Question 12 - Science Practice Test for the ACT

Fatty acids are organic lipids that are found in many foods people eat, such as beef, milk and corn. These fats differ in their fatty acid composition and are considered to be either saturated or unsaturated fats. Saturated fats have no carbon double bonds, whereas unsaturated fats have one (monounsaturated) or more (polyunsaturated) carbon double bonds (Figure 1). Chemical compounds with double bonds assume different geometrical shapes depending upon the configuration of the double bond. Some examples of typical fatty acids are shown in Figure 2. Different shapes of a compound are called isomers. Unsaturated fatty acids can assume the cis or trans isomer. The cis isomer refers to when hydrogen atoms are on the same side of a carbon double bond, whereas the trans isomer refers to when hydrogen atoms are on opposite sides of a carbon double bond. Trans fatty acids are a major concern to consumers around the world as they may contribute to coronary heart disease by raising LDL cholesterol (i.e., bad cholesterol) levels and lowering HDL (i.e., good cholesterol) levels. Some trans fatty acids come from dairy and meat, but most come from hydrogenated vegetable and fish oils. Some people believe that unsaturated fats are healthier for you than saturated fats, however, it is best to limit your daily intake of all kinds of fats.

Amy is studying the properties of lipids in her biochemistry class and these lectures have sparked her interest in fatty acid content in common foods. For her final term project, she decided to run experiments in the lab to determine the saturated, monounsaturated and polyunsaturated fatty acid content in different foods that she often eats. Figures 3 and 4 show her results.