Presentation on theme: "Lipids Prof. Dr. Suat Erdoğan EBN School of Medicine"— Presentation transcript:
1Lipids Prof. Dr. Suat Erdoğan EBN School of Medicine Medical Biochemistry DepartmentOctober 2013
2Outline Description of lipids Function of lipids Fatty acids TriglyceridesCholesterolSteroids
3LipidsLipids (or fats) are a heterogeneous class of naturally occurring organic compounds classified together on the basis of common solubility properties.They are insoluble in water, but soluble in nonpolar solvents, including ether, chloroform, benzene and acetone.
4Major lipidsLipids may be polar or nonpolar (amphipatic). Polar lipids have limited solubility in water because they are amphipatic.Major lipids includetriacylglycerols, phosphodiacylglycerols, sphingolipids, glycolipids, lipid-soluble vitamins, and prostaglandinscholesterol, steroid hormones, and bile acids
5Properties of Lipids Do not readily dissolve in water Fats are solid at room temperatureOils are liquid at room temperatureTriglycerides are the main form of lipids in food and body (storage)Energy dense (9 kcal/g)
6Functions of Lipids Provide energy Efficient storage of energy InsulationProtectionTransport fat-soluble vitaminsMembrane componentsSatietyFlavor and mouth feel
7Provide and storage of energy In the body, fat serves as an efficient source of energy (ATP), both directly and potentially when stored in adipose tissue.
8Fat cells in the bodyThe fat is stored in living cells, called fat cells (= adipocyte). Adipocytes makes adipose tissue.
9IsolationFats serves as a thermal insulator in the subcutaneous tissues and around certain organs, andNonpolar lipids act as electrical insulators allowing rapid propagation of depolarization waves along myelinated nerves.
11ProtectionBelow the dermis lies a layer of fat that helps insulate the body from heat and cold, provides protective padding, and serves as an energy storage area.
12Transport fat-soluble vitamins Combinations of fat and protein (lipoproteins) are important cellular constituents, occurring both in the cell membrane and in the mitochondria within the cytoplasm, and serving also as the means of transporting lipids in the blood.
13Membrane componentsMembrane lipids are a group of compounds (structurally similar to fats and oils) which form the double-layered surface of all cells. The three major classes of membrane lipids are phospholipids, glycolipids, and cholesterol.
14SatietyLipids suppress food intake when present in the small intestine of both humans and animals.
15Flavor and mouth feelFats have little taste, but contribute mouth feel and carry odorants.Fat has a major influence on the sensory perception of food products. Fats enhance the taste and acceptability of foods, and lipid components largely determine the texture, flavor and aroma of foods.
16Lipids are classified as simple and complex 1. Simple lipids: esters of fatty acids with various alcohols.Fats: esters of fatty acids with glycerol. A fat in the liquid state is known as oil.Waxes2. Complex lipids: esters of fatty acids containing groups in addition to an alcohol and fatty acids.PhospholipidsGlycolipidsOther complex lipids
17Fatty acidsFatty acids occur mainly as esters in natural fats and oils but do occur in the unesterified form as free fatty acids (FFA), a transport form found in the plasma.The fatty acid chain may be saturated (containing no double bonds) or unsaturated (containing one or more double bonds). Unsaturated fatty acids may be further subdivided as follows:Monoansaturated acids, containing one double bond (oleic acid).Polyunsaturated acids containing two or more double bonds (linoleic acid, arachidonic acid).
21Saturated fatty acid structure H H H H H H H H H H H H H H H H H OH-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OHH H H H H H H H H H H H H H H H Homega end alpha enddegree of saturationStearic acid: C18H38O2
25Unsaturated fatty acids Palmitoleic acid (16:1)Oleic acid (18:1)Linoleic acid (18:2)-Linolenic acid (18:3)-Linolenic acid (18:3)Arachidonic acid (20:4)16:1 mean: a fatty acid contains 16C and 1 double bond in the structureColored in red demonstrates essential fatty acids.
26Deficiency of essential fatty acids Essential fatty acid deficiency results in dermatitis.Clinical signs of essential fatty acid deficiency include a dry scaly rash, decreased growth in infants and children, increased susceptibility to infection and poor wound healing.
28Monounsaturated Fatty Acid Structure H H H H H H H H H H H H H H H OH-C--C--C--C--C--C--C--C--C=C--C--C--C--C--C--C--C--C-OHH H H H H H H H H H H H H H H H Homega end alpha endOne double bond
29Polyunsaturated Fatty Acid Structure H H H H H H H H H H H H H OH-C--C--C--C--C--C=C--C--C=C--C--C--C--C--C--C--C--C-OHH H H H H H H H H H H H H H H H Homega end alpha end> 2 double bonds
30Essential Fatty Acid- Omega-6 (linoleic acid) H H H H H H H H H H H H H OH-C--C--C--C-- C--C =C--C--C=C--C--C--C--C--C--C--C--C-OHH H H H H H H H H H H H H H H H Homega end alpha end1st double bond is located on the 6th carbon from the omega end
31Omega-6 (linoleic) fatty acid Found in vegetable oilsOnly need ~ 1 tablespoon a dayArachidonic acid can be made from omega-6Metabolized to form eicosanoids
32Essential Fatty Acid- Omega-3 (linolenic acid) H H H H H H H H H H H H H H H H H OH-C--C--C=C--C--C =C--C--C=C--C--C--C--C--C--C--C--C-OHH H H H H H H H H H Homega end alpha end1st double bond is located on the 3rd carbon from the omega end
33Omega-3 (linolenic) fatty acid Primarily from fish oilAlso found in canola or soybean oilMetabolized to form eicosanoidsRecommend intake of ~2 servings of fish per week.
