lipids, classifications, and sorces.pptx

lipids, classification and sources

1. Lipids, classification and sources Dr. Vinod Kumar Patil Assistant Professor Department of Food and Nutrition Faculty of Sciences Khaja Bandanawaz University Kalaburagi

2. Lipids consist of fats, oils, hormones, and certain components of membranes that are grouped together because of their hydrophobic interactions. The lipids are essential constituents of the diet because of their high energy value.   These are also essential for the fat-soluble vitamins and the essential fatty acids found with the fat of the natural foodstuffs. Fats combined with  proteins  (lipoproteins) are essential constituents of the cell membranes and  mitochondria  of the cell. Lipids occur naturally in living beings like plants, animals, and microorganisms that form various components like cell membranes, hormones, and energy storage molecules. Lipids exist in either liquid or non-crystalline solids at room temperatures and are colorless, odorless, and tasteless. These are composed of fatty acids and glycerol.

3. Fatty acids are organic molecules that are long-chained carboxylic acids with 4-36 carbon atoms. The hydrocarbon chains are either saturated or unsaturated, depending on the bonds between the carbon atoms. If all the carbon-carbon bonds are single, the acid is saturated; if one or more carbon-carbon double bonds are present, the acid is unsaturated. Naturally occurring fatty acids are mostly unbranched, and these occur in three main classes of lipids; triglycerides, phospholipids, and cholesteryl esters. Fatty acids are not found in the free state but remain associated with alcohol to form triglycerides. Fatty acids are stored as an energy reserve (fat) through an ester linkage to glycerol to form triglycerides.

4. 1. Hydrolysis of triglycerols Triglycerols like any other esters react with water to form their carboxylic acid and alcohol– a process known as hydrolysis. 2. Saponification: Triacylglycerols may be hydrolyzed by several procedures, the most common of which utilizes alkali or enzymes called lipa­ses. Alkaline hydrolysis is termed saponifica­tion because one of the products of the hydrolysis is a soap, generally sodium or potassium salts of fatty acids. 3. Hydrogenation The carbon-carbon double bonds in unsaturated fatty acids can be hydrogenated by reacting with hydrogen to produce saturated fatty acids. 4. Halogenation Unsaturated fatty acids, whether they are free or combined as esters in fats and oils, react with halogens by addition at the double bond(s). The reaction results in the decolorization of the halogen solu­tion. 5. Rancidity: The term rancid is applied to any fat or oil that develops a disagreeable odor. Hydrolysis and oxidation reactions are responsible for causing rancidity. Oxidative rancidity occurs in triacylglycerols containing unsaturated fatty acids.

5. Lipids are important fats that serve different roles in the human body. The three main types of lipids are triacylglycerols (also known as triglycerides), phospholipids, and sterols. 1)  Triglycerides  make up more than 95 percent of lipids in the diet and are commonly found in fried foods, butter, milk, cheese, and some meats. Naturally occurring triacylglycerols are found in many foods, including avocados, olives, corn, and nuts. We commonly call the triglycerides in our food “fats” and “oils.” Fats are lipids that are solid at room temperature, whereas oils are liquid. 2)  Phospholipids  make up only about 2 percent of dietary lipids. They are water-soluble and are found in both plants and animals. Phospholipids are crucial for building the protective barrier, or membrane, around your body’s cells. In fact, phospholipids are synthesized in the body to form cell and organelle membranes. In blood and body fluids, phospholipids form structures in which fat is enclosed and transported throughout the bloodstream. 3)  Sterols  are the least common type of lipid. Cholesterol is perhaps the best well-known sterol. Though cholesterol has a notorious reputation, the body gets only a small amount of its cholesterol through food—the body produces most of it. Cholesterol is an important component of the cell membrane and is required to synthesize sex hormones, vitamin D, and bile salts.

6. Fats satisfy  hunger  (the  need  to eat) because they’re slower to be digested and absorbed than other macronutrients. Dietary fat thus contributes to  satiety —the feeling of being satisfied or full. When fatty foods are swallowed, the body responds by enabling the processes controlling digestion to slow the movement of food along the digestive tract, giving fats more time to be digested and absorbed and promoting an overall sense of fullness.  Lipids perform many functions within the body: 1) Store Energy –  When we take in more energy than we need, the body stores it as adipose tissue (fatty tissue, which we call fat). Carbohydrates and lipids provide most of the energy required by the human body. As discussed in the Carbohydrates unit, glucose is stored in the body as glycogen. While glycogen provides a ready source of energy, it is quite bulky with heavy water content, so the body cannot store much of it for long. Fats, on the other hand, can serve as a larger and more long-term energy reserve. Fats pack together tightly without water and store far greater amounts of energy in a reduced space. A fat gram is densely concentrated with energy, containing more than double the amount of energy as a gram of carbohydrate.

7. 2) Regulate and Signal –  Lipids regulate the temperature of your body, keeping it steady, not too hot, and not too cold.  Lipids also help the body produce and regulate hormones for everything from appetite to the reproductive system to blood clotting.  Lipids are key to brain structure and function; the lipids form nerve cell membranes, insulate neurons (the cables that send messages throughout the body), and help send signals within the brain. 3) Insulate and Protect –  Our bodies are padded with fat, protecting us from everyday friction. The average body fat for a man is 18 to 24 percent and for a woman is 25 to 31 percent 1. Still, adipose  tissue can comprise a much larger percentage of bodyweight depending on the degree of obesity of the individual. Some of this fat is stored within the abdominal cavity, called  visceral fat,  and some are stored just underneath the skin, called  subcutaneous fat . Visceral fat protects vital organs—such as the heart, kidneys, and liver. 

