I. Food is Fuel! Transfer of energy in the context of exercise
metabolism
II. Developers: Katie Mouzakis1 and Dr. Gary Diffee2
1
Department of Biochemistry, UW-Madison
2
Department of Kinesiology, UW-Madison
III. Description and Justification:
The students enrolled in Biology375: Exploring Biology are first-year, first generation college
and minority students with an interest in learning more about the biological sciences. The
seminar-style course provides an introduction to the five major biological concepts, referred to as
the “Five Big Ideas in Biology”, including: evolution; pathways and transformations of energy
and matter (transfer of energy); information flow, exchange and storage (transfer of
information); structure and function; and systems. Additionally, students will consider what it is
that biologists actually do and study. Personal experience and past teaching experience indicate
that students struggle with 1) understanding the relationships between the big ideas in biology, 2)
understanding how the food one consumes is converted into energy, and 3) how different sources
of energy are used in different situations. This teachable unit attempts to convey the relationship
between metabolism and energy transfer at both the macroscopic and microscopic levels. The
concept is presented in the context of exercise metabolism and hitting “the wall” in a marathon.
The learning goals for the course include: 1) students will understand the interrelatedness of the
“Five Big Ideas in Biology;” 2) students will understand what a biologist does, the types of
questions biologists study, and possible careers in the biological sciences; and 3) students will
learn how to pursue an interest in biology inside and outside the classroom. The learning goals
were developed based on the following: 1) unit design focusing on achievement of course
learning goals; 2) maintaining and communicating high expectations for students higher order
cognitive skills; 3) keep the material relatable and relevant, 4) frequent assessment and timely
feedback, and 5) ignite and nurture student passion. This unit will directly help them understand
metabolism as an example of energy transfer at the macroscopic and microscopic levels. These
teachable unit materials are designed for early college students with varied backgrounds in
biology. For more advanced students, more in depth exploration of the metabolic pathways
could be warranted. Additionally, amino acid metabolism could be included.
Learning Goals & Outcomes
Primary learning goals and outcomes (course goals)
1
2
Learning Goals
Students will understand that cells require
energy to carry out normal functions. That
energy is extracted from compounds we
consume and is converted into ATP.
Students will understand how the energy is
stored (glycogen, fats).
Page 1
Learning Outcomes
Students will be able to explain why a
cell would need ATP. (Blooms level 2)
Students will be able to explain how
energy is stored for future use (short
3
Students will understand that glycogen and fats
are used to make ATP.
4
Students will understand which stores of
energy are used at different times when
exercising (glycogen, then fats).
5
Students will understand what determines
if something gives us energy, specifically
how food can be considered fuel.
term and long term situations). (Blooms
level 2)
Students will be able to list the three
different types of molecules used to
make ATP. (Blooms level 1)
Students will be able to put the different
steps of metabolism into chronological
order. (Blooms level 3)
Students will be able to evaluate energy
drinks, bars, and gels as potential energy
sources. Students will determine
whether or not they are based on the
product ingredients. (Blooms level 6)
Secondary learning goals and outcomes (unit goals)
6
7
Learning Goals
Students will understand what types
of fuel are used during exercise and
why glycogen would be
preferentially used instead of fats.
Students will understand how
energy is used during exercise.
Learning Outcomes
Students will be able to differentiate between a
fatty acid and glucose monomer- indicating which
yields more ATP and which always requires
oxygen for its metabolism. (Blooms level 4)
Students will predict how different energy
supplements would affect a marathon runner if
consumed during the race. They will create a
written suggestion explaining whether or not the
current race plan is likely to help the runner avoid
hitting “the wall”. They will explain why this in
the case. (Blooms level 4, 5)
Scientific Teaching:
Diversity- A variety of activities will target students many learning styles, including
visual, auditory, and reading/writing. Students who prefer dynamic learning (strip sequence &
case study) and quiet learning (mini-lecture and guest speaker) will both be involved at various
points during the lesson. All students will be included during the strip sequence because they
will have to work with a partner. Student interested in nutrition and exercise will be included in
this teachable unit because they are critical components of lecture and discussion. Students with
auditory deficiencies might not be included during lecture if they cannot hear the speakers. For
those reasons, the presentation slides will be made available online for students to access before
class.
