Our next investigation centered around amylase, an enzyme found in our saliva that breaks down carbohydrates, like starch, into simple sugars. As we've discussed in the past, just reading this fact, or having the teacher make the claim, is not enough evidence. We needed to test this hypothesis and use our own results to support the claim.
Because we're also learning about experimental design, I gave everyone a worksheet to help plan this investigation in advance. However, the way I set up the sections around independent variables and dependent variables was confusing! Please ask questions if you are not sure. You should be able to complete the beginning of the planning worksheet, up to deciding on what factors you will need to keep constant.
Most important was choosing the right focus question. Sometimes, the best way to do that is to change the claim from a statement to a question. My claim was:
"The enzyme amylase breaks down starch into simple sugars."
This is the claim we want to try to support with evidence. Before I continue, it's important for me to mention that we cannot completely prove a claim or hypothesis, we can only support it. We can always disprove or fail to support a claim or hypothesis, but if we were to say that we had proven a hypothesis, it is the same as saying that it is definitely, always, 100% true. We can't be sure of that! In science, a lot of our work is to find evidence to support our claims – claims which are often made to disprove or refute an existing claim. As we learn more and more about the way our universe works, we must be open to the idea that everything we know could be eventually proven inaccurate, incomplete, or just plain incorrect. It's an idea we'll come back to again and again!
In the meantime, we need to ask a focus question for our investigation. If we change my claim into a question, we get:
"Does the enzyme amylase break down starch into simple sugars?"
This seems like a good focus question for our investigation. For our next investigation, you will be asked to determine this question on your own.
One of the challenges of this lab was determining what samples we should test. We could just put amylase in a test tube with some cornstarch and see if it breaks it down into sugar. During the last investigation, we learned how to use Benedict's solution as an indicator for sugar. We could then test the sample after five minutes and see if sugar was present. Wouldn't that be enough evidence?
The fact that I've set up the investigation for three samples is probably a clue that it isn't. What I would like you to do is imagine a conversation you are having with someone who is very doubtful of the claim. They want you to support the claim with evidence. So, let me start this conversation for you, and I will be the doubtful person – the Skeptic. I am going to use Accountable Talk to press you to support your claim with evidence.
You: "The enzyme amylase breaks down starch into simple sugars."
Me: "Can you share your evidence for your claim?"
You: "I put amylase and cornstarch in a test tube, waited for five minutes,
then I tested for sugar using Benedict's solution as an indicator.
the result showed me that there is now sugar. So this supports the claim."
Me: "I am not sure whether that evidence is valid for your claim, because
how can you be sure there wasn't already sugar in the samples you used?"
This is something to consider while you're designing your samples to test. Is there a way you can answer these questions before they are asked? Can you provide reasoning that uses three samples to tell the whole story about how the claim is supported? We will revisit this after the investigation and work together to construct our reasoning.
One thing we did on the following day was view a video from YouTube of an x-ray of a person swallowing foods. You can find many of these videos by doing a search on YT for "x-ray swallowing" or "fluoroscope swallowing." The first result is probably the one I showed in class. Either way, it is important that you check the description of the videos to make sure that you are watching a healthy person swallowing... some of the videos are from patients with problems swallowing food. You might not be watching the normal function of swallowing if you watch one of these.
In the reading for Lesson 4, there is a good diagram of the swallowing process. One of the big questions we had coming into today's investigation had to do with how we can eat and breathe through the same tube. Now we know more about the answer to that question!
