BIOL 2404 A&P Basics Digestive Exercises Dr. Weis
Experiment I: Energy Transfer
A. Absorption of Heat by Water: Heat Storage
This experiment will help you become familiar with the absorption of
heat, the temperature change, and a calorie measurement.
Measure 250 ml of room temperature water
(~1 cup + 1 Tablespoon) into a sauce pan. Record
the initial temperature using a (candy or chemistry) thermometer.
Heat the water on your stove using a medium setting until it has reached 60°C.
Turn off the heat and record the final temperature.
Answer the following questions
1) How many grams of water did you add to the saucepan?
2) Calculate the amount of heat absorbed by the water.
Helpful conversion factors:
°F= (°C) x (9/5) + 32
Density = mass / volume Water has a density of 1.0
Specific heat of water is 1 calorie per gram per degree.
B. Heat of Solution of a Salt
When salts dissolve in water there is a breakdown of the crystal
structure and an interaction (hydration) of water molecules with
ions of the salt. In this experiment you will measure the heat affect
associated with the solution of a particular salt in water. Remember
that many physical process as well as chemical reactions can be
exothermic or endothermic.
Measure 10g of regular table salt using a food scale. Fill half a small Styrofoam cup with room temperature water. Record the amount of water.
Determine the initial temperature of the water using a candy
thermometer. Dissolve the salt in the water, mixing thoroughly.
Record the temperature of the solution and answer the following:
1) Was this reaction endothermic or exothermic?
2) Calculate the calories liberated or absorbed per gram of salt
using the total weight of the solution n determining the
number of calories. Assume the specific heat of the salt
solution to be the same as water.
Helpful conversion factors
See
1 gram is the approximate weight of one small paper clip.
C. Heat of Fusion of Ice
Heat 250 ml of water in a saucepan to about 60°C. Use a portion of this
water to warm a 2 cup Pyrex measuring glass. Pour 60ml (~1/4 cup) of
the heated water into the Pyrex glass and insert a candy thermometer.
Fill a Styrofoam cup with at least 50 g of chipped ice and pour off any
liquid present into the sink. Immediately read and record the volume
and temperature of liquid in the Pyrex glass and pour the entire quantity
of water over the ice. Stir until the water temperature reaches 2°C or less.
Record the final temperature and immediately pour all of the ice water
back into the Pyrex glass, draining the ice well.
Record the new volume of water in the Pyrex glass.
The increase in liquid volume came from the ice. The heat necessary to
melt the ice was provided by the warm water.
Answer the following questions:
1) How much ice melted?
2) How much heat was needed to melt this ice?
D. Heat Transfer in the Body
The following experiments will illustrate some heat transfer processes
which can occur in the body. For all experiments, calculate the amount
of heat given off or absorbed the body.
(1) Get a piece of ice about 1g in mass. Rub it on your arm until it melts.
Did you feel the heat leaving your body to melt the ice?
How much heat was needed to melt this 1g sample of ice to
warm water at normal body temperature?
(2) Spread about 1g (1ml) [1 teaspoon = 5ml] of tap water over your hands and arms and allow them to dry by evaporation.
Calculate the amount of heat supplied by your body to warm
the water from room temperature to body temperature and to
Evaporate it.
Assume the heat of vaporization of water is 520 calories/gram at body temperature)
(3) Rubbing alcohol (isopropyl alcohol) is sometimes applied to the skin
to help reduce a fever by removing heat by evaporation of the
alcohol. Repeat experiment (2) above using room temperature
rubbing alcohol in place of the water.
Assume the heat of vaporization of rubbing alcohol is 173 calories / gram )
Assume the specific heat of alcohol to be the same as water.
(4) You may have had a hot drink at breakfast this morning. Assume
you drank 250 ml of this hot water at 80°C and this amount was
cooled by your body to 37°C (98.6°F). How many calories were
supplied by your body?