Active Learning- Mini-lectures and the individually completed strip sequence will be
completed during lecture. In discussion, students will apply what they have learned in a lecture
to a case study. They will work in groups to complete the majority of the case study. This will
require them to actively ask questions as well as teach other students material they may have
missed. For homework, students will each need to write an article responding to the case,
requiring them to evaluate and synthesize information.
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Assessment- A pretest will measure the students’ prior knowledge of energy transfer and
metabolism. In-class activities will assess students’ comprehension (strip-sequence). The case
study will measure student’s ability to apply, analyze, synthesize and evaluate the use of energy
supplements during exercise.
Assessment Activities:
Before class- 1) Students will complete an online quiz assessing their familiarity with
metabolism (this will be part of the precourse survey), 2) Students will watch 4 videos
teaching them how muscles function. They will use what they learn to answer key
questions about muscles and ATP usage.
Lecture: Students will complete a strip sequence that orders the different steps in
metabolism. Students will predict and explain what changes in fuel metabolism would
occur for a runner who has undergone increased training
Discussion: Students will complete a case study requiring them to apply what they
learned during lecture to analyze and evaluate different runners marathon nutrition plans
to avoid hitting “the wall”. Students will need to answer a list of short answer questions
and fill out the table with the supplement ingredients. They will use the answers to these
questions to help them write up their homework.
Post class- students will complete the case study and turn it in their written responses
electronically. Students will need to demonstrate evidence of learning in order to get the
full 10 pts. Students who write a response that does not highlight any of the material
learned in the case study or in lecture, but is still relevant to the case, will only receive 7
pts.
Classroom Activities:
Lecture:
1) Engage and Elicit
 A mini-lecture will be given on all of the big ideas surrounding metabolism.
2) Explore & Evaluate
 Students will need to put all of the metabolic steps covered in order of occurrence
using a strip sequence.
3) Engage and Elicit
 A mini-lecture will be given on metabolism in the context of exercise. Students
were asked to apply what they are learning to a multiple choice question on the
changes in carbohydrate and fat utilization during a marathon occurring with
increased training.
Discussion Section:
1) Extend
 Students will complete a case study evaluating the marathon race strategies of a
marathon runner in the context of metabolism.
2) Evaluate
Page 3

Students will evaluate the ingredients in the marathon runner’s supplements of
choice for carbohydrate and fat content. They will use what they know about fuel
usage during endurance exercise to evaluate the usefulness of these supplements.
3) Extend
 Students will create written articles addressing the merits (in terms of energy
availability and exercise metabolism) of the planned race strategy. They will
explain how the strategy could affect their chances at hitting “the wall”.
Overall Plan (Class on 4/17/2012)
Before class:
Transfer of Energy –Pre-class HW due on 4pm on 4/17/12
Reading Assessment- turn into dropbox “HW wk 13 reading assessment” (10 pts total/
2pts/question):
1) How do muscles function?
2) How does their structure affect their function?
3) How is ATP used for their function?
4) What would happen to muscle function if the cell ran out of ATP? Why?
5) What is one thing you learned from “Hitting the Wall” by Sara Latta?
To complete 1-4, you will need to watch 4 videos. To complete question 5, you will need to
read the article.
Links: Videos and transcripts are available with this unit. Videos can be downloaded from the
original website. The transcripts are also available there, but have been copied here for
completeness (pg 26-32)
Video 1- http://www.interactive-biology.com/2012/an-introduction-to-skeletal-musclecontraction/
Reference: Samuel, Leslie. “041 An introduction to Skeletal Muscle Contraction”, March 8,
2011. http://www.interactive-biology.com/2012/an-introduction-to-skeletal-muscle-contraction/
Video 2- http://www.interactive-biology.com/2032/how-the-release-of-calcium-ions-results-inmuscle-contraction-episode-42/
Reference: Samuel, Leslie. “042 How the Release of Calcium Ions Results in Muscle
Contraction”, March 9, 2011. http://www.interactive-biology.com/2032/how-the-release-ofcalcium-ions-results-in-muscle-contraction-episode-42/
Video 3- http://www.interactive-biology.com/2133/043-the-details-of-muscle-contraction/
Reference: Samuel, Leslie. “043 The Details of Muscle Contraction”, March 23, 2011.
