Lab 2 –

Digestion

in the

Mouth

Tahoma Jr. High8th Grade ScienceMaple Valley, WA

Today’s Lab is to use the basic tests we learned to do for sugar and starch to confirm if the enzyme “amylase”

(present in your saliva) will break downstarches (complex sugars)into basic simple sugars.

The starch we’re using is called: amylose(in chemistry chemical names ending in “-ose” are sugars)

Enzymes end in “-ase” – so amylase should break apart amylose – simple! Science isn’t “that” hard !!

(you just have to learn the words first)

Notice starch is just a bunch of sugars bonded together like a train

SetupHere’s what needs to go into each cup to test if the enzyme

amylase actually breaks down starches into sugars

TEST FOOD TYPE

Benedict’s(sugar?)

Cup #1

starch

Cup #2

DWamylase

Cup #3

starchamylase

Lugol’s(starch?)

Cup #5

starch

Cup #6

DWamylase

Cup #7

starchAmylase

Now, make a prediction of what you think the results should be for each cup(put a + or – in the lower right corner of each cup’s boxand what color should appear AFTER you do the tests)

Record the start time when amylase was added

(need at least 30 mins for it to work)__________

NEXT SLIDE IS RESULTS

if you want to do your own version of this lab, go home and chew on a piece of bread or a unsalted

cracker for an extra long time (let the enzymes work on the starches) and swirl it around the tip of your tongue where your “sweet” taste buds are… see if there’s a sweet flavor that appears.

ResultsAfter doing the tests, here’s what results should have appeared.

TEST FOOD TYPE

Benedict’s(sugar)

Cup #1

starch

Cup #2

DWamylase

Cup #3

starchamylase

Lugol’s(starch)

Cup #5

starch

Cup #6

DWamylase

Cup #7

starchamylase

Starch alone in Cups 1 and 5 are tests to make sure each indicator chemical is working properly.

DW in Cups 2 and 6 are controls to make sure amylase does not react with the indicator chemicals by itself.

So, if amylase worked to break down the starch into sugar,Benedict’s would be positive.

Not all the starch was converted to sugar yet

Why did you get a positive starch test here if amylase breaks starch down into sugar?

may get “false positive” here – too much heat destroying enzyme??

…correct since the starch + amylase gave a positive result for sugar (the starch was broken down). Starch with amylase still had some starch in it (not all the starch was broken down yet) – starch was positive in a starch test.

Why did amylase and distilled water give a positive result?

I wonder if we could do this test on other enzymes that break down proteins?

end show