Lipids Lecture Slides PDF

Faculty of Applied Health Sciences Department of Health Sciences Lipids  Faculty of Applied Health Sciences Department of Health Sciences Learning goals 1. Compare the chemical makeup and physical properties of...

Faculty of Applied Health Sciences Department of Health Sciences Lipids  Faculty of Applied Health Sciences Department of Health Sciences Learning goals 1. Compare the chemical makeup and physical properties of saturated fats, monounsaturated fats, polyunsaturated fats, phospholipids, and sterols. 2. Explain lipid digestion, absorption, and transport. 3. Identify the different lipoproteins and the roles they play. 4. Understand Health Canada’s recommendations as it relates to total lipids, n3 lipids, n6 lipids, saturated fats, trans fat, and cholesterol and identify which lipids support health and which may impair it. 2  Lipids Faculty of Applied Health Sciences Department of Health Sciences The Functions of Fats In the Body Energy stores. Fats are the body's chief form of stored energy. Muscle fuel. Fats provide much of the energy to fuel muscular work. Padding. Fat pads inside the body cavity protect the internal organs from shock. Insulation. Fats insulate against temperature extremes by forming a fat layer under the skin. Cell membranes. Fats form the major material of cell membranes. Raw materials. Fats are converted to other compounds, such as hormones, bile, and vitamin D, as needed. 3  Faculty of Applied Health Sciences Department of Health Sciences Lipids Base unit of lipids is fatty acid Fatty acids: chain of carbons with Acetic acid hydrogen atoms along the chain and at one end (methyl end) and carboxyl group (-COOH) at the other end (acid end) Classification 1. Chain length 2. Level of saturation 4  Faculty of Applied Health Sciences Department of Health Sciences Chain length Length of carbon chain – most common fatty acid carbon chain lengths are with 14-24 carbons Short and medium are digested and transported more quickly 5 Stearic acid, 18-carbon fatty acid; 18:0  Faculty of Applied Health Sciences Department of Health Sciences Level of saturation Saturation – refers to the number of H atoms the carbons in the fatty acid are holding – max number of H, without carbon-carbon double bonds = saturated fatty acid (SFA) – SFA do not have double bonds in between the long hydrocarbon chain Stearic acid e.g. in coconut oil, a saturated fatty acid, 18-carbon fatty acid; 18:0 6  Faculty of Applied Health Sciences Department of Health Sciences Level of saturation (cont’) Unsaturation – addition of a double bond in between the long hydrocarbon chain, where 2 hydrogen atoms are missing – 1 double bond, monounsaturated fatty acid (MUFA) Oleic acid e.g. in olive oil, monounsaturated fatty acid, 18 carbon-fatty acid; 18:1 7  Faculty of Applied Health Sciences Department of Health Sciences Level of saturation (cont’) Unsaturation (cont’) – more than 1 double bond (more than 4 hydrogen atoms are missing), polyunsaturated fatty acid (PUFA) (e.g. linoleic acid in plant seeds and oils) Linoleic acid e.g. in sunflower oil, polyunsaturated fatty acid, 18 carbon-fatty acid, 18:2 8  Faculty of Applied Health Sciences Department of Health Sciences Level of saturation (cont’) Location of double bond – count from methyl end - N is where we found the first double bound from the methyl end – first double bond (n or omega) Linoleic acid e.g. in sunflower oil, n-6 or omega-6 fatty acid, 18:2(n-6) Linolenic acid e.g. in fish oil, n-3 or omega-3 fatty acid, 18:3(n-3) 9  Faculty of Applied Health Sciences Department of Health Sciences Essential fatty acids Two fatty acids cannot be synthesized in the body and must be obtained in the diet – Linoleic acid (LA, n-6 or omega 6) (found in seeds of plants and their oils, e.g. corn oil, sunflower oil etc) – -linolenic acid (ALA, n-3 or omega 3) (found primarily in flaxseed and flaxseed oil); EPA and DHA made from ALA and also found primarily in fatty fish and fish oils (e.g. salmon and salmon oil) NEED TO HAVE THESE ON THE DIET AS WE CAN NOT YSNTHEISIS THESE OILS WITHIN THE BODY 10  Faculty of Applied Health Sciences Department of Health Sciences Lipids Subclasses of lipids found in food and in human body: – triglycerides (fats and oils) – phospholipids – sterols (e.g. cholesterol) 11  Faculty of Applied Health Sciences Department of Health Sciences Triglycerides One of the main classes of lipids Chief form of fat in foods: 95% of all fats consumed in our diet Major storage form of fat in the body They are composed of – Three fatty acid molecules – One glycerol molecule Glycerol is a 3-carbon alcohol that is the backbone of a triglyceride 12  Faculty of Applied Health Sciences Department of Health Sciences Triglycerides Shape (chemistry) of fatty acids