http://www.interactive-biology.com/2133/043-the-details-of-muscle-contraction/
Video 4- http://www.blackwellpublishing.com/matthews/myosin.html
Reference: Matthews, Gary. Neurobiology Molecules, Cells, and Systems, 2nd edition,
“The mechanism of filament sliding during contraction of a myofibril”. Blackwell
Publishing, http://www.blackwellpublishing.com/matthews/default.html
Page 4
Reading “Hitting the Wall” by Sara Latta, Marathon and Beyond, September/October 2003
issue, http://www.marathonandbeyond.com/choices/latta.htm
Page 5
Lecture:
Time
Activity
-5 min Rocky soundtrack songs are
playing in the background
and students get seated
1 min Introduction to learning
outcomes
10
min
Mini-lecture - introduction
to metabolism
1) What is energy?
2) Why do we need energy?
3) How do we get energy?
4) Energy currency (ATP)
and storage (glycogen and
fats)
5) How do we use ATP?
6) How do we make energy?
Glycogen and fats
7) How do we store energy?
Glycogen and fats
Students complete the stripsequence on the events in
metabolism. They do this as
a think-pair-share
Purpose
To get students in the right mindset to
talk about intense endurance exercise
If students know the intended
outcomes of the lecture, they will
understand why it is important when
we go over the material needed for
them to be able to accomplish these
tasks
To introduce the students to the big
ideas related to energy transfer and
metabolism.
Students volunteer answers to #2 (but
only briefly)
An economic analogy is used to allow
students to connect their prior
knowledge to what they are learning
about energy in the cell
For students the students to take what
they have learned, connect it to prior
knowledge, and learn how to place the
metabolic steps in order. This gives
them an opportunity to assess their
understanding of the material and the
instructor a chance to see where they
are at before moving on
30min Guest lecture on exercise physiology & metabolism by Dr. Gary Diffee
Quick reminder of what we just
1 min Introduction to exercise
metabolism- where do we get talked about and of what muscles
ATP?
look like, which students were
introduced to in their pre class HW
To show the difference in energy
5 min Talk about the role of
mitochondria and oxygen in
production for fats and glucose. To
ATP synthesis
reinforce the role of oxygen and
mitochondria in metabolism
To demonstrate how different types
5 min What types of fuel do your
muscles use during low,
of fuel are preferentially used during
moderate, and high intensity different activities- high intensity =
activities?
marathon running
10
min
Page 6
Goal
1,2,3
4
5, 6, 7
3
6
6, 7
5 min
10
min
What happens when you run
out of your limited muscle
glycogen stores?
What are the effects of
training on the way your
body uses fuel?
If extra time is available
Gary will talk about his
research on exercise
metabolism
To show students what your body
does for fuel when glycogen stores
run out
Students do a think pair share activity
to predict how fuel utilization
changes with training. This primes
them to receive that information.
To introduce students to a type of
research that is conducted on campus
and is related to the current material
7
7
Discussion: Note: the classroom should be divided into groups and groups will work together to
complete the case study. They will need to finish it as HW individually.
time
5 min
37 min
5 min
3 min
activity
Introduction to the case study In discussion today students will
use what they have learned about
exercise metabolism to complete a
case study.
 What you do not finish is class
will need to be completed as HW
 Students can work in groups, but
must write their own answers to
the questions.
 There are three different runner
race fueling strategies that can be
divided amongst the groups.
Students will work in groups to complete
the ingredients/research table and answer
all of the short answer questions. Many
of the short answer questions they should
be able to answer based on what they
learned during lecture.
As a group have students volunteer the
answers to all of the short answer
questions. You can use these questions
on the exam so it is important that
students know the answers
purpose
To explain what students
will be doing in class
goal
For students to spend time
analyzing the ingredients
in the energy products to
determine if they actually
are good sources of energy
for a marathon runner
This gives students an
opportunity to assess their
understanding of the
material as a group and
correct any misconceptions
5, 6,
7
Check that each student has completed
the table and case study- give them 5
participation points for this. Reiterate
that they have a HW assignment
The 5pts are incentive for
students to answer the
question and complete the
table. This is necessary for
Page 7
5, 6,
7
them to complete their HW
successfully.
In class handout:
What happened to your breakfast?
In the morning you wake up hungry. While you were sleeping (fasting), your brain continued to
use glucose for energy. As a result, your blood glucose levels drop steadily. When they reach a
specific threshold, your brain releases a hormone signaling for the synthesis of glucose. What
happens next?
