The textbook only mentions how fats are broken down in passing, and I wanted us to spend a little more time investigating what happens. Our resources are limited, but I was able to come up with a synthetic model for lipase that we used for this investigation.
Before I go any further: I wanted to quickly mention that in our investigations during this unit, we are only skimming the surface of what is actually happening in the digestive system in our bodies. I have mentioned this before, but maybe not on the blog... I see our middle school science classroom as sitting on the beach of a large lake – let's call it Lake Science. We're standing on the shore of the lake, skipping stones across the surface of the water. As we study the digestive system, we're skipping stones across the top. We get to investigate some of the basics, but we don't stay in one place long enough to go very deep. It's important to know that we're only visiting the top of Lake Science! We are, for example, studying three enzymes in digestion. But there are many, many more than just the three enzymes, just as there are many other types of sugars, many types of proteins, and so forth. For our skipping stones, we'll study just these basics. When you reach high school, you'll learn more of the details as you go deeper into the lake. College will take you even deeper!
Anyway, back to our investigation! From the book, we learned that there are many more digestive substances added to the mix when the food is released from the stomach to the first part of the small intestine, called the duodenum. These digestive juices come from several sources, including the gallbladder, the liver, and the pancreas. More details can be found in the Lesson 6 reading, but most of it is buried in the fiction story about the two aliens that shrink down into someone's body, and it drives me crazy that we're expected to use this as evidence. At least there's a good diagram of the organs found here! One important enzyme added when food reaches the duodenum is lipase. Our claim is that the enzyme lipase breaks down fat into fatty acids.
We took a small amount of oil and a small amount of water and added them to a plastic sample tube and capped it. We then gently mixed the contents and examined the results. We saw, as expected, that the oil and water do not mix. The oil breaks down into large droplets, but quickly reassemble and separate from the water, rising to the top. We then added three drops of a synthetic version of an enzyme called lipase, and mixed the tube again. This time, the oil droplets were smaller, and took longer to separate from the water. We used this as visual evidence that the lipase breaks down the fat droplets found in food into smaller droplets. In reality, the lipase breaks apart fats called triglycerides into fatty acids and another substance, which can sometimes be measured using pH as an indicator. For our purposes, though, this will serve as sufficient evidence to support our claim.