influences triglycerides The shape of a triglyceride is determined by the saturation of the carbon chains and by the type of double bond – Saturated fatty acids can be packed tightly together and are solid at room temperature (e.g. animal fats, tropical oils, butter) – Unsaturated fatty acids do not stack together well and are liquid at room temperature (e.g. plant oils) 13  Faculty of Applied Health Sciences Department of Health Sciences Know these examples Coconut oil (tropical oils) and animal products (e.g. butter) are high in saturated fatty acids Some vegetable oils (e.g. olive oil and canola oil) are high in monounsaturated fatty acids Most vegetable oils (e.g. safflower, sunflower and corn oil) are high in omega-6 (n-6) polyunsaturated fatty acids Flaxseed oil and fish oil (e.g. salmon) are high in omega-3 (n-3) polyunsaturated fatty acids 14  Faculty of Applied Health Sciences Department of Health Sciences Trans-fatty acids Hydrogenation: The addition of hydrogen atoms to monounsaturated or polyunsaturated fatty acids – converts liquid fats (oils) into a more solid form – used to create margarine from plant oil – often creates trans fatty acids 15 Faculty of Applied Health Sciences Department of Health Sciences Trans-fatty acids 16  Faculty of Applied Health Sciences Department of Health Sciences Trans-fatty acids (cont’) Naturally occurring – Conjugated Linoleic Acid (CLA) – found in beef and milk – may have health benefits (ex. weight loss) 17  Faculty of Applied Health Sciences Department of Health Sciences Lipids Subclasses of lipids found in food and in human body: – triglycerides (fats and oils) – phospholipids – sterols (e.g. cholesterol) 18  Faculty of Applied Health Sciences Department of Health Sciences Phospholipids Major component of cellular membranes – soluble in water, hydrophilic (head group) – soluble in lipid, hydrophobic (fatty acid tails) 19  Faculty of Applied Health Sciences Department of Health Sciences Phospholipids Phospholipids and sterols make up only five percent of dietary lipids Lecithin is a common phospholipid (know) - consists of glycerol with two fatty acids, a phosphate group, and a molecule of choline - used by food industry as emulsifier in foods such as margarine, chocolate etc - found for example in eggs, liver, soybeans, peanuts 20  Faculty of Applied Health Sciences Department of Health Sciences Lipids Subclasses of lipids found in food and in human body: – triglycerides (fats and oils) – phospholipids – sterols (e.g. cholesterol) 21  Faculty of Applied Health Sciences Department of Health Sciences Sterols Lipids containing multiple rings of carbon atoms – Examples: cholesterol, Vitamin D, sex hormones Many functions – emulsify fat (cholesterol in bile) – chemical messenger (testosterone, cortisol) – bone metabolism (vitamin D) 22  Faculty of Applied Health Sciences Department of Health Sciences Sterols Most sterols (e.g. cholesterol) are manufactured in our bodies and therefore are not essential components of our diet Cholesterol synthesized in the liver - Derived from carbohydrate, protein and fat - Found in cell membranes - Provides structural and metabolic functions Sterols found in plant and animal food sources 23  Faculty of Applied Health Sciences Department of Health Sciences Sterols Plant sterols found naturally in fruits and vegetables, nuts, seeds and oils, legumes and in fortified foods e.g. margarine, orange juice, yogurts etc look like cholesterol, thus can help block absorption of dietary cholesterol 2g/day can significantly improve blood cholesterol (e.g. 5 tsp Becel) Fortification is means added to the 24 produce  Faculty of Applied Health Sciences Department of Health Sciences Digestion - Lipids Fats are not digested and absorbed easily because they are insoluble in water. Limited digestion of fats occurs in the watery environments of the mouth or stomach. Most of the digestion of fats occurs in the small intestine. Note: for further info about digestion, absorption and transport of lipids look in subsections 2.2., 2.3, 2.4 in chapter 2 of your textbook/eBook 25  Faculty of Applied Health Sciences Department of Health Sciences Digestion - Lipids Mouth and salivary glands – melt hard fats – lingual lipase secreted from sublingual salivary gland: slight hydrolysis for most fats Stomach – churning action mixes fat with water and acid – gastric lipase: access and hydrolyses a small amount of fat 26  Faculty of Applied Health Sciences Department of Health Sciences Digestion - Lipids Small intestine – bile emulsifies fat (bile release from gallbladder triggered by Cholecystokinin CCK) – pancreatic and intestinal lipase breakdown emulsified fat (e.g. triglycerides into glycerol and fatty acids) Large intestine: Some fat and cholesterol, trapped in