervous system development Omega notation: indicates the position of the first double bond starting from the last carbon  Saponifiable Lipids Produce fatty acid salts upon treatment with base Glyceryl esters: triglycerides, glycerophospholipids Non-glyceryl esters: sphingophospholipids, waxes, glycolipids  Saponifiable Lipids Triacyglycerols/Triglycerides Esters of glycerol and fatty acids Found in adipocytes Triacylglycerols are major energy reserve and the principal neutral derivatives of glycerol found in animals. These molecules consist of a glycerol esterified with three fatty acids.  Saponifiable Lipids Simple vs. Mixed Triacyglycerols/Triglycerides  Saponifiable Lipids Fats vs. Oils FATS TAGs that contain high percentage of saturated fatty acids Solid at room temperature Usually coming from animal sources OILS TAGs that contain high percentage of unsaturated fatty acids Liquid at room temperature Usually coming from plant sources  Saponifiable Lipids Fats vs. Oils  Saponifiable Lipids Glycerophospholipids Common constituents of cell membranes A triester in which First two (2) ―OH groups of glycerol are esterified with fatty acids (need not to be identical) Third ―OH group esterified with a phosphate group that is in turn esterified to an alcohol  Saponifiable Lipids Glycerophospholipids Amphipathic compounds – have hydrophilic heads and hydrophobic tails  Saponifiable Lipids Glycerophospholipids  Saponifiable Lipids Sphingophospholipids Derivatives of ceramide (sphingosine + fatty acid) Fatty acid is connected with the ―NH3+ group via an amide linkage A polar group is usually esterified with the ―OH group on the terminal carbon  Saponifiable Lipids Sphingophospholipids H OC H C H O C H 2C H C H 2 2 N (C H O H CH 3 ) 3 (CH N H H C C OH 2 2C) 3 1 2 3 O H s pHh i n C C H sp h in CH P g o m y go sin H N H H e O CH C e lin C C C H 2O H O H H NH O O C 2 12 C (common C H 2 ) 1constituents 2 of cell H CH3 membranes R C c e rO a C H 3  Saponifiable Lipids Waxes Esters formed from fatty acids and long-chain monohydric alcohols Can be found on: Leaf surfaces – prevents excessive water loss and water absorption which can lead to leaf dissolution Feathers of birds hair  Saponifiable Lipids Glycolipids contain monosaccharides bonded to the ―OH group of ceramide through a glycosidic bond Cerebrosides – glycolipid present in the brain and myelin sheath of the nerves and the sugar component is either galactose or glucose Ganglioside – sugar moiety can be more than one monosaccharides, disaccharides or trisaccharides  Saponifiable Lipids Glycolipids  Saponifiable Lipids Glycolipids Gangliosi de  Non-Saponifiable Lipids Steroids Lipids containing the steroid nucleus which is a fused structure of four rings Cholesterol Bile salts Hormones Vitamin D  Non-Saponifiable Lipids Steroids – Cholesterol Most abundant steroid in the body Can be synthesized in the liver and obtained from diet  Non-Saponifiable Lipids Steroids – Bile Salts Synthesized from cholesterol and released by the gall bladder Emulsify fats and oils to give a greater surface area for lipid digesting enzymes  Non-Saponifiable Lipids Steroids – Steroid Hormones Basically organic compounds synthesized in glands and transported by the bloodstream to various tissues in order to trigger or hinder the desired process  Non-Saponifiable Lipids Eicosanoids Signaling molecules derived from C20 essential fatty acids Act a messengers in the central nervous system Prostaglandins Thromboxanes Leukotrienes  Non-Saponifiable Lipids Eicosanoids – Prostaglandins Function in the regulation of contraction and relaxation of smooth muscle tissues  Non-Saponifiable Lipids Eicosanoids – Thromboxanes Promote formation of blood clots  Non-Saponifiable Lipids Eicosanoids – Leukotrienes Signaling lipids for inflammatory and hypersensivity responses  Non-Saponifiable Lipids Terpenes Hydrocarbons or hydrocarbon derivatives constructed from recurring isoprene units Responsible for the scents and tastes of plant products  Non-Saponifiable Lipids Fat Soluble Vitamins a group of vitamins that are absorbed along with fats in the diet and can be stored in the body's fatty tissue and liver. Because of this storage capability, they do not need to be consumed as frequently as water-soluble vitamins. However, consuming them in excess can lead to toxicity, as the body doesn't easily excrete them.  Non-Saponifiable Lipids Pheromones Chemicals secreted by insects and animals to transmit messages to other members of the species Long chain alkenes with oxygen-containing functional group I don't have a problem if you're trans. I don't have a problem if you're fat. But I do if you’re trans fat. 45