Fat and oil are the same things. Fat is solid at room temperature and oil is liquid at room temperature. So what exactly is fat?
Fat is a subcategory of lipids - molecules that are not that soluble in water. There are two main parts of fats - glycerol backbone and fatty acid. Fat (and therefore oil) is made up of carbon, hydrogen and oxygen. The molecular structure of the fatty acid determines whether it is fat or oil.
The Building Blocks of Fat and Oils
Before talking about the difference between fats and oils, it is necessary to know how fats and soils are made up.
The backbone of fat is known as glycerol. The glycerol is a compound made up of three carbons bonded with hydrogen atoms and hydroxide. Here is a picture of the structure of glycerol -
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When Glycerol Meets Fatty Acid
Fatty acids are not fats per se. The magic happens when Glycerol meets fatty acids. Just like Glycerol has OH compound, the fatty acid has HO compound. OH is negatively charged, while HO Is positively charged. So there is a strong attraction between them. As a result, the OH compound of glycerol gets bonded to the H of HO from the fatty acid. The Oxygen of the HO compound gets separated and gets attached to the carbon atom of the glycerol. This results in the formation of fats.
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The Hydrogen atom of the HO cation at the left-hand side of the fatty acid gets attached to the OH anion at the right side of the glycerol. When glycerol gets connected with the fatty acid, the combination is known as glyceride.
Mono, Di and Triglyceride
As you can see from the diagram of glycerol, it has three levels of carbon-hydrogen molecules. When the fatty acid gets attached to the first level only, the combination is known as Mono-glyceride. If the fatty acid molecule gets attached to the two levels of the carbon-hydrogen bond, the combination is known as Di-glyceride. And if there are three fatty acid molecules connected to all three levels of the glycerol backbone, it is known as a triglyceride.
While Monoglyceride and Triglyceride are technically fats, they are known as emulsifiers. When we talk about fats, we generally mean triglyceride.
Now that you know what fat actually is, let us show you how fats and oils are different from each other.
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You know that fats have fatty acid chains. When the fat has fatty acid chains where the carbon atoms have single bonds, it is called saturated fat. Why saturated? Since there are single bonds and no double bonds, there are enough hydrogen atoms in it. In other words, this fat is saturated with hydrogen atoms. Hence it is called saturated fat. The presence of too many hydrogen atoms results in too strong intermolecular attraction in the fats. Hence the molecular structure of fats remains robust and stable. This makes the fats remain solid at room temperature.
But Why Exactly Saturated Fats are Unhealthy?
We all know from televisions, books and newspapers that saturated fat is unhealthy. But as far as chemistry is concerned, what exactly is there in the saturated fat that makes it so unhealthy? The answer lies in the previous point. As said, saturated fats are robust and solid. In the body, too, this fat remains solid and stable. It becomes very difficult for the body to break the molecular chain and make it liquid. As result overtime, with too much intake of saturated fat, the fats keep on getting collected in the body without being broken. As a result, the veins and arteries get blocked.
The Story of Unsaturated Fat
In an unsaturated fat, there is one or more double bond(s). As a result of this double bond, the amount of hydrogen in the fatty acid chain gets reduced. This reduction of hydrogen results in the fatty acid chain being weak and unstable. Hence, it is easily breakable. This makes unsaturated fats healthy as it cannot get accumulated in the body.
There are Two Types of Unsaturated Fats:
Monounsaturated Fats - Having only one double bond.
Polyunsaturated Fats - Having more than one double bond.
Omega - 3, 6 & 9
The end of the fatty acid having CH3 compound is known as the methyl end. If there is a double bond after three carbons counting from the end, the fat is known as Omega-3. If there is a double bond after 6 or 9 carbons - counting from the end - then the fat will be known as Omega 6 and 9 respectively. These Omega fats are extremely important to our health. Our body cannot generate these fats in a good manner. Hence we need these fats from external food sources.
A Few Things about Trans Fat
In most unsaturated fatty acids, the functional groups of the carbons are on the same side. These are called Cis Fats. There is a process called Hydrogenation that can add hydrogen atoms to the unsaturated fats to break the double bond and make it single. This makes the unsaturated fat turn into saturated Trans fat.
We all now know that Trans fats are bad for health. However, there are many food companies that use the word ‘hydrogenated fat’ to avoid mentioning Trans fat. You must be careful about this evil tactic of the companies.
Because of the ill effects of some of the form fats (mainly saturated fats), fat as a whole has gained a bad reputation. There is a very interesting Ted-Ed video on YouTube. It says that olive oil is 100% fat while the pancake mix is only 11% fat. Yet olive oil is considered healthy and the pancake isn’t. The answer lies in the types of fat that these two food products contain. It is, therefore, necessary to know about the differences between different types of fats.
1. What are Fats?
Ans. Fat is a type of lipids - molecules that are hydrophobic. There are two main parts of fats - glycerol backbone and fatty acid. Fat is made up of carbon, hydrogen and oxygen. The molecular structure of the fatty acid determines whether it is fat or oil.
2. What are Oils?
Ans. Oils are just the liquid version of fats. Fats remain solid at room temperature. But oils remain liquid at room temperature.
3. Why do Fats Remain Solid at Room Temperature?
Ans. Fats or saturated fats are made up of single-bonded carbon atoms. There is enough place for the hydrogen atoms to be there. Hence, fats are saturated with hydrogen. The greater number of hydrogens results in strong molecular bonds. The carbon atoms do not get broken easily. So it remains solid.
4. Why do Oils Remain as a Liquid?
Ans. Oils or unsaturated fats are made up of double-bonded carbon atoms. The extra bond fills some places of the hydrogen. As a result, there are fewer hydrogen atoms and less strong intermolecular forces. Furthermore, the carbon atoms in the unsaturated fats do not form a straight chain - the chain gets tweaked. As a result of these two things, the fatty acid chain is not that robust or strong. Hence oil or unsaturated fats remain in the liquid form at room temperature.
5. What are the Two Parts of Fats?
Ans. Fats are made up of glycerol backbone and fatty acid chains. The OH from the glycerol gets attached to the Hydrogen atom of the HO of the fatty acid. The left out oxygen atom gets attached to the carbon of the glycerol.