Case Study

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE

Fat Facts: Comparing the Structure and Function of Lipids

by Ling Chen and Lalitha S. Jayant Science Department Borough of Manhattan Community College / City University of New York

This case study focuses on the structure and function of different fat molecules, such as fatty acid, triacylglycerol, glycerophospholipid, HDL, and LDL cholesterols. The story also compares the structures and melting points of the paired fatty acids, the saturated with unsaturated, monounsaturated with polyunsaturated, cis- with trans-isomers. The structure of omega-3 polyunsaturated fatty acid is also explained. • It’s noon on Mother’s Day. Dolly, a busy high school senior, is in the kitchen gathering all the utensils and ingredients needed to make a Mediterranean salad in honor of her mother, a single parent and part-time college student. Life hasn’t been easy, but mother and daughter are making the best of it and are very close. Lucy, the mother, is majoring in chemistry and takes every opportunity to teach Dolly what she has learned in school. As a result, Dolly has developed a love for science, aced all of her AP science classes, and plans to pursue a career in science. You are about to witness one of the many chemistry lessons that happens often in their kitchen. Dolly: Mom, where’s the olive oil? I need it to make a salad dressing quick. Mom: It’s in the fridge, honey. Dolly: Got it, but it looks thick and cloudy. I can’t pour it out. What happened? Why is it in the refrigerator? Mom: I keep all my oils in the refrigerator so they stay away from heat and sun light. It slows down the oxidation processes. Dolly: What’s an oxidation process? You mean to prevent oils from becoming stale? Mom: Yep. Oils react with oxygen and undergo a process called oxidation, which makes them rancid, or stale, as you called it. They smell awful after they become rancid. Dolly: But I need the oil now; should I use canola oil instead? Mom: Calm...