CSCP402 ASSIGNMENT 2018
Fats or lipids are classified into four groups triglycerides, phospholipids, steroids and prostaglandins (Patton & Thibodeau, 2016 p.58). Triglycerides are the most common and provide the most energy for the body. They are made up of a glycerol molecule and three fatty acids (Pattern & Thibodeau, 2016 p.58). The glycerol and fatty acids combine when the H from the glycerol combines with the OH of the fatty acid making H2O and leaving the O from the glycerol to form a bond with the C of the fatty acid as seen in Figure 1. The glycerol molecule is always the same in every triglyceride but the chemical properties of the triglyceride are decided by the type of fatty acid it attached to (Whitney, Rolfes, Crowe, Cameron-Smith & Walsh, 2014 p.126).
Figure 1. Formation of a triglyceride (Whitney et al., 2014 p. 126).
Phospholipids are another type of lipid and they are made up of a glycerol molecule, two fatty acids and a third chemical structure that includes phosphorus and nitrogen as seen in Figure 2 (Patton & Thibodeau, 2016, pp. 59-60). One end of the phospholipid has the phosphorus group so that end will be polar therefore hydrophilic or soluble in water. The opposite end with the two fatty acids is nonpolar or hydrophobic not soluble in water. This enables the phospholipid to live in 2 chemical conditions, water at one end and lipid at the other. They are an important part of the cell membrane because they form bilayers where the fatty ends line up facing each other and the polar heads are facing outside in the water (Patton 2016, pp. 59-60).
Figure 2. Stucture of a Phospholipid showing Polar and Nonpolar ends (Patton, 2016, p. 60).
Steroids are another lipid used throughout the body in physiological and anatomical roles (Paton, 2016, p. 60). They are made up of four carbon rings called the steroid nucleus and a functional group see Figure 3. They differ depending on the various functional groups that are attached. Cholesterol is a very important steroid that is found in the plasma membrane that surrounds every cell in the body.
Figure 3. Structure of a Steroid (Patton, 2016, p. 60).
Prostaglandins are another type they are made up of a 5 carbon ring attached to a 20-carbon unsaturated fatty acid see Figure 4 (Patton, 2016, p. 60). Commonly called tissue hormones they are regulators in the body.
Figure 4. Structure of a Prostaglandin (Patton, 2016, p. 60).
Fats and oils are triglycerides and they differ because of their chemical structure (“Human Nutrition,” 2018, Fats and Oils, para. 2). Fats are lipids that are solid at room temperature and this is because they are saturated fats. Saturated fats have fatty acids which have no double carbon bonds, butter and lard are saturated fats. Oils are lipids that are liquid at room temperature this is because they are unsaturated fats. Unsaturated fats have a fatty acid that has one or more double carbon bonds, corn and sunflower oils are unsaturated fats (“Human Nutrition,” 2018, Fats and Oils, para. 2).
Fats/lipids are nonpolar because of their chemical structure. They have low numbers of electronegative oxygen atoms so very few polar covalent bonds thus making them nonpolar and hydrophobic (Tortora & Derrickson, 2014, p. 45). As blood is made up of almost 55% plasma (“Blood,” 2018, Blood components section, para. 1) which is 90% water (“Blood,” 2018, Plasma section, para. 1) and water is polar because of its oxygen atoms electronegativity fats are insoluble in blood (“Water,” 2018, Structure of water section, para. 4). The body needs fats but has to break them down so they can be absorbed into the bloodstream. The process starts in the mouth where some hard fats melt when they reach body temperature and an enzyme in salvia, lingual lipase is released which can hydrolysis a bond in a triglyceride forming a diglyceride (Whitney, Rolfes, Crowe, Cameron-Smith & Walsh, 2014, pp. 132-135) . This very effective in infants but only has a small effect in adults. Once in the stomach the contracting of the stomach muscles break up the fat solids into smaller particles and an enzyme in the stomach gastric lipase can hydrolysis some of fat. The small intestine is where most of the fat is digested. When fat enters the small intestine a hormone cholecystokinin is released and this tells the gall bladder to release bile from its stores. The bile acids join with amino acids allowing the bile to be both hydrophobic at the sterol end and hydrophilic at the amino acid end. This allows the bile to act as an emulsifier which pulls the fat molecules into the watery fluid where the lipase enzymes from the pancreas and small intestine hydrolysis the fats. They break down triglycerides into fatty acids and glycerol or monoglycerides. The glycerol and fatty acids are easily absorbed into the intestinal cells then into the blood. The monoglycerides and long chain fatty acids need to merge with bile and form micelles. Micelles are molecules of bile with a monoglyceride or long chain fatty acid inside. They are soluble in the watery digestive fluid and can then be transported to the intestinal cells where the monoglyceride or long chain fatty acid portion of the micelle then diffuses into the intestinal cells. Once inside they form new triglycerides which are then packed with protein into chylomicrons the transport vehicles to move into the lymphatic system. They go through the lymphatic system to enter the blood at the thoracic duct. Once in the blood they are carried around the body for storage or use (Whitney et al., 2014, pp. 132-135).
The structure of the hydrogen carbon bonds in a fatty acid determines whether a fat is saturated or unsaturated (“Saturated fat,” 2018, para. 1). In a saturated fat the fatty acid has no double carbon bonds hence all the carbons are bonded to a hydrogen therefore fully hydrogenated or saturated in hydrogen. This makes the molecule stable and the carbon hydrogen bonds are harder to break which is why saturated fats are solid at room temperature (“Saturated fat,” 2018, para. 1).
Unsaturated fats are so called because they are not saturated in hydrogen bonds they will have at least one double or triple carbon bond (“Unsaturated fat,” 2018, para 1). Some can have up to 6 double bonds within the fatty acid. The carbon atoms are arranged in straight lines and the first double bond generally occurs between the ninth and tenth carbons from the terminal (-COOH) group (“Fat,”2018, Chemical composition of fats, para. 1-2). The more double or triple bonds in the fatty acid the less saturated the fat is and the weaker the structure and easier to break down hence unsaturated fats are generally liquids at room temperature eg oils (“Unsaturated fat,” 2018, para. 1).
Unsaturated fats are divided into two types, monounsaturated and polyunsaturated fats (“Unsaturated fat,” 2018, para. 4). Monounsaturated fats only have one carbon double bond per molecule, olive and peanut oil are examples. Polyunsaturated fats have more than one carbon double bond, fish oil and soy beans are polyunsaturated fats (“Unsaturated fat,” 2018, para. 4).
Fats are a great source of energy and are found in our foods, and some are good for human health while others are bad. Unsaturated fats, monounsaturated and polyunsaturated are good fats as they can lower bad cholesterol (LDL) in the blood which can reduce the risk of strokes and heart disease. They also deliver nutrients to the body which help maintain cells and function in the body for example omega-6 and omega-3 fatty acids which the body can not produce itself. Whereas saturated fats are bad fats and can cause many health problems. They can increase the levels of bad cholesterol (LDL) while lowering the good cholesterol (LDL). Dyslipidemia is when there is a rise in the level of lipids in the blood this can occur when there is too much saturated fat consumed. Fatty plaque on the inner linings of arteries narrowing the arteries causing blood clots and then heart attacks and strokes can be another result of saturated fats. Trans fats which are chemically modified fats are also bad. They have gone through the process of hydrogenation, adding hydrogen to a vegetable oil. Thus making them a semisolid fat and a more hydrogen saturated fat hence they now have similar negative outcomes to a saturated fat.