Fats & Oils Investigation. Fats and oils naturally occur in food, and play a vital role in human nutrition and a healthy diet. They are used to store energy in the human body, insulate various bodily tissues such as the stomach and liver, and transport f

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AS and A Level Science

“The role of fats and oils in our diets.”

Part A: Chemistry of fats and oils

Introduction and types of fats and oils

Fats and oils naturally occur in food, and play a vital role in human nutrition and a healthy diet. They are used to store energy in the human body, insulate various bodily tissues such as the stomach and liver, and transport fat-soluble vitamins in the bloodstream. The types of fats are differentiated through their molecular structure, and can be broken down into the following sub-categories: saturated fats, monounsaturated fats, polyunsaturated fats and trans fatty acids. (Ellis-Christensen, 2011) Each of these sub categories behave differently when consumed in the human body, with all four types consists of “fatty acids,” which are made up of the molecules carbon and hydrogen in myriad of compounds.

Structure and chemistry

Fats and oils are straight chained carboxylic acids, which feature the elements of carbon (C), hydrogen (H) and oxygen (O), and contain the functional carboxyl group (-COOH) on one end. Saturated fats are quite literally “saturated” with hydrogen molecules, occupying all the bonds that carbon can hold, therefore results in no double or triple bonds between the carbons. Since there are three hydroxyl groups in a glycerol molecule, three carboxylic acid molecules are attached to each glycerol, creating trigylcerides, or “tri-esters of glycerol.” (Anon, 2010) Monounsaturated fatty acids have substantially less hydrogen molecules than saturated fats, and this is due to the double bond present in its structure. The same goes for polyunsaturated fatty acids, which can contain more than one double bond. A fat that is mono-unsaturated has two fewer carbon-hydrogen bonds because it has one extra carbon-carbon bond called a double bond, thus one carbon-carbon double bond has less energy than two carbon-hydrogen bonds, and consequently a mono-unsaturated fat contains less energy than a saturated fat.  The more unsaturated the fat is poly-unsaturated, the less energy it contains. (BHC, 2011) 

Fat metabolism

When fats are placed in water, they exhibit hydrophobic properties, meaning they “clump” together in masses and thus reducing the amount of surface area exposed to the water. For the human body to digest this, bile, which is secreted by the liver and stored in the gall bladder, is a catalyst which helps to break down the fat. This process is similar to the way detergent dissolves greases and oils; it dissolves the masses of fat into tiny droplets. (Lab MedNews, 2010) Once this is process is completed, the fats then form molecules called triglycerides, which, as previously mentioned, is made up of a glycerol molecule and three fatty acids, which contain the functional group (-COOH). The triglycerides have to then be broken down into simpler molecules by lipase, an enzyme secreted by the pancreas and forms a compound called monoglyceride, which is similar in structure to triglyceride, with the difference that rather than three fatty acids attached, monoglyceride has only three. Once the body has broken the triglycerides down, they remain dissolved in the bile and further form small droplets called micelles. As they travel through the digestive system, they come into contact with cells that line the intestines, and are then absorbed into them through their cell membranes. When this process is completed, the human body then reassembles the products into triglycerides, the form of fat that is most commonly found in the human body. These compounds are tightly packed together with protein and cholesterol into particles called chylomicrons. The small intestinal cells then secrete the chylomicrons into the lymph vessels, which are located in the neck, underarms and groin, and are eventually passed into the bloodstream. Once the fats are in the bloodstream, the body is able to transport them to wherever they are needed, and later breaking them down for energy or storing them as fat is energy is not needed.

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Unsaturated fats are easier to metabolise due to the double-bond present in its structure, and this means that the hydrocarbon is able to undergo a series of reactions, one of which being the “addition” reaction. In order for a saturated fat to be metabolised, the body has to form an unsaturated fat, and from then break it down through the reactions of the double bond that is contained in the unsaturated fat. Saturated fat is seen as a “bad” fat because more energy is needed to break it down, whereas in unsaturated fats, much less energy is used to undergo ...

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Fats & Oils Investigation. Fats and oils naturally occur in food, and play a vital role in human nutrition and a healthy diet. They are used to store energy in the human body, insulate various bodily tissues such as the stomach and liver, and transport f
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