Lecture 4 - Lipids PDF

SCHOOL OF MEDICINE & PUBLIC HEALTH LECTURE - LIPIDS BMMB110 (Biology 1.1) Motivational Corner Words of Wisdom 1. As long as you think the problem is out there, that very thought is the problem. 2. Building trust takes a long...

SCHOOL OF MEDICINE & PUBLIC HEALTH LECTURE - LIPIDS BMMB110 (Biology 1.1) Motivational Corner Words of Wisdom 1. As long as you think the problem is out there, that very thought is the problem. 2. Building trust takes a long time, breaking it happens in an instance, repairing it takes forever. [Ancient Chinese Wisdom, Lao Tzu, n.d.] 3. The Fear of the Lord [God Almighty] is the beginning of Knowledge [Proverbs 1:7] Lipids Loading… Lecture slides Compiled by Dr. Stephen  M. Manchishi What elements make up lipids? A. Carbon and Hydrogen. B. Carbon, Hydrogen and Oxygen. C. Carbon, Hydrogen, Oxygen and Nitrogen. D. Carbon, Hydrogen, Oxygen, Nitrogen and Sulphur.  Lipids are nonpolar organic compounds made of C, H and O. Loading… Contain more C-H bonds (almost no oxygen) What are lipids? Varied group of chemicals All organic Esters formed by fatty combining with an alcohol  Lipids are insoluble in water because ….  Fats and oils The most familiar lipids are fats and oils  Fats and oils are chemically very similar Fats (solid at room temperature) are mainly from animal sources oils (liquid at room temperature) are from plant sources  Contain two types of organic chemical substances: glycero fatty acids. l  Loading… Fatty acids  A series of acids, some of which are found in fats (lipids) Contain a carboxyl group (-COOH) at one end (head) long hydrocarbon chain (tail)  The length of hydrocarbon tail can differ; usually 15 – 17 carbon atoms long. Fatty acids are lipids because of the nonpolar character of their hydrocarbon ‘tails’, which dominate their properties  The tail may be saturated (contains only single bonds between carbon atoms) or unsaturated (contains double bonds between carbon atoms). The double bond causes a kink (bend) in the tail  If there is more than one double bond in a fatty acid, it is described as polyunsaturated. If there is only one, it is monounsaturated.  Whether the fatty acid is saturated or unsaturated accounts for the different chemical properties of a lipids  General formula of saturated fatty acid is (CH3(CH2)nCOOH)  Oleic acid Stearic acid 1. Write down the formula of the fatty acid below. 2. Draw the structure of the fatty acid with the following formula: C18 H34 O2  Which of the following is monounsaturated fatty acid? 1. C18 H36 O2 2. C18 H34 O2 3. C18 H32 O2 4. C18 H30 O2 5. C18 H28 O2  Unsaturated fatty acids DO NOT contain the maximum possible amount of hydrogen. They form unsaturated lipids They double bond makes the fatty acid/lipid more easy to melt Most oils are unsaturated  Saturated fatty acids have higher melting points compared to unsaturated fatty acids of the corresponding size  Unsaturated fatty acid molecules yield relatively less chemical energy compared to saturated fatty acids. This is because they are more oxidised (= less reduced) – they have less H atoms.  Generally; Oils contain unsaturated fatty acids while fats contain saturated fatty acids.  Because of the bends in the chains of unsaturated fatty acids… The molecules do not pack very tightly together Thus forms oils (liquid) straight chains in saturated fatty acids allow them to pack tightly. Thus forms fats (solid) Glycerol  Alcohols are a series of organic molecules which contain a hydroxyl group (-OH) attached to a carbon atom. Glycerol (C3H8O3) is an alcohol with three hydroxyl groups  Glycerol CH2OH-CHOH- CH2OH  Esterification A reaction between an acid and an alcohol (= esterification) produces a chemical known as an ester. Loading…  An ester bond (or ester linkage)is formed in the reaction between the carboxyl group (-COOH) of a fatty acid and one of the hydroxyl groups (- OH) of glycerol.  Condensation reaction glycero 3 fatty acids Triglycerid 3 water l e (Fat or oil)  Condensation reaction R R R R R R glycero 3 fatty acids Triglycerid 3 water l e (Fat or oil)  A glyceride is an ester formed by a fatty acid combining with the alcohol glycerol. A condensation reaction occurs between a molecule of glycerol and one, two or three molecules of fatty acids.  Triglycerides are the most common lipids in cells. In mammals, lipids are mostly in the form of triglycerides. As reservoirs of stored fatty energy  Lipids can be hydrolysed, with the help of an enzyme can lipase, into glycerol and fatty acids.  Triglycerides are the most common lipids in cells. In mammals, lipids are mostly in the form of triglycerides. As reservoirs of stored fatty energy Can be hydrolysed, with the help of lipase, into glycerol and fatty acids. Role of lipids (triglycerides)  Triglycerides have a higher proportion of hydrogen than either carbohydrates or protein.  Used as energy storage Store 3X more energy than carbohydrates of the same mass. Many plants and animals convert surplus food into oils or fat as an energy store o Insulation and buoyancy  Which of the following is not true about glycerides? A. Triglycerides have a higher proportion of hydrogen and carbon than either carbohydrates or protein.. Glycerides are synthesised by a condensation reaction between a molecule of glycerol and one, two or three molecules of fatty acids.. Unsaturated glycerides have a high content of double bonds and hence they have high melting points. D. In mammals, lipids are mostly in the form of triglycerides.. Glycerides are located in various organs and particularly in adipose tissue.  PHOPHOLIPIDS A phosphate group (PO4 3- ) in place of one of the fatty acid chains.  Phosphate group makes phospholipids polar molecules, negatively charged phosphate end is hydrophilic. An amphipathic  molecule FUNCTIONS Effective as emulsifying agents. They are the components of bile and lipoproteins  Constituents of cell membranes. They anchor proteins within the cell membranes  Phospholipids are integral part of cell membranes  GLYCOLIPIDS Lipids that contain a sugar residue. The basic structure: mono- or oligosaccharide group attached (acetylated or alkylated) to A sphingolipid or A glyceride  These make up the classes of glycosphingolipids and glycoglycerolipids,  Glycolipids are widely distributed in tissue including the brain  interact and bind to the lipid-bilayer through the hydrophobic nature of the lipid tail They are anchored it to the surface of the plasma membrane WAXES “esters” formed from long-alcohols and long- chain carboxylic acids.  Waxes are found almost everywhere. solid at ambient temperature. plastic in nature bend under pressure in the absence of heat. generally insoluble in water.  Functions of lipids (waxes) o Waterproofing/Protecting plant leaves from drying  STEROIDS Steroids are hydrophobic in nature Many are involved in the regulation of metabolism. Examples include testosterone, estrogen, cholesterol and vitamin D.  All steroids are made from cholesterol (C27H45OH) The hydroxyl group makes cholesterol an alcohol and is responsible for its slight solubility in water.  Has a hydrocarbon tail, a body of four ring structures and a hydroxyl group. The ring parts of the molecule together with its hydrocarbon chain are nonpolar. Thus it is an amphipathic molecule.  Cholesterol travels in the blood through lipoproteins such as low density lipoproteins (LDL) high density lipoproteins (HDL).  Functions of lipids (steroids) Cholesterol is a structural component of cell membranes and helps to maintain its structural integrity. o Chemical communication, as hormones  Which of the following does not match a lipid with its function? A. Oils – waterproofing feathers and fur. B. Steroid hormones – energy storage. C. Cholesterol – maintaining membrane fluidity. D. Wax – protective coating on leaves.