34Essential Fatty Acids Must be eaten Body can only make double bonds after the 9th carbon from the omega end.Needed for immune function, vision, cell membrane, and production of hormone-like compounds.
35Signs and Symptoms of Essential Fatty Acids Deficiency Itchy skinDiarrheaInfectionsRetarded growth and wound healingAnemia
45PhospholipidsPhospholipids are a class of lipids that are a major component of all cell membranes as they can form lipid bilayers. Phospholipids contain a diglyceride, a phosphate group and choline.Built on a glycerol backboneHas at least one fatty acid replaced with phosphorus containing compoundFound in bodySynthesized by the body as needed
47Functions of Phospholipids Makes up cell membraneEicosanoid synthesisEmulsifierBile acidsLecithins
48Emulsifier Hydrophilic end (attracts water) Hydrophobic end (attracts lipid)
49EmulsificationEmulsification refers to the process of dispersing a substance such as oil in an emulsion. It also refers to the process of converting two or more immiscible liquids into an emulsion. During this process, large fat globules are broken down into smaller, evenly distributed particles.
50GlycolipidsGlycolipids are lipids with a carbohydrate attached to an -OH of the lipid. Their role is to provide energy and also serve as markers for cellular recognition.
51SterolsSterols, also known as steroid alcohols, are a subgroup of the steroids and an important class of organic molecules. They occur naturally in plants and animals, with the most familiar type of animal sterol being cholesterol. Cholesterol is vital to animal cell membrane structure and function and a precursor to fat-soluble vitamins and steroid hormones.A multi-ringed structureDo not have a glycerol backboneDo not readily dissolve in water
52Functions of Cholesterol Essential component of cell membraneProduced by the liverFound only in animal productsForms important hormonesEstrogen, testosterone, vitamin DPrecursor to bile acids
54Androgens Androgens - male sex hormones synthesized in the testes responsible for the development of male secondary sex characteristics
55Estrogens Estrogens - female sex hormones synthesized in the ovaries responsible for the development of female secondary sex characteristics and control of the menstrual cycle
56Eicosanoids A group of hormone-like compounds Regulates blood pressure, childbirth, clotting, immune responses, inflammatory responses, & stomach secretionsBy-pass the blood stream and work in the area of origin
57Eicosanoids Have Different Effects Omega-6 eicosanoids; archidonic acidincrease blood clottingincrease inflammatory responsesOmega-3 eicosanoidsdecrease blood clottingreduce heart attackexcess may cause hemorrhagic strokeEicosanoid has different effect on different tissues.
59ProstaglandinsProstanoids are a subclass of eicosanoids consisting of the prostaglandins (mediators of inflammatory and anaphylactic reactions), the thromboxanes (mediators of vasoconstriction), and the prostacyclins (active in the resolution phase of inflammation.)
60ProstaglandinsProstaglandins are not stored in tissues as such, but are synthesized from membrane-bound 20-carbon polyunsaturated fatty acids (arachidonic acid) in response to specific physiological triggers
61ProstaglandinsResearch on the involvement of PGs in reproductive physiology has produced several clinically useful derivatives15-Methyl-PGF2 is used as a therapeutic abortifacient
62Leukotrienes Leukotrienes: derived from arachidonic acid found in white blood cells (leukocytes)an important property is constriction of smooth muscles, especially in the lungs
63Thromboxanes derived from arachidonic acid contain a four-membered cyclic ether within a six-membered ringinduce platelet aggregation and smooth muscle contraction
64What are lipoproteins?A lipoprotein is a biochemical assembly that contains both proteins and lipids. The lipids or their derivatives may be covalently or non-covalently bound to the proteins. Examples include the high density (HDL) and low density (LDL) lipoproteins which enable fats to be carried in the blood stream, the transmembrane proteins of the mitochondrion and the chloroplast, and bacterial lipoproteins function of lipoprotein particles is to transport water-insoluble lipids (fats) and cholesterol around the body in the blood.
69SummaryA knowledge of lipid biochemistry is important in understanding many current biomedical areas of interest e.g. obesity, diabetes, atherosclerosis, and the role of various polyunsaturated fatty acids in nutrition and health.
70Content ReviewWhat are some important functions of the essential fatty acids?How are saturated fatty acids different from unsaturated fatty acids?What is esterification?What are the main functions of lipid in the body?What are emulsifiers?