Lipids can be described as hydrophobic molecules that are soluble in organic solvents (Berg, Stryer, & Tymoczko, 2010). Lipids are important because they are used to store energy, act as structural components for cell membranes, and play a significant role in signal-transduction pathways. There are several classes of lipids – fatty acids, triacylglycerols, phospholipids, glycolipids, and steroids.
Many people have heard about fatty acids, such as omega-3 and omega-6 fatty acids, or “essential fats”. But what does this mean, and why are people told to take these fatty acids? First, we should understand what makes up a fatty acid. Fatty acids are made up of hydrocarbons (i.e. a long chain of carbons that have hydrogens on them), and have a carboxylic acid group at the end of the chain. The fatty acids are in their ionized form at their physiological pH, meaning that the –COOH group in the fatty acid looks like -COO-. In other words, instead of carboxylic acid, it is in its carboxylate form. The reason why fatty acids are given names such as “omega-3” is due to the location of the double bond in the fatty acid structure; namely between carbon-3 and carbon-4 when counting from the carboxylate carbon.
Fatty acids make an excellent source of fuel because they provide more energy during a combustion reaction (Berg, Stryer, & Tymoczko, 2010). This is because the fats’ structure has a lower ratio of oxygen compared to carbohydrates, or a more reduced structure. It is said that omega-3 fatty acids are good for lowering the chances of getting cardiovascular disease (Dawkins, Johnson, Pace & Willian, 2013), and obtaining them through diet is necessary due to the body inability to make them.
Another fat that many people have heard of are trans-fats and how we should avoid it in our foods. What are trans-fats? Again, this refers to the structure of the fatty acid. Most fatty acids contain an even number of carbon atoms, where 16 and 18-carbon fatty acids are the most common (Berg, Stryer, & Tymoczko, 2010). Fatty acids have either a saturated chain or it can be unsaturated with several double bonds. In saturated fats, the molecules are able to stack on top of each other, making the fat easier to solidify (i.e. solidify in the organs). Since the unsaturated forms contain double bonds, the bonds can lay cis (same side) or trans (opposite sides) to each other. The cis-bonded molecules makes a “kink” in the fatty acid, thus making the molecules less likely to stack up (i.e. the fat would most likely be in a liquid form (Berg, Stryer, & Tymoczko, 2010). The trans-bonded molecules are more likely to solidify because the molecules are orientated in a way so that they are closer together. However, the only way trans-bonded molecules occur is by...