Download Microbial Discovery Activity What Makes Flatulence

Microbial Discovery Activity
What Makes Flatulence
Authors
Andrew Gilbert, PhD
Assistant Professor, Science Education
Kent State University
E-mail address: [email protected]
Tracy Meilander, PhD
Cleveland Clinic Foundation
Cleveland, OH
Shannon Helfinstine, PhD
Scientist
Oringen, LLC
Talmadge, OH
Christopher J. Woolverton, PhD
Professor, Biological Sciences
Kent State University
Intended Audience
K-4
5-8
9-12
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Activity Characteristics
Classroom setting
Uses hands-on manipulatives
Requires group work
Requires more than one class period
American Society for Microbiology
Education Department
1752 N Street, NW
Washington, DC 20036
[email protected]
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Introduction
Description
Using guided inquiry, students discover the role of bacteria in the large intestine and their ability to
produce gas during the digestive process.
Abstract
In this exercise, students use a controlled environment to demonstrate the build up of gases in the
large intestine. Through their observations, they will better understand the mechanisms that create
flatulence (passing gas) and how microorganisms can be beneficial to overall health.
Core Themes Addressed
General Microscopy Concepts
Microbial Cell Biology
Microbial Genetics
Microorganisms and Humans
Microorganisms and the Environment
Microbial Evolution and Diversity
Other -Common properties of life;
Cellular components
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Keywords
Digestion, intestines, bacteria, chyme, flatulence, carbohydrates
Learning Objectives
By completing this activity, the student will be able to:
1) Investigate the factors that lead to the release of gas from our large intestines.
2) Recreate these factors within a scientific setting.
3) Hypothesize how gas is made in the large intestine based on observations of their
experiments.
4) Articulate why this process is important for digestion and overall health.
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National Science Education Standards Addressed
Content Standards 5-8:
Science as Inquiry:
Students will perform guided inquiry concerning the role of bacteria within the digestive process. This
will include observation and hypothesis building based on empirical evidence.
Life Science:
Students will understand how microorganisms (bacteria) can create a volume of gas from the break
down of carbohydrates that go undigested by the stomach and small intestine.
Science in Personal and Social Perspectives:
This investigation will facilitate student understanding for the important role that microorganisms
play in the bodily functions of the human body.
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Teacher Handout
One of These Things is Not Like the Other
Student Prior Knowledge
Students may not have heard of the word “flatulence” before, but they most likely have had some
experience with it. Flatulence is the word scientists use to refer to the gas that builds up in your
lower intestines and is expelled through the anus. You may want to give students a chance to be silly
to get over their initial embarrassment about the content. It may even help to have them share the
words they use at home for “passing gas” and remind them that for the remainder of the class
everyone will be expected to utilize the words that scientists use. The build up of gas comes from two
main sources 1) air swallowed while eating and/or drinking and 2) by the breakdown of
carbohydrates in the intestines. This lesson will deal with the second source of gas that leads to
flatulence.
Teacher Background Information
Often Middle School students are extraordinarily interested in how their bodies work and often are
even more intrigued by the gross things their bodies do. Often these notions of stinky breath or
intestinal gas are often off limits to talk about because they are seen as distasteful and often give
students notions that these things, which happen to everybody, are bad things. Obviously, we do not
want to encourage students to pass gas proudly as part of an experiment, but it is important that
students be given the chance to better understand the phenomena that they experience in their
everyday lives. If you are nervous about discussing these ideas with children realize that we are
sticking to the science behind how and why these things happen. It is essential to stress that
students need to be mature while discussing these ideas as scientists, but certainly expect some level
of giggling as they get used to talking about these ideas.
Necessary Content Background
This activity is meant to facilitate student visualization for the mechanisms that create the build up
gases in the large intestine. Everybody has them. Many deny it, but everybody does it. Flatulence
is simply an extension of the digestive process taking place within our bodies. In general, flatulence
occurs after food has been chewed, sent to the stomach, and the resulting mineral/vitamin rich goo
(Chyme) is transported to the small intestine. Here the minerals/vitamins, etc. are absorbed into the
blood stream and made available to the body for energy. However, there are some parts of the food
that cannot be broken down through this process (generally insoluble and soluble fibers and some
sugars). These bits of fiber and sugar are mixed in with the rest of the partially digested, semi-liquid
mass that scientists refer to as chyme. These are undigested in the small intestine and are pushed
into the large intestine by the process known as peristalysis.
