The failed experiment
The last chapter in our Real Science 4 Kids Chemistry book was about Protein and DNA.
Proteins and DNA are polymers that are inside every living thing. Proteins are amino-acid polymers, and DNA chains are made of nucleic acids and sugars. Proteins do ALL of the work inside our cells. And they have a variety of jobs which include moving molecules, making new molecules, and cutting and assembling molecules.
DNA carries the genetic code, which is like a library of information telling the cells when to grow, when to divide, and what proteins to make.
Our experiment was to investigate the cutting action of proteins in our saliva (spit).
We already knew from past experiments that bread contains starch, and that you can prove it is there by touching the bread with iodine. The reddish iodine will turn black upon contact with starch.
Our experiment was supposed to show that digestion of starches begins in the mouth. Unchewed bread will turn black when exposed to the iodine because of the presence of starch. But the more you chew the bread, the less black the iodine will look. This was because the saliva has an enzyme, amylase, that breaks down the amylose (starch) in the bread. That is the “cutting action” of that protein at work.
The setup:
We have one piece of bread, iodine, a dropper, and 4 petri dishes.
The first petri dish has a piece of bread that has not been chewed. The second dish has a piece of bread that has been chewed for 30 seconds. The third was chewed for one minute, and the last was chewed for two minutes.
Our next step was to drop iodine on each sample to determine the amount of starch left in each bit of bread.
Unfortunately, the iodine turned black on each sample. We repeated this experiment twice because I thought GB had not chewed properly (how dumb is that?). So I tried it myself, chewing properly, of course. But we got the same results. The teacher’s manual assured that the black color would lessen with each chewing progression. Perhaps GB and I don’t have good cutting proteins….LOL!
I also determined that there is NO way that I could survive one of those eating challenges on shows like ‘Survivor’ or ‘Amazing Race’ because trying to chew that dumb piece of bread was causing me to severely gag……….. and it’s JUST bread…… Can you believe that?
Well, that ends our Chemistry course. I’m kind of on the fence about it. The experiments were fun, and we did learn a lot. But I think there actually needs to be more substance to the chapters. I was really glad that Theresa and Superboy were doing Chemistry, too. Because we got to see some different experiments using the same concepts that we were studying.
The next book in the set is Biology. And I think GB will really like it. But I’m going to take a short break from the book learning and try this instead. It’s called Journey North. With it, we will learn more about the Earth’s daily and seasonal cycles. It will incorporate Science, Geography, and Math. And using our new skills we hope to be able to find the ten mystery classes around the world based on their latitude and longitude, daily sun cycles, and seasonal information. I think this will be fun for GB and we are hoping to do it at the same time as Dana, from School for Us, down in Texas.
Anybody want to join us?
Oh, we did Journey North 2 yrs ago ( I think) and it was a LOT of fun!
Comment by
lapazfarm — December 18, 2007 @ 10:29 am
btw, I think that experiment was poorly designed. I don’t think that any amount of chewing will give the saliva enough time to break down enough of the starch to make a real difference in the iodine color. The classic experiment is to use a bit of saltine cracker and then chew it long enough so that you can TASTE the sugar forming (as the by-product of the breakdown of starches). But even then, you still will have a good bit of starch left.
You could try collecting a vial of saliva (gross, I know) and then adding a tiny bit of cornstarch. Take out a drop and test immediately, and then again after a few minutes and see if you can detect a color difference. I’m still not sure if this will work, but it should have a better chance than a chunk of bread.
Comment by
lapazfarm — December 18, 2007 @ 10:38 am
We plan to do Journey North too! At least, I need to find out what exactly we have to do and figure out how I’m supposed to do this and then we plan to do it. We’d love to join you and share notes or whatever… Need to get more info after the holidays…
Comment by Christine — December 18, 2007 @ 8:43 pm
Cool experiment. Judging from the pictures, you may want to try doing the test with smaller pieces of bread. The amount of work that salivary amylase can do is limited–most starches in the food we eat are broken down by pancreatic amylase that is secreted into the small intestine after swallowing the food. So, the larger a piece of bread, the more likely there is enough starch left to react with the Iodine, even after chewing it for awhile.
Another way to possibly increase the success of the experiment would be to stimulate the parotid gland (source of salivary amylase and bicarbonate, which keeps the mouth’s pH where it needs to be for salivary amylase to work best) before starting the experiment by chewing gum (sugar free probably would probably be best) for a few minutes.
Check out this reference:
http://books.google.com/books?id=CUAROKYFhcQC&pg=PA111&lpg=PA111&dq=most+carbohydrate+digested+by+pancreatic+amylase&source=web&ots=5iUB9FiId0&sig=W4fdri7cIHO_ooSZmrTgE4ukqx4
Happy Testing
-DocBish
Comment by DocBish — December 18, 2007 @ 8:49 pm
Love your experiments. Looks like lots of fun.
Comment by Martha — December 18, 2007 @ 10:17 pm
I’m glad DocBish has some ideas for you! And, it seems like you both learned SO much from this book and study. I’m very proud of you both!!!
Can’t wait to learn more about Journey North and dive in with you!
I’ll have to post about it on my blog, too, and maybe we can get a group together.
Comment by Dana — December 19, 2007 @ 9:18 am