Glucose monomers are released into the blood from the digestive system,
increasing the blood glucose level
Excess glucose in the blood is absorbed by the liver and muscles
Glucose is absorbed by the brain
You consume a gigantic bowl of oatmeal (rich in carbs), which is digested and
converted into glucose monomers
The brain uses glucose for the synthesis of ATP
Glucose is used for fatty acid synthesis
Glucose is converted to glycogen for immediate storage
Fat
100% -
Effects of Training
Carbohydrate
Percent
Fuel
Utilization
Rest
Exercise Intensity
Page 8
Maximal
Exercise
Discussion:
Students’ will complete a case study regarding the race nutrition race strategy of three different
marathon runners. As the writers of the Marathon Master column in Runners’ world, students
will have to write a response to a marathon runner seeking advice on their marathon plan from a
metabolic perspective. Runners will be writing in response to the Marathon Master’s initial
article on hitting “the wall” and asking runners if they would like advice on their race strategy.
The students’ task is going to be to evaluate the runners plan in terms of what they know about
energy. They will do research on the ingredients in each of the supplements the runner is going
to take in the race determine how the different ingredients provide energy. They are also going
to have to predict how the chosen supplement plan may help or hurt the runner, and explain why
in the context of metabolism. Students’ will write up their answers in the form of an article for
the Marathon Master column in Runners’ World. In addition to their column response, they will
have to fill out case study questions along the way.
Case study: the purpose of completing the case study is for
students to be able to accomplish these goals:
Stated learning goals and outcomes:
#
Learning Goals
Learning Outcomes
5
Students will
Students will be able to evaluate energy drinks, bars, and gels
understand what
as potential energy sources. Students will determine whether
determines if
or not they are useful to someone running a marathon based
something gives
on the product ingredients. (Blooms level 6)
us energy
7
Students will
Students will predict how different energy supplements would
understand how
affect a marathon runner if consumed during the race. They
energy is used
will create a written suggestion explaining whether or not the
during exercise
current race plan is likely to help the runner avoid hitting “the
wall”. They will explain why this in the case. (Blooms level
4, 5)
Grading rubric for the 10 pt. written runner response:
10 pts - the student demonstrates evidence of learning- does their response include information
they would not have known before this unit. They should specifically describe the role of the
ingredients in energy production.
7 pts – the student writes an appropriate response, but leaves out details demonstrating their
understanding of the material. ATP isn’t mentioned at all, the role of fat and carbohydrates are
not differentiated, the effects of training aren’t discussed, etc.
Page 9
Handout for instructors
Lecture 4/17/12
0-12 min
Katie gives mini-lecture
12-17 min
Student complete and discuss the strip sequence
20 – 50 min
Gary gives his lecture
Discussion 4/17/12
0-5 min
CPP presentation
5-10 min
Explain the case study and get students started
10-40 min
Students work in groups on their case study, they complete it for HW
40-50 min
As a class go over the answers to the short answer questions. Each case study has the
same questions here. Student’s will get points for completing these, but won’t be getting
feedback on them as they will keep them to do their HW. [Note- students will likely see
very similar questions on the exam so it is important that you get through this part]
Note- please read the Case study in advance so you know what questions they will be
answering.
Students will get 5 points for filling out the table and answering the short answer
questions, but they will keep these when they leave class to assist them on their HW.
If they don’t make it through all of it that is ok, but make sure you go over the
answers to the short answer questions with the students.
Page 10
Pre-reading
Reprinted, with permission, from Marathon & Beyond (www.marathonandbeyond.com)
Hitting "The Wall"
by Sara Latta
If You Understand the Scientific Reasons Behind “The Wall,” You Should Be Able to Avoid It.
© 2003 42K(+) Press, Inc.
"It felt like an elephant had jumped out of a tree onto my shoulders and was making me carry it
the rest of the way in.”—Dick Beardsley, speaking of hitting "The Wall" at the second marathon
of his career, the 1977 City of Lakes Marathon.
“I wasn’t wanting to talk much. And when I’m not talking, you know I’m hurting.”—Don
Frichtl, a runner who encountered "The Wall" somewhere after mile 21 of the 2002 Chicago
Marathon.
“At around mile 23, I was beginning to feel like the anchor was out.”—George Ringler, speaking
of his 1991 Lake County Marathon.
