Lipid Nutritional Biochemistry PDF

Chapter 3 Lipid nutritional biochemistry Lipids are organic compounds, containing carbon, hydrogen, and oxygen C, H, O and they are relatively essential for life insoluble in water (with exception), but soluble in fat solvents as ether, alcohol, benzene and chloroform. They are not polymers(not for...

Chapter 3 Lipid nutritional biochemistry Lipids are organic compounds, containing carbon, hydrogen, and oxygen C, H, O and they are relatively essential for life insoluble in water (with exception), but soluble in fat solvents as ether, alcohol, benzene and chloroform. They are not polymers(not formed of repeating units like polysaccharides). What are the functions of lipids? 1- They are efficient energy sources. 2- Serve as thermal insulators. 3- They enter in the cell membrane structure. 4- Steroid hormones synthesis 5- They important for absorption and digestion fat soluble vitamins(A,D,E,K). 40   4 types of lipids fats (triglycerides) Simple lipids  phospholipids  steroids  waxes I-Simple lipids -Oil---liquid at room temp -Fat---solid at room temp -They are ester of fatty acid + glycerol Triacylglycerol TAG Structure of Triacylglycerol (TAG) [Neutral fat] They are esters of: Glycerol (alcohol ) & 3 fatty acids Glycerol 41 Biological Functions of Lipids 1- Storage of energy 1- In the body, fats provide: high energy. Energy – 9 kcals/gm Supplies of body’s energy 2- Stored as adipose tissue 3- Insulation & protection for heat. Health Effects of Fats Excess fat intake contributes to many diseases including: 1. Obesity 2. Diabetes 3. Cancer 4. Heart disease Fatty Acids (Saturated and Unsaturated) fatty acids are obtained by the hydrolysis of neutral fats. Many different fatty acids occur naturally in foods. In their free form, the fatty acids have the configuration shown herewith. Structure of Fatty Acids They are not found free in nature but found as esterified forms. They are mono carboxylic (only one –COOH-) long chain organic acids, which is completely ionized in plasma. The non-polar hydrocarbon chain (tail) makes them water insoluble. 42 Classification of Fatty Acids Saturated fatty acids No Unsaturated fatty acids contain double bonds. a.Mono-enoic F.A =1 double bond double bonds e.g. oleic acid (18:1) (olive oil). e.g. palmitic acid (16). polyenoic F.A > one double bond stearic acid (18). Linoleic acid (18:2), 2 double bonds (sunflower and corn oils). Linolenic acid (18:3), 3 double bonds (canola, soy been oils). Arachidonic acid (20:4), 4 double bonds (formed from linoleic acid). 1-SATURATED FATS: 1- Do not contain any (No C=C )double bonds TAG with fatty acids whose side chains are referred to as saturated fats. 2- long, straight chain 3- most animal fats and butter 4- solid at room temperature 43  5- contributes to cardiovascular disease ( Consumption of saturated fats (C14 &C16 FAs) is strongly associated with high levels of total plasma cholesterol and LDL and an increased risk of coronary heart disease.. 6- The main sources of saturated fatty acids are dairy and meat products and some vegetable oils, such as coconut and palm oils. 2-UNSATURATED FATS UNSATURATED FATS 1-They are less harmful to the circulatory system than saturated fats. they are typically in liquid form At room temperature, Monounsaturated fatty acids: are generally derived from vegetables present in nuts and oils as olive, peanut, and canola oils. Polyunsaturated fatty acids: in fish and oils as corn and sunflower. Monounsaturated fats lower both total plasma cholesterol and LDL cholesterol, but increase HDLs. This may explain in part, the observation that Mediterranean cultures, with diets rich in olive oil (high in monounsaturated oleic acid), show a low incidence of CHD.. 4- At room temperature, they are typically in liquid form. Waxes  Solid at room temp  Insoluble in water  Function:  Protective covering for animals and plants  44   Examples:  Beeswax  Earwax  Cuticle of leaf (keeps water in) Phospholipids  Structure: 2 fatty acids chains + phosphate head  Fatty acid chains = non-polar = hydrophobic  Phosphate head = polar = hydrophilic “water loving”  Function: make up cell membranes (phospholipid bilayer) Lipoproteins: General term for all diseases of the heart and blood vessels Low density lipoproteins (LDL) transports cholesterol from liver through blood to the tissues (Bad cholesterol) LDL is positively associated with CVD High density lipoprotein (HDL) transports cholesterol from blood to the liver where it is metabolized (Good cholesterol) HDL is negatively associated with CVD Chylomicrons 45  VLDL – Very low density lipoprotein Each contains different kinds and amounts of lipids and proteins – The more lipid, the lower the density – The more protein, the higher the density. Chylomicrons meaning small particle), also known as ultra low-density lipoproteins (ULDL), are lipoprotein particles that consist of triglycerides phospholipids cholesterol and proteins They transport dietary lipids from the intestines to other locations in the body. ULDLs are one of the five major groups of lipoproteins (sorted by density) that enable fats and cholesterol to move within the water-based solution of the bloodstream.  LDL is positively associated with CVD  HDL is negatively associated with CVD  Cardiovascular disease (CVD) Cardio = heart, & Vascular = blood vessels General term for all diseases of the heart and blood vessels  Steroids Structure: 4 fused Carbon rings  Examples:  cholesterol – Function =control the fluidity of the cell membrane 46  hormones – Function = regulate processes in the body (such as pregnancy)  vitamins (A, D) – Function = supports metabolism and cell processes Dietary Recommendations In developed countries dietary fats provide 30 to 40 per cent of total energy intake. The WHO Expert committee on Prevention of Coronary Heart Disease has recommended only 20 to 30 per cent of total dietary energy to be provided by fats. 1. Limit total fat intake to