Fall SAVY 2016 (Day 3) – Intro to Macromolecules
We began Saturday’s class by working together to formulate a working definition of a macromolecule—a large molecule, consisting of many types of atoms, that is composed of monomers (repeating groups of atoms) put together. We moved from here to discuss our first category of macromolecule: carbohydrates. We learned that all carbohydrates are types of sugars (or saccharides) but that they differ in the number of sugar monomers present in each type. The students generated a great list of different foods that they consume that have carbohydrates. Some of the items on their list taste sweet—like fruit and candy—because they contain simple carbohydrates, such as glucose (a monosaccharide) and sucrose (a disaccharide). Others don’t taste sweet initially—like bread and pasta—because they contain complex carbohydrates, such as starch (a polysaccharide), that the body eventually breaks down to glucose to use as fuel. In light of this information, we had an interesting conversation about which types of carbohydrates might be best to eat in the context of physical activity. Ask your child which food he/she thinks a long-distance swimmer should consume a couple of hours prior to her race. Also discuss what someone might eat if he was exhausted at the end of a long run and needed a snack to “refuel” or boost his energy relatively quickly.
After talking through some basic food examples of each of the different types of carbohydrates, I provided the students with a list of foods and asked them to predict which ones had monosaccharides, disaccharides, and/or polysaccharides (mainly focusing on starch in this context). I then showed them how scientists can test for each of these types of sugars. The first test allows analysis of a sample for monosaccharides (and some disaccharides); it employs a reagent called “Benedict’s solution,” which, when added to a liquid test sample with slight heating, turns from blue to green/yellow/orange in the presence of mono- (and some di-) saccharides. We discussed that even if this test was negative, that did not guarantee that a sample food didn’t have any carbohydrates at all. Thus we performed a second test that employed iodine as an indicator for starch (a polysaccharide); iodine turns from a reddish-brown to a purplish-black color in the presence of starch. Ask your student if any of their results surprised them or if they noticed any trends about the types of foods that had simple versus complex carbohydrates.
We had so much fun with this lab that we ran out of time for a thorough post-lab discussion! Therefore, next time we will review our carbohydrate lab results before moving forward to discuss our next category of macromolecule—lipids (fats).