“The Wall.” It evades easy definition, but to borrow from Supreme Court Justice Potter Stewart’s
famous definition of obscenity, you know it when you see it—or rather, hit it. It usually happens
around mile 20, give or take a couple of miles. Your pace slows, sometimes considerably. Some
runners say that it feels as though their legs had been filled with lead quail shot, like the stomach
of Mark Twain’s unfortunate jumping frog of Calaveras County. Others can’t feel their feet at
all. Thought processes become a little fuzzy. (“Mile 22, again? I thought I just passed mile 22!”)
Muscle coordination goes out the window, and self-doubt casts a deep shadow over the soul.
The bad news is that more than half of all nonelite marathon runners report having hit The Wall
at least once. The good news is that more than 40 percent of all nonelite marathon runners have
never hit The Wall. In other words, while it certainly doesn’t hurt to be prepared for the
possibility of hitting The Wall, doing so is far from inevitable.
Energy Dynamics 101
“Hitting The Wall is basically about running out of energy,” says Dave Martin, Ph.D., Emeritus
Regent’s Professor of Health Sciences at Georgia State University in Atlanta—chemical energy,
that is, stored in the form of adenosine triphosphate (ATP) and obtained from the breakdown, or
metabolism, of energy-containing fuel. The runner’s primary fuel sources are carbohydrates (in
the form of blood glucose and glycogen, a polymer of glucose stored in the muscles and liver)
and fats (free fatty acids in the bloodstream and muscle triglycerides, molecules containing three
fatty acids).
Fats might seem to be the logical first choice of fuel for endurance events; not only are they the
most concentrated form of food energy, but even the thinnest runners have enough body fat to
get them through 600 miles. Alas, it’s not quite that simple. Fatty acid metabolism requires
Page 11
plentiful circulating oxygen, a precious commodity when you’re running at marathon race pace.
Carbohydrate metabolism, on the other hand, requires less oxygen. In fact, cells can derive
energy from carbohydrates either aerobically (in the presence of oxygen) or anaerobically (in the
absence of oxygen).
If you start your marathon at a reasonable pace for you, your fuel consumption ratio will be
about 75 percent carbohydrates to 25 percent fatty acids, according to Martin. During the race, as
carbohydrate supplies begin to dwindle, that ratio changes as your body begins to rely more
heavily on fatty acids.
What does all of this have to do with hitting The Wall? Let’s start with the pace. It’s common, in
the excitement of the moment, to start out at a pace that’s too fast for you. Big mistake. Your
heart cannot pump enough blood to ensure a steady supply of oxygen to the muscles. At this
point, your muscles have no choice but to burn glucose in the absence of oxygen. The anaerobic
metabolism of glucose, as it’s called, is inefficient, yielding only about 1/18 as much energy (in
the form of ATP) as aerobic metabolism. To make matters worse, among the by-products of the
anaerobic metabolism of glucose are lactic acid and hydrogen ions. As these waste products
continue to accumulate in the blood and tissue, they will not only make your muscles feel as
though they are on fire, but they can also inactivate the enzymes that govern glucose metabolism.
You’re toast.
Even if you’re racing at a reasonable pace and you’ve done a good job of carboloading in the
days before the marathon, you still have only about 2,000 calories worth of glycogen stored in
the muscles and liver; that’s about enough to get you to—surprise!—mile 20. If you manage to
deplete your glycogen reserves, say hello to The Wall. As mentioned before, burning fatty acids
requires plentiful oxygen, so as fatty acid metabolism increases, your heart must work harder to
pump more oxygen-carrying blood to the muscles. It may be difficult or impossible to maintain
your pace, especially if you’ve lost enough water through sweat to become even slightly
dehydrated (this causes your blood to become thicker and therefore harder to pump). In addition,
fatty acid metabolism itself requires glucose; as someone once said, “Fat is burned in a
carbohydrate oven.”
Of course, you can do things to make sure you stay well hydrated and maintain an adequate
supply of glucose during the marathon, and you’re probably aware of most of them. Begin to
carboload a few days before the race to make sure that your muscles store as much glycogen as
possible. Fortunately, the old, frequently stressful and unpleasant depletion/loading program has
fallen out of favor with most runners. Martin recommends eating a balanced diet with a higherthan-usual percentage of carbohydrates as you’re tapering before the race. As the body increases
its glycogen stores, it also increases the amount of stored water, leading to slight weight gain but
also making more water available for sweat during the race.
