Download “Digestion Simulation” Experimental Question: How does physical

“Digestion Simulation”
Experimental Question: How does physical digestion facilitate the chemical digestion of food?
Physical Digestion
Most animals take in food in large pieces, and must physically reduce it to smaller fragments before it can be
attacked by digestive enzymes.
Large pieces of food can be broken down by mastication, churning, and emulsification. Mastication involves
biting, slicing and grinding with the teeth. Vertebrates have a wide array of dental specializations that suit the
diet of each species. Humans, however, have fairly generalized teeth that allow a varied diet. Chewing food
well can improve digestion substantially
Most of the work of physical digestion takes place by churning in the stomach. The stomach itself is designed to
create maximum turbulence as it contracts.
The combined action of all three layers, coordinated by rhythmic firing of the connecting nerves, causes the
stomach to agitate the food. This is the motion you feel when you get butterflies in your stomach. When this
agitation is combined with the chemical effects of acid in the stomach, fragments of food can be reduced to a
liquid suspension in less than an hour.
Chemical Digestion
Majority of our food can be categorized as carbohydrates, lipids (fats), or proteins. These groups are polymers
(long chains of repeating components) which can be broken down into smaller subunits. The process of
digestion is simply the breaking up of long chains of polymers so that they can be incorporated into the system.
This is done through the help of biological catalysts known as enzymes. Without these chemicals, our body
cannot absorb the large molecules of food.
Inside the stomach, where food is temporarily stored, that preliminary chemical digestion begins. Partially
digested food then goes to the small
intestine where much of the digestion and
absorption of nutrients occur. The
large intestine simply serves for
the further absorption of water.
To understand the process of
digestion better, we shall look at
the process for each type of food
– proteins, lipids or fats,
and carbohydrates.
Chemical digestion of proteins starts in the stomach. The stomach produces HCl which helps unravel the three
dimensional structure of a protein. Next, enzymes called Pepsin break down the proteins into their amino acid
subunits. The chemical digestion of protein continues with the breakdown of proteins by enzymes in the small
intestine.
The chemical digestion of lipids or fat digestion occurs only in the small intestine. Bile, which is produced by
the liver and stored gall bladder, emulsifies fat molecules into smaller molecules. Then they are hydrolyzed
into fatty acids and glycerol by the pancreatic lipase another digestive enzyme, and are then absorbed in the
intestine.
Starches are first broken down into simple sugars by amylase, an enzyme found in the saliva of your mouth.
When starch enters the stomach the amylase does not function because of the high level of acidity in the
stomach, unlike the mouth. So carbohydrate digestion does not progress in the stomach. Next, the pancreas
releases amylase into the small intestine which continues to break down starch. Now the starch can be absorbed
through the villi of the small intestine for transport to our cells. The cells will use most of the sugar we ingest to
release energy by cellular respiration.
Hypothesis: In your own words make a prediction for the experimental question. Support your prediction with
reasoning or details from the reading above.
Procedure
1. Obtain to Alka-Seltzer tablets which will represent food in our digestion simulation.
2. Crush one tablet into a small powder and leave the other table whole.
3. Drop the whole tablet into 50 mL of water and record the total amount of time required for the tablet to be
completely dissolved. The tablet is dissolved when it stops releasing gas, or fizzing.
4. Drop the crushed tablet into 50 mL of water and record the total amount of time required for the tablet to be
completely dissolved. You may have to stir the solution so all the powder comes into contact with the water.
Data
Construct a data table and graph that shows the time required for each form (whole and powdered) of the AlkaSeltzer to dissolve. Enter your data into the class table, and calculate the mean, median and mode.
Conclusions
1. Describe how physical digestion helps with the chemical digestion of food. Support your answer with data
from your experiment.
2. Evaluate the simulation we used to true digestion. Which parts of the simulation are accurate or inaccurate?
Explain which parts of the simulation represent physical digestion, chemical digestion, enzymes and food.
3. Describe how and where proteins, carbohydrates and lipids are broken down in the digestive system.
4. Do the enzymes in the digestive system perform dehydration synthesis or hydrolysis? Explain your
reasoning.
5. Compare and contrast mechanical and chemical digestion. Include examples of physical and chemical
digestion in your answer.