EXPERIMENT II : Mechanical Digestion
The following experiment is designed to have you follow the events of mechanical digestion. You will need a paper and pen/pencil to record your observations, a half cup of water, two saltine crackers, a watch with a second hand, a stethoscope, mirror, rubbing alcohol (isopropyl alcohol), and two cotton balls.
Clean the earpieces of the stethoscope using the cotton balls dipped in the rubbing alcohol. While standing in front of a mirror, think about eating the crackers and drinking the water. Imagine how good they will taste as an appetizer to lunch or dinner. Place the earpieces of the stethoscope on your ears and gently tap the round bell diaphragm. You should be able to hear the taps. Place the bell diaphragm over your stomach between the medial margins of the rib cage. For the next minute, think about eating, smell the crackers, look at the water, and listen to your stomach. Record your observations.
Next, place the two saltine crackers in your mouth and begin chewing slowly for 30 seconds. Note the movement of your tongue and teeth during this time and observe the movements of your jaw and muscles.
Note any changes in flavor that you may detect while chewing the saltines.
When you are ready to swallow, place the bell diaphragm of the stethoscope to your throat and listen to the sounds and observe the movements of the laryngeal muscles in the mirror when you swallow.
Next place the bell diaphragm of the stethoscope over your abdominal wall approximately two finger widths (~1 inch) below the xyphoid process of the sternum. Note any more gastric sounds for the next minute as food begins to enter the stomach.
With the stethoscope still in place over the stomach, drink the water and listen for two sounds as the water travels down the esophagus. The first sound is when the water hits the gastroesophageal sphincter and the second sound is when the sphincter opens to allow water to enter. Record the time interval between these two sounds as it reflects the amount of time for a peristaltic muscle contraction in the esophagus to travel down to the stomach.
Answer the following questions:
1) What tissues/organs were used in the mouth to aid in mechanical digestion?
2) Why was there a change in the texture of the cracker?
3) Why was there a change in the flavor of the cracker?
4) What muscles are used in swallowing and name a cranial nerve that controls these muscles.
5) What was producing the gastric sounds?
6) What is the purpose of the gastroesophageal sphincter?
7) Define peristalsis and segmentation.
8) Where is the stomach and how much can volume can it hold?
9) What is the purpose of mechanical digestion?
10) What are the three gastric phases of secretion?
EXPERIMENT III: Macromolecules
A. Starch Identification
Recall that starches are part of the carbohydrate class of macromolecules
known as polysaccharides. This polymer is a series of glucose molecules
linked in long chains that occur in two forms: amylose and amylopectin.
To detect the presence of starches, iodine is used as it forms a complex that appears blue-black. If a starch is partially digested it will form dextrins and maltose and a starch will fully be digested to glucose molecules. None of these digested products reacts with iodine and a “clear” result will be seen.
You will need tincture of iodine (available at grocery/ drug store pharmacy), measuring spoons, measuring cup, distilled water, corn starch, one piece of white bread, laundry starch, white paper, canned corn in water, canned peas in water, canned string beans in water, slice of raw Idaho potato, saltine cracker, and clear plastic cups.
In a clear plastic cup add about ˝ cup water and mix with 3 tablespoons
of corn starch. Add several drops of iodine and record results.
On one piece of bread, drip several drops of iodine and record results.
In a clear plastic cup, spray laundry starch and coat sides and bottom.
Add water to suspend particles and several drops of iodine and
record the results.
On a piece of paper, drip several drops of iodine across the page and
record the results.
Get three clear plastic cups and label one corn, one pea, one string beans.
Pour off some liquid (1 tablespoon) from each of these cans into the appropriate cup. Add several drops of iodine and record the results.
On the slice of potato, drip several drops of iodine and record the results.
Using the saltine cracker, and place in your mouth. Chew bread for about
4- 5 minutes.
Spit out chewed portion into clear plastic cup and add water
to help liquefy if needed.
Add several drops of iodine and record the results.
Answer the following questions:
1) Which of the above products contained starch?