8. Dietary lipids are primarily oils (liquid) and fats (solid).  Commonly consumed oils are canola, corn, olive, peanut, safflower, soy, and sunflower oil.  Foods rich in oils include salad dressing, olives, avocados, peanut butter, nuts, seeds, and some fish.  Fats are found in animal meat, dairy products, and cocoa butter. SATURATED AND UNSATURATED FATS Most oils are high in monounsaturated or polyunsaturated fat and low in saturated fat.  Monounsaturated fats help regulate blood cholesterol levels, thereby reducing the risk of heart disease and stroke. Both monounsaturated fats and polyunsaturated fats provide nutrition that is essential for normal cell development and healthy skin. Monounsaturated fat –  This type of fat is found in plant oils. Common sources are nuts (almonds, cashews, pecans, peanuts, and walnuts) and nut products, avocados, extra virgin olive oil, sesame oil, high oleic safflower oil, sunflower oil, and canola oil. Polyunsaturated fat –  This type of fat is found mainly in plant-based foods, oils, and fish. Common sources are nuts (walnuts, hazelnuts, pecans, almonds, and peanuts), soybean oil, corn oil, safflower oil, flaxseed oil, canola oil, and fish (trout, herring, and salmon). Saturated fat –  This fat is found in animal products, dairy products, palm and coconut oils, and cocoa butter. Limit these products to less than 10 percent of your overall dietary fat consumption. Saturated fat, which is found in meat, dairy products, and some plant oils, is associated with increased bloodstream cholesterol.  High cholesterol levels indicate that a person is at a major risk for disease, such as heart attack.  Avoid saturated fat, or at least consume in moderation.

9. Biosynthesis of fatty acids Initiation – the formation of free radicals Propagation – the free radical chain reactions Termination – the formation of non-radical products

10. 1 mol of ATP is split to AMP and 2P i −2 ATP 8 mol of acetyl-CoA formed (8 × 12 ATP) 96 ATP 7 mol of FADH 2  formed (7 × 2) 14 ATP 7 mol of NADH formed (7 × 3) 21 ATP Total 129 ATP

11. Deficiency is associated with impairment in growth and reproduction, increased BMR. EFA are predominantly present in vegetable oils and fish oils. At least 30 % of dietary fat should contain PUFA.

12. Factors affecting the development of lipid oxidation in foods Fatty acid compositions Oxygen and free radicals Pro-oxidants Antioxidants and additives Processing conditions of meat- Irradiation, cooking, grinding, mixing, packaging, etc Storage: Time and conditions

13. Metabolic defects The major classes of  lipoproteins  are chylomicrons,  very-low-density lipoproteins  (VLDL),  intermediate-density lipoproteins  (IDL),  low-density lipoproteins  (LDL), and  high-density lipoproteins  (HDL). Disorders that affect lipid  metabolism  may be caused by defects in the structural proteins of lipoprotein particles, in the cell receptors that recognize the various types of lipoproteins, or in the enzymes that break down fats. As a result of such defects, lipids may become deposited in the walls of blood  vessels , which can lead to  atherosclerosis  (a  disease  characterized by abnormal thickening and hardening of the walls of the arteries). Familial hypercholesterolemia is an autosomal dominant disease that is caused by the deficiency of the LDL receptor on the surface of cells in the liver and other organs. As a result, cholesterol is not moved into the cells. Under normal conditions, when enough cholesterol is present in the cell, feedback mechanisms signal enzymes to cease cholesterol synthesis.

14. During prolonged starvation, the metabolism of fats stored in adipose tissue is needed for energy production. After the glycogen stores have been depleted, both gluconeogenesis and the production of ketone bodies by liver fatty acid beta-oxidation (or β-oxidation) are essential for providing energy for the brain. Fatty acid oxidation disorders are relatively common and as a group may account for approximately 5 to 10 percent of cases of sudden infant death syndrome (SIDS). The disorders commonly manifest with hypoglycemia, liver disease, decreased muscle tone, and heart failure (cardiomyopathy). The mitochondrial respiratory chain consists of five multi-subunit protein complexes that produce the majority of energy driving cellular reactions. Dysfunction of the respiratory chain leads to decreased energy production and to an increase in the production of toxic reactive oxygen species. Lipid profile is a pattern of lipids in blood. It includes the levels of total cholesterol, high density lipoprotein (HDL) cholesterol, triglycerides and is calculated as very low density lipoproteins and cholesterol ratio.

15. Low density lipoprotein (LDL) High level lipids associate with heart disease Good level: below 200 mg/dl (low risk of heart disease) Border line: 240 mg/dl (higher at high risk) LDL: cholesterol from liver to blood then to organs. It has less protein content and contains more cholesterol. High LDL in blood associated with atherosclerosis, heart disease and myocardial infraction. High LDL in blood will deposit in blood artery and trigger clot formation.

16. High density lipoprotein (HDL) Its good cholesterol, carried from organs and blood to liver to get rid of it. Removes excess cholesterol from tissues High levels linked to reduce risk of heart and blood vessel disease (40-60 mg/dl.