UNIT 5: Structure and Function of Organisms, Part 2
Page 194 S
e 100
Sheets 200 Pages Wide Ruled
9 3/4 x 7 1/2 in. 24.7 x 19.0 cm
Eat a Cracker
1. Y our teacher will give you two unsalted crackers.
2. Chew the crackers in your mouth for 2 minutes without swallowing.
3. Record your observations, including the initial taste of the crackers and
their taste after 2 minutes.
Why do we
chew our food before swallowing? We
chew food to break it
into smaller pieces and increase the surface area of the food so it can
break down faster. We
also chew food in order to swallow it easier.
Materials Materials
For teacher
For student groups
Petri dish or
portion cups with
fresh (not
Learning Goal
Identify physical and chemical changes in matter in the digestive system.
Teacher Instruction
Instruct students to chew the crackers without swallowing for 2 minutes.
Students should notice that the crackers become sweeter. This is due to the
release of an enzyme in the saliva that breaks down carbohydrates into glucose,
a simple sugar.
Teacher Note
Teacher Note
Many meat tenderizers use enzymes from plants.
Bromelain, the
enzyme in pineapple, and papain, the enzyme in papaya, break
down proteins.
Other fruits such as kiwi and figs also contain
enzymes that break down proteins.
Gelatin is made from protein.
Proteins are broken down into amino acids. This represents a
chemical change.
Canned pineapple slices will not work
because the canning
process destroys the enzyme in pineapples.
Materials Materials
For each student
2 unsalted
timer or access
to clock
Lesson 1: Physical and Chemical Changes in Digestion
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