2) What chemical process is occurring in the mouth?
3) Name the glands and enzyme used to help digest carbohydrates.
4) Why did the saltine cracker taste sweet?
5) Potatoes contain amylose and amylopectin and both react with iodine.
Did you notice two different color changes? If so, why
B. Protein Experiments
Recall that proteins are chains of amino acids and form 3-D
structures that allow for chemical reactivity and function.
(1) Protein Denaturing
Obtain 3 eggs, egg white separator, glass bowl, whisk, fry pan,
laundry detergent and three ceramic bowls.
Separate egg whites from the egg yolks and place the
egg white from each egg into one of the ceramic bowls.
Egg whites are composed of albumin, a common protein
found in the human body. Pour one egg white into the glass
bowl and use the whisk to beat the egg white until fluffy.
Put bowl aside and let sit.
Next take another egg white and put into frying pan, set
To medium heat on the stove and cook for two minutes.
Turn off heat and remove pan from stove. Let sit.
In the last bowl containing the third egg white, add one
tablespoon of laundry detergent. Mix and let sit.
a) Define denature
b) Did the egg whites ever return to their “normal” form
after each experiment?
c) What did the whisk simulate?
d) How does temperature affect the peptide bonds?
e) How might pH affect the peptide bonds of proteins?
(2) Enzyme function
Rennin is an enzyme that acts on the soluble milk protein
caseinogen to coagulate milk and produce an insoluble form
called casein. The thickened consistency of the milk slows
its movement through the digestive tract.
For this experiment, obtain rennin tablets from the grocery or
Whole food stores. Dissolve two tablets in two tablespoons of
water. Divide this solution in half and put in small juice glasses.
Add milk to an equal volume. Place one juice glass with the
Rennin, water, and milk into a Styrofoam cup filled with ice.
Place the other glass with rennin, water, and milk in your hand.
What approximately three minutes. Observe the two glasses.
After the milk coagulates, the semi-solid component (curds)
can be separated from the liquid portion (whey). Whey is high
in lactose and the dairy industry dries the whey for use in processed foods. The curds are cultured and aged to make cheese.
Answer the following questions:
Protein experiment continued
a) Is this enzyme reaction temperature sensitive?
b) What household products contain whey?
c) Why would rennin be an important enzyme for
infants to produce?
C. Fat Experiment
Recall that triglycerides are the primary lipids for energy in the diet.
The enzymes necessary for fat digestion are water soluble, whereas the
fat is not water soluble and forms big droplets preventing adequate
digestion. Bile is needed to physically separate the fats into smaller
droplets called micelles. These smaller particles help increase the
surface available for enzymes to start the chemical digestive processes.
Obtain three small glass jars with lids (or use saran wrap as a lid and secure with rubber bands), vegetable oil, water, liquid dishwashing detergent, measuring cup, and green food coloring.
In two of the jars add ˝ cup vegetable oil and ˝ cup water.
Observe the interaction of the oil and water. Place lids on both jars
and shake vigorously. Observe interaction of the oil and water and let
sit for 5 minutes. In the third jar add 1 tablespoon of liquid dishwashing detergent and 1 teaspoon green food coloring. Mix well.
Take one of the original oil/water jars and add the green mixture.
Replace lid and shake well.
Observe interaction of oil and water and green detergent.
Answer the following questions:
(1) Define emulsification
(2) Define micelle
(3) Where is bile made and stored?
(4) What enzymes are used for chemical digestion of fats?
(5) What would happen if fats could not
be adequately digested?
EXPERIMENT IV: Label
Use products found in your kitchen or grocery store and categorize the ingredients in the following categories: carbohydrates, fats, proteins, minerals, vitamins, water, and food additives (anticaking agents, chemical preservatives, emulsifying agents, nutriceuticals, sequestrants, stabilizers, synthetic flavorings, and miscellaneous additives).
Make your list using at least five products and compare the nutritional value of each product selected.