Question

Mrs. Ruhala set up an experiment where she tested for the presence of monosaccharides in food. She took a cracker, and it tested negative for monosaccharides. Then she put the cracker in her mouth, chewed it for a few minutes, and then spit it out into a test tube. It now tested positive for monosaccharides.

What happened?

a
The physical action of chewing broke down the lipids in the cracker and producing a positive reaction.
b
Water in the saliva catalyzed the cracker proteins and broke them into monosaccharides.
c
Mrs. Ruhala is a magical being and ewww.
d
An enzyme in her mouth broke down the polysaccharides in the cracker into monosaccharides.

Answer 1

The correct answer is:

d. An enzyme in her mouth broke down the polysaccharides in the cracker into monosaccharides.

When Mrs. Ruhala chewed the cracker, the enzyme amylase in her saliva began to break down the carbohydrates (specifically, starches) in the cracker into simpler sugars, including monosaccharides. This is why the cracker tested negative for monosaccharides before chewing and tested positive afterward.