Make sure that you are well hydrated before the race, and eat a light, carbohydrate-rich meal no
later than two hours before the race. And by all means take advantage of the water, sports drinks,
and other glucose-containing foods offered at the aid stations!
Page 12
Many people also find that sports gels provide quick boosts of energy, although Martin admits
that he is not a big fan of them. “Picture this poor soul who takes a blob of GU but doesn’t quite
manage to get a cup of water. Now he’s got this thick 100 percent solution of stuff in his stomach
that he can’t absorb. I’m a firm believer in energy drinks rather than just water.” Other favorites
include defizzed Coke (Frank Shorter used to swear by it), which is a good source not only of
carbohydrate but of caffeine as well (the role of caffeine in preventing fatigue is discussed later).
Martin also points out that nonworking muscles cannot transfer their glycogen reserves to
working muscles; once glucose is inside a muscle cell, that’s where it stays until it’s
metabolized. “This might be one reason why many marathon runners prefer a race course with
periodic, slight elevation changes,” he says. “This allows the glycogen reserves to be shared
among a larger group of working muscles.” Runners who are racing on a very flat course might
consider occasionally varying their pace or stride length to mobilize unused glycogen stores.
Central Nervous System Fatigue
It should come as no surprise that the brain, as well as the muscles, can become fatigued over the
course of a marathon. In recent years, J. Mark Davis and others have begun to study the
relationship between changes in the central nervous system (the brain and spinal cord, or CNS)
and exercise-related fatigue.
Davis, a professor of exercise science and the director of the exercise biochemistry laboratory at
the University of South Carolina, suspects that CNS fatigue, the result of neurochemical changes
in the brain, is very likely to be involved in a runner hitting The Wall during a marathon. In fact,
he says, “I think that CNS fatigue is actually what causes most people to stop, as opposed to
muscle specific fatigue.” Aside from very highly motivated runners, he says, most people don’t
really drive or push themselves to complete muscle failure.
Davis cautions that his research is still at the preliminary stage, but his data certainly support the
CNS fatigue hypothesis. During prolonged exercise, the brain’s production of the
neurotransmitter (a chemical that carries signals from one neuron, or brain cell, to another)
serotonin increases steadily; it peaked, in his animal treadmill studies, when the animals
collapsed from exhaustion. Elevated levels of serotonin have been implicated in feelings of
tiredness, sleepiness, and lethargy. (The folk remedy of drinking a glass of warm milk before
going to bed has a sound scientific basis: milk, as well as chocolate, is a good source of the
amino acid tryptophan, the precursor to serotonin.)
The rising levels of serotonin are caused by increased delivery of tryptophan to the brain. What’s
interesting, Davis says, is that the increase in free tryptophan in the blood is very much related to
the increase in free fatty acids in the blood. “While many people believe that the increase in free
fatty acids is very important to delaying fatigue in the muscle,” says Davis, “we think it has a
negative effect in terms of central fatigue.”
To make matters worse for the marathon runner, the brain’s production of dopamine (the
neurotransmitter responsible for generating feelings of excitement, reward, motivation, and
pleasure) begins to drop even as serotonin levels are rising.
Page 13
One experimental approach to preventing an increase in serotonin synthesis has been to give
subjects nutritional supplements that include something called branched chain amino acids
(leucine, isoleucine, and valine). Branched chain amino acids (BCAAs) compete with tryptophan
for space on the receptors that carry chemicals from the blood to the brain. Unfortunately, while
BCAAs do indeed lower the levels of tryptophan and, by extension, serotonin in the brain, they
don’t prevent CNS fatigue during exercise. Davis believes BCAAs’ failure to prevent CNS
fatigue is due to one of their side effects: an increase in the blood levels of ammonia, a brain and
muscle toxin.
The best strategy for delaying both muscle and CNS fatigue, Davis says, is tried and true: eating
or drinking carbohydrates. “It’s well known that carbohydrate feeding blunts the increase in free
fatty acids,” he says, which of course ends up blunting the increase in serotonin, “so
carbohydrates cannot only delay glycogen depletion, but they also delay central fatigue.” In
addition, brain function in general is highly dependent upon blood glucose, as anyone who tries
to calculate mile splits at mile 23 probably knows.
