Lipids can be categorised into four main groups, phospholipids, prostaglandins, steroids and triglycerides (also called fats) (Patton and Thibodeau, 2016, p. 58) All Triglycerides are made up of fatty acids and glycerol. The glycerol in each fat molecule remains the same, and three carbon chain fatty acids join to it. An example of a triglyceride can be seen in Figure 1.
Figure 1. Formation of triglyceride (Patton & Thibodeau, 2016, p. 58).
Here the process of dehydration if forming a triglyceride with glycerol and the three molecules of the fatty acid named caproic acid which has a chain of six carbons (Patton & Thibodeau, 2016, p. 58).
Phospholipids are comparable to triglycerides, although instead of the same trio of fatty acids, one of them is replaced by a phosphate molecule which then attaches to a compound containing nitrogen, attached to the opposite end of the glycerol to the two fatty acids. (Patton & Thibodeau, 2016, p. 58). This can be seen in Figure 2.
Figure 2 ().
Steroids are big molecules consisting of four carbon rings (nucleus of the steroid) that are attached to each other, along with a different type of functional group for each different type of steroid. Steroids all have broadly different roles and functions as to why the functional group attached to the four rings varies (Patton & Thibodeau, 2016, p. 60). Examples of steroids can be seen in Figure 3.
Figure 3 ().
Prostaglandins are also named tissue hormones. These are a type of fat which are made up of a fatty acid consisting of 20 unsaturated carbons, five of which form a carbon ring. An example of a prostaglandin in which there are 16 types, can be seen in Figure 4 (Patton & Thibodeau, 2016, p. 60).
Figure 4 ().
Most oils and fats are made up of triglycerides (“Human Nutition,” 2018, Fats and Oils section, para. 2). Triglycerides contain a glycerol molecule with fatty acids in a group of three attached. The difference between fats and oils depends on whether the fatty acids are saturated or unsaturated. A saturated molecule in room temperature will be formed as a solid. This means that the fatty acid does not contain any double bonds. Oils are liquids at room temperature due to the fatty acids in the molecule being unsaturated. This means that the fatty acids contain double bonds. To conclude, fats are normally solid and oils are normally liquids. Examples of fats are lards and butter. Examples of oils are corn oil and sunflower oil (“Human Nutition,” 2018, Fats and Oils section, para. 2).
Over 90% of plasma in the blood is water (“Blood,” 2018, Plasma section, para.1). Water is made up of one oxygen and two hydrogen atoms (“Water,” 2018, Structure of Water section, para. 1). Water is a polar molecule due to the oxygen atom being negatively charged, therefore having more electronegativity than the positively charged hydrogen atoms (“Water,” 2018, Structure of Water section, para. 4). Lipids are insoluble in water, meaning it cannot dissolve. This is due to the molecules sharing electrons equally, no part of the lipid molecule is partially charged, therefore lipids are normally non-polar (Patton and Thibodeau, 2016, p. 58). A term used to describe lipids is hydrophobic. Therefore only very small lipid molecules are soluble in watery blood plasma. Lipids require the aid of a protein molecule in which is hydrophilic in order to be able to be dissolved in blood plasma. Once a protein has coated a lipid it is then called a lipoprotein. (Tortora & Derrickson, 2014, p. 45). The body finds it difficult to digest lipids. As fats are a hydrophobic substance, they do not digest in the bodies hydrophilic enzymes. The body requires lipids to be broken down into smaller molecules so the body is able to absorb and also use (Whitney, Rady Rolfes, Crowe, Cameron-Smith, & Walsh, 2014, p. 132). Inside the mouth is the beginning of fat digestion, body temperature begins to melt the fat. Lingual lipase is an enzyme released by the tongues salivary gland to aid in the digestion of fat, mainly in infants. Stomach churning then grinds larger fat particles into smaller fat particles (or droplets) This gives the enzyme gastric lipase better access to begin digestion. The hormone cholecystokinin is released when the fat reaches the small intestine. This hormone instructs the gall bladder to dispense stored bile produced by the liver using cholesterol. Within bile acids, the amino acid attracts the water and the sterol part (from cholesterol) attracts the fat. The fat is able to be drawn into surrounding water by the biles structure allowing it to perform like an emulsifier. The fat particles are no longer attracted to each other giving lipase the opportunity to completely digest the lipids. The lipase is mostly produced by the pancreas, less by the intestines. The action of the the enzymes on the triglyceride molecules is called hydrolysis. Two or sometimes three of the fatty acids are broken off from the glycerol. If one fatty acid remains it is called monoglyceride. Hydrolyisis also removes the fatty acids from phospholipids to be better absorbed. Small and medium sized fatty acid chains and glycerol are able to be transported to the blood stream directly through cells of the intestinal walls.
There is a difference in structure between saturated and unsaturated fats. They are both types of fatty acids which are made of long chains of carbons in even numbers with hydrogens attached to each of the carbons. A carboxyl group attaches on the very end of the carbon chain (-COOH) (“Fatty Acid,” 2018, para. 1). Whether the fat molecules carbons are completely saturated with hydrogens determines which category the are placed into. Saturated fat molecules are an organic molecule in which the hydrogen atoms saturate each carbon. This also means that each carbon in the chain is connected by single bonds only (Sebley & Cymet, 2018, para. 1). Unsaturated fats contain carbon atoms that are not saturated with hydrogen atoms. This means that two or more of the carbons in the chain are connected with a double or triple bond. Unsaturated fats can also be divided into two types; monounsaturated and polyunsaturated. Monounsaturated fat only contains one double bond between two carbon atoms within each molecule. Polyunsaturated fat contains two or more double bonds between carbon atoms within each molecule (Aenlle, 2018, para 1-3). The double bonds between carbons in unsaturated fats can be a maximum of six within the molecule. The more double bonds it has, the lower the melting point becomes. It is usually between the ninth carbon and tenth carbon away from the carboxyl group in the chain that the first double bond or unsaturated carbon can be found (Fat, 2018, para. 3).
Unsaturated fats such as monounsaturated and also polyunsaturated fats can be considered a healthy fat. Consuming foods which contain unsaturated fats such as salmon and soy beans can have a positive effect on human health. These types of fat are capable of helping reduce levels of bad cholesterol and lower risk of health issues with the heart. Skin and body cells require these types of fatty acids to remain healthy and continue developing (Aenlle, 2018, para 2-3). Consumption of food including polyunsaturated fats is the only way of the body obtaining these vital fatty acids. The body requires these fats for important body functions (American Heart Association, 2017, para. 2-3). Levels of bad cholesterol in the blood can be lowered by the consumption of monounsaturated fats. Therefore, the risk of strokes and heart disease can be lowered. The bodies cells also require these essential nutrients for growth and repair (American Heart Association, 2017, para. 2). Saturated fats can be considered an unhealthy fat for the body. At room temperature these molecules are usually in solid form. Consumption of saturated fats can be blamed for the rise in bad cholesterol in the body and can also be the reason for dyslipidaemia and atherosclerosis. Examples of foods that contain saturated fats include dairy products and meat (Sebley & Cymet, 2018, para. 1-3). Atherosclerosis is a condition caused by an accumulation of fat in the arteries linings. This caused for arteries to become narrow which may then cause a stroke or heart attack from the clogging of the arteries (Aldridge, 2011, para. 1).