Foods that are high in carbohydrates will create more flatulence than foods, which are high in fat
and proteins. The large intestine is home to millions of bacteria that consume and further digest
much of the remaining carbohydrates. These carbohydrates include both sugars and fiber. There are
two types of fiber: soluble and insoluble. Insoluble fiber passes through the colon relatively
unchanged by the digestive process. Conversely, soluble fiber is broken down by dissolving in water
to form a gel, which is fermented by the bacteria in the colon. During the fermentation process, the
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bacteria release small amounts of gas that build up inside your large intestine until it is released
through the rectum as flatulence.
Humans develop a lifelong symbiotic relationship with microbes soon after birth. As an infant
acquires these microbes (often referred to as the normal microbial flora), they colonize the newborn,
with internal flora being acquired through its diet. More than 90% of the intestinal flora of breastfed infants belong to the Bifidobacteria, with Enterobacteriaceae and enterococci represented in
smaller numbers. Bottle-fed infants have a much smaller number of intestinal bifidobacteria. The
predominance of bifidobacteria is lost when the infants take solid food and cow’s milk. Furthermore,
other bacteria increase to outnumber bifidobacteria.
The first part of the small intestine (duodenum) contains gram-positive cocci and rods. Enterococcus
faecalis, lactobacilli, diphtheroids, and the yeast Candida albicans are typically found in the next
section of the small intestine (jejunum). It is in the last section of the small intestine (ileum) that
the flora are more like those in the large intestine (colon). The colon supports the largest community
of microbes in the body, often around 1012 organisms per gram of wet feces. The colonic bacterial
population usually doubles once or twice a day. Over 400 different species have been found and
consist primarily of anaerobic, gram-negative and gram-positive bacteria.
Of note, the colonic bacterium Bacteroides thetaiontaomicron is able to degrade complex dietary
polysaccharides. Methanogenic bacteria also degrade dietary components, converting hydrogen and
carbon dioxide products of fermentation to methane. It should be emphasized that the actual
proportions of individual colonic bacteria, and thus fermentation byproducts, depend largely on a
person’s diet.
Class Time
60 minutes or one class period plus an extended observation schedule (4 days).
Teacher Preparation Time
The preparation time for the activity will vary depending on access to a blender or food processor.
This should only take a few minutes to peel and blend. It is best to do this right before it is to be
distributed to student groups. If unavailable then students will need to mash the banana in their
groups. Beyond mashing the bananas the prep time is relatively small. You will need to collect the
materials and make copies of the student handouts, which could be done in less than 30 minutes.
Overview
This demonstration will work to recreate the digestive processes that are taking place within our
large intestine. The first stage will be to mash or use a blender/food processor to turn bananas into
mush. Use one banana for each group of students (Try to limit groups to four or fewer students)
than divide banana goo evenly among groups. Have students place banana mush into their
Erlenmeyer flasks and provide them with the observation page. Observe the banana for three to five
days. It will also help if the banana jars are kept in warm environment.
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Materials and Equipment
Erlenmeyer Flask (one for each group)
One medium size balloon (one for each group)
One banana (per group)
Student activity page
Plastic cups (for banana goo)
Plastic spoons (for putting banana goo into flask)
Piece of string (for each group)
Ruler (for each group)
Methods
1) Blend bananas until mixture reaches a smooth and creamy texture.
2) Divide banana mixture equally among the groups. If you have six groups, use six bananas
and try to separate them equally into the plastic cups and provide them to the students. If no
blender or food processor is available have students mash banana with a fork in the plastic
cups.
3) Have students put banana mixture into flask and affix balloon onto top of flask
4) Then (using student activity page) have students decide on a place to put the balloon
mixture. It will help if the mixture is placed in a warm place, which will help to increase the
bacterial activity. It is okay if some students choose to put their mixture in a place that may
not yield great results as long as there is another group to compare the results with.