fiber, exit in feces 27  Faculty of Applied Health Sciences Department of Health Sciences Absorption - Lipids Enterocyte absorbs digestive products – cholesterol – free fatty acids – monoacylglyceride or monoglyceride (glycerol and fatty acid) Assistance of micelle Once in enterocyte, micelle is disassembled 28  Faculty of Applied Health Sciences Department of Health Sciences Absorption - Lipids Absorbed products treated differently – medium and short-chain fatty acids absorbed directly into the blood – solubility increased with albumin (protein) 29  Faculty of Applied Health Sciences Department of Health Sciences Absorption - Lipids Phospholipids, cholesterol, and resynthesized triglycerides repackaged with protein into chylomicrons (lipoprotein) in endoplasmic reticulum in enterocyte 30  Faculty of Applied Health Sciences Department of Health Sciences Need to know the difference between the differing lipids transpo Transport - Lipids Short- and medium-chain fatty acids move through the enterocyte and enter circulation through the capillaries They are transported by the protein albumin and they will be carried to the liver by the portal vein, like monosaccharides and amino acids Lipoprotein generated from digestion/absorption is a chylomicron 31  Faculty of Applied Health Sciences Department of Health Sciences Transport - Lipids Chylomicrons are too large to fit through the pores in the capillaries and they are transported through the lymphatic system 32  Faculty of Applied Health Sciences Department of Health Sciences Transport - Lipids Lipids always bundled with proteins for transport Lipoproteins – 4 different types (size and density; density varies according to proportion of lipids and proteins they carry) chylomicrons very-low-density lipoproteins (VLDL) low-density lipoproteins (LDL) high-density lipoproteins (HDL) 33 Faculty of Applied Health Sciences Department of Health Sciences Transport - Lipids Chylomicrons: the lipoproteins that transport lipids from the intestinal cells into the body. The cells of the body remove the lipids they need from the chylomicrons, leaving chylomicron remnants to be picked up by the liver cells. 34 Faculty of Applied Health Sciences Transport - Lipids Department of Health Sciences VLDL: the type of lipoproteins made primarily by liver cells to transport lipids to adipose and muscle tissue; composed primarily by triglycerides. 35 Faculty of Applied Health Sciences Department of Health Sciences Transport - Lipids LDL: the type of lipoproteins derived from VLDL as cells remove triglycerides from them. LDL carry cholesterol and triglycerides from the liver to the cells of the body (peripheral 36 Faculty of Applied Health Sciences Department of Health Sciences Transport - Lipids HDL: the type of lipoproteins that transport cholesterol back to the liver from peripheral cells; composed primarily of protein. 37  Faculty of Applied Health Sciences Department of Health Sciences Storage - Lipids Adipose tissue – triglycerides – efficient storage – virtually unlimited store 38  Faculty of Applied Health Sciences Department of Health Sciences Total lipids Provide flavor and texture Contribute to satiety DRI: 20%-35% of daily caloric intake Important source of energy (9 kcal/g) Diet low in saturated fat, trans-fat, and cholesterol 39  Faculty of Applied Health Sciences Department of Health Sciences NEED TO KNOW HOW TO DO THIS Total lipids Assuming 250 kcal come from protein, does a daily dietary intake of 344 g of CHO and 110 g of lipids meet Health Canada’s recommendations? Need to convert g to kcal – 344 g X 4 kcal/g = 1376 kcal CHO – 110 g X 9 kcal/g = 990 kcal lipids Compare kcal of CHO and lipid to total kcal – 1376 kcal CHO + 990 kcal lipids + 250 kcal protein = 2616 total kcal – 1376 kcal CHO / 2616 total kcal = 53% (within the CHO recommendations of 45%-65%) – 990 kcal lipids / 2616 total kcal = 38% (above the lipids recommendations of 20%-35%) 40  Faculty of Applied Health Sciences Department of Health Sciences n-6 fatty acids Essential fatty acid (linoleic acid) DRI: 5%-10% of daily caloric intake (11-22 g in 2000 kcal diet) 41  Faculty of Applied Health Sciences Department of Health Sciences n-3 fatty acids Essential fatty acid (-linolenic acid) along with DHA and EPA DRI: 0.6%-1.2% of total daily caloric intake (2.2 g in 2000 kcal diet) 42  Faculty of Applied Health Sciences Department of Health Sciences n-3 fatty acids Polyunsaturated fatty acids of omega- 3 family – Potent protectors against heart disease EPA and DHA mechanisms to protect heart health – Lower blood triglycerides – Prevent blood clots and irregular heartbeats – Lower blood pressure – Defend against inflammation 43  Faculty of Applied Health Sciences Department of Health Sciences Limit saturated fatty acids Keep to