5) After students set-up their flask/balloon ask them to decide as a group, the location in the
classroom.
6) Ask the students to record on their activity page why they chose the particular location in
the classroom, and to answer three initial questions to get them thinking about the
experiment:
a. What is their prediction for what will happen to the goo in the flask?
b. What will happen to the balloon?
c. Why do they think these things will happen?
7) Design an observation schedule over a five day period – it may be best to start the lab on a
Monday so that you could observe everyday through Friday.
8) After day one set aside ten minutes each day to observe the mush – have students use their
observation sheet. Have students devise a way to use the string to measure the
circumference of the balloon.
9) On the last day of observations have students answer the questions under number four on
the student activity page
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Suggestions for Assessment
After all observations have been completed, ask the students to answer the following conclusion
questions in their worksheet. They can also present their findings orally in the front of the
classroom.
a. What happened to the banana goo?
b. What happened to the balloon during the five days? How did the circumference of the balloon
change over this time?
c. What is your hypothesis for why this occurred?
d. What is causing the changes?
e. Imagine the flask represents your large intestine, what would be inside the balloon?
f. What are your thoughts for how this process helps our body function?
Possible Answers
1. Prediction Questions
These questions are designed to enhance and develop student critical thinking and will not
necessarily have one correct answer for each assessment point. Often, students will be describing
their observations and what may be happening in the goo to create those conditions. The following
section is offered as a guide for what teachers could expect from students during this lesson.
a – The student prediction will exhibit a high degree of variation. Try to push students beyond
simplistic answers i.e. “banana will go bad” or “smell stinky.” Make sure they articulate ideas
with as much detail as possible, including the time it will take for their changes to occur.
b – Again have students be as detailed as possible here. Their answers may vary from “nothing”
to the balloon being “blown up,” have them articulate the degree to which these things will
happen as well as the time it will take for these changes to occur. They should also be able to use
pieces of string to keep track of the changes in the balloon circumference and relate this the
overall volume of gas.
c – This section will help identify student prior knowledge particularly if they make any
connection to the breakdown of the banana goo as being related to the presence of bacteria.
2. Location of the Flask
Students may have some ideas concerning environmental factors can influence the breakdown of
organic materials. It will help speed up the breakdown process to put the flasks in a warm area of
the classroom that will enhance the growth of bacteria and the subsequent breakdown of the banana
goo.
3. Observations
The observation chart can be altered to your teaching preference, however in its current form it
focuses on describing the changes of the banana. The goal of the lesson is to facilitate students in
associating the breakdown of the banana goo (sugars in particular) can result in the build up of
gases. This mimics the creation of farts within our bodies.
4. Conclusion Questions
At the conclusion of the observation schedule, the following questions will help students focus on
the changes that have taken place.
a – Banana goo will turn colors from creamy light yellow to blackish brown. It may also build up
water vapor/water along the sides of the flask.
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b – The students should observe the balloon filling slowly with gas over the course of the week.
The rate will depend on amount of goo, size of balloon and flask, and the environmental
conditions in which the flask has been placed.
c – Students may say the banana is “breaking down” or “rotting” try to have students articulate
what is making the goo breakdown. This is where you will want to introduce the role of bacteria.
As the bacteria breakdown (ferment) the sugars, each bacterium give off a tiny amount of gas.
However, because of the large number of bacteria the tiny amounts of gas build to create a large
enough volume of gas to expand the balloon.
d – The large intestine is home to millions of bacteria that consume and further ferment the
unused sugars and soluble fiber. During this process, the bacteria release small amounts of gas
that build up inside your large intestine until it is released trough the rectum. Students may say
that as food moves through the intestine and continues to break down that it will give off gas
that builds up. This may be an area that you can address after the lesson or during the
discussion of the questions and relate to students the role of bacteria in creating the gas.
e – Student answers may vary greatly on this question. Hopefully, students can connect bacteria
in the intestine to a digestive process occurring within the body.
Additional Resources
Branzei, S. (2002). Grossology: The science of really gross things. Price Stern Sloan.
Insel, P., Turner, R. & Ross, D. (2006). Discovering Nutrition. Boston, MA: Jones and Bartlett.
Whitney, E., Rolfes, S. (2008). Understanding Nutrition. New York: NY: Thomson Wadsworth.
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Student Handout
One of These Things is Not Like the Other
Introduction
The large intestine is home to millions of bacteria that consume and further breakdown the unused
sugars and some types of fiber. During this process, the bacteria release small amounts of gas that
build up inside your large intestine until it is released trough the rectum. In this exercise, you will
use a controlled environment to demonstrate the build up of gases in the large intestine. Through
your observations, you will gain a better understanding about the mechanisms that create flatulence
(passing gas) and how microorganisms can be beneficial to our overall health.
Student Background Knowledge
This activity is meant to demonstrate for the build up gases in the large intestine. Everybody has
had intestinal gas at some point. Many deny it, but everybody does it. Flatulence is simply an
extension of the digestive process taking place within our bodies. In general, flatulence occurs after
food has been chewed, sent to the stomach, and the semi-digested goo (Chyme) is transported to the
small intestine. Here the minerals/vitamins, etc. are absorbed into the blood stream and made
available to the body for energy. However, there are some parts of the food that cannot be broken
down through this process. These bits of leftover food particles are made up of a nutrient called
carbohydrates. Typically, foods high in carbohydrates include: beans, sugars found in soft drinks,
fruit, potatoes, corn and wheat.
Foods that are high in carbohydrates will create more flatulence than foods, which are high in fat
and proteins. The large intestine is home to millions of bacteria that consume and further
breakdown much of the remaining carbohydrates. The bacteria release small amounts of gas that
build up inside your large intestine until it is released through the rectum as flatulence. The
following experiment will help to make better sense of this process and help you visualize what can
happen inside the colon when intestinal gas builds up.
Vocabulary
Bacteria – single-celled microorganisms that do not have a membrane-enclosed nucleus or organelles
such as mitochondria
Carbohydrates – compounds including sugars, starches and fibers that provide energy to the body
Chyme – a partly digested, semi-liquid mass of food that moves from the stomach to the small
intestines
Digestion – the process by which food is broken down and absorbed into the body
Flatulence – the release of gas from the intestines
Large intestine – the tube extending from the small intestine to the anus
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Materials check list (Per group)
Erlenmeyer Flask
One medium size balloon
One banana
One plastic cup
One fork and spoon
One String
Worksheet
Observation chart
Procedure for Participants
1. For this exercise you will work in groups as assigned by your teacher.
2. Decide who in the group will be responsible for record-keeping (the scribe), and who will
provide the oral report at the end of the week.
3. Gather all your materials.
4. Place banana goo into your flask and fit balloon over top of the flask.
5. Dispose of all the extra materials as instructed by your teacher.
6. Work as a group to answer the 3 prediction questions found in your worksheet.
7. As a group, decide where in the classroom you will set-up your flask. Why did you
this location? Use your worksheet to answer this question.
choose
8. For the next five days you will observe your flask. Record your observations in
"observations chart."
the
9. On day 5, after all observations have been completed answer the conclusion
your worksheet.
10. Each group will present an oral report of their findings.
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questions in
Student Observation Chart
Day
One
Sketch
Group # ____________________
Description of Banana Mush
Date __________________
What changes are taking place?
Circumference:
Two
Circumference:
Three
Circumference:
Four
Circumference:
Five
Circumference:
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What Makes Flatulence Exercise
Worksheet
Group #_____________
Date__________________
Predictive Questions
1.
What is your prediction for what will happen to the goo in the flask?
2.
What will happen to the balloon?
3.
Why do you think these things will happen?
Location of the Flask.
1.
Why did you choose this location?
Conclusion Questions
1.
What happened to the banana goo?
2.
What happened to the balloon during the five days? How did the circumference change
over time? How does that relate to the volume gas created in the balloon?
3.
What is your hypothesis for why this occurred? What is causing the changes?
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4.
Imagine the flask represents your large intestine, what would be inside the balloon?
5.
What are your thoughts for how this process helps our body function?
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