Davis is beginning to investigate nutritional approaches to prevent dopamine levels from
dropping, including the addition of tyrosine (the precursor to dopamine as well as
norepinephrine, a stress-related hormone similar to adrenaline) to sports drinks, but he cautioned
that there are not yet data showing that tyrosine supplements raise dopamine levels during
exercise or delay fatigue.
Runners have been using caffeine to help delay fatigue for years, the prevailing wisdom being
that the substance increases the blood level of free fatty acids available for metabolism. Recent
research by Davis and others, however, indicates that caffeine plays another, perhaps more
important role, in delaying fatigue by increasing the levels of dopamine in the brain.
Cognitive Strategies
Yogi Berra said that “Baseball is 90 percent mental; the other half is physical.” Berra’s famously
charming illogic aside, the same could probably be said about any sport. Charles A. Garfield, a
sports psychologist and coauthor of the book Peak Performance: Mental Training Techniques of
the World’s Greatest Athletes (Warner Books, 1985), maintains that 60 to 90 percent of success
in sports can be attributed to “mental factors and psychological mastery.”
Scant scientific research examines the relationship between mental strategies and hitting The
Wall per se, although a body of research dating back to the 1970s documents the relationship
between a runner’s thought processes and performance. Faster race times are generally
associated with what have come to be known as associative strategies—thinking about physical
sensations, such as breathing, muscle soreness, or blisters, and other race-related issues such as
pacing and competitive strategy. During competition, elite runners tend to use associative
thinking strategies almost exclusively.
Athletes who achieve their peak performance usually experience something that has come to be
known as “flow,” a concept introduced to the world in the 1970s by psychologist Mihaly
Csikszentmihalyi. Flow is “a state of consciousness where one becomes totally absorbed in what
Page 14
one is doing, to the exclusion of all other thoughts and emotions,” according to Susan A. Jackson
and Csikszentmihalyi, authors of Flow in Sports (Human Kinetics, 1999). “So flow is about
focus.” In other words, when you experience that running nirvana during which everything
seems effortless, you are probably thinking associatively.
Unfortunately, most of us are not able to maintain a state of flow for an entire marathon. Slower
runners tend to use dissociative strategies—thinking about things not directly related to the
race—in addition to associative strategies.
“There is some reason to believe that people with different levels of running experience may
benefit more from using different strategies,” says Britton Brewer, associate professor of
psychology at Springfield College in Springfield, Massachusetts. “People who are more
experienced in the sport may be able to make better use of associative strategies, because they
won’t be intimidated or panicky when they experience various symptoms that they encounter
while distance running.”
Kevin Masters, associate professor of psychology at Utah State University, agrees, even
suggesting that average runners should learn ways to distract themselves during the marathon.
“The overwhelming evidence shows that [distracting yourself mentally makes] time seem to go
faster, and you feel that you are exerting less energy. Overall you will run a little bit slower, but
for most people that’s not a big issue.”
A 1998 study by Clare D. Stevinson and Stuart J.H. Biddle, published in the British Journal of
Sports Medicine, made a further distinction in marathon runners’ mental strategies, describing
four types of thinking used by nonelite runners in the 1996 London Marathon.
The first type was internal association, or focusing on how the body feels while running. The
second type of thinking was external association, in which the runner’s attention is focused
outwardly on things important to the race: calculating split times, negotiating water stations, or
jockeying for position with competitors. The third mode of thinking was inward dissociation (or
distraction): daydreaming, singing silently (or aloud!), or solving mental puzzles. Runners who
used the fourth mental strategy, external association, tended to focus their attention outwardly on
events unimportant to race performance: the scenery, the cheering crowds, other runners dressed
in kooky outfits.
The researchers found that the most prevalent mental strategy for all runners, whether they hit
The Wall or not, was inward association. But those runners who reported hitting The Wall
tended to use inward dissociation much more frequently than their wall-avoiding competitors.
The authors speculate that “It is likely that being distracted from sensory signals and important
aspects of the task meant that runners were not able to judge their pace very well and failed to
stay fully hydrated, contributing greatly to ‘hitting The Wall.’ ”
While it might seem plausible that external dissociation might lead runners into a similar trap,
the authors found this not to be the case, possibly because “noticing spectators, aspects of the
scenery, or, in particular, other runners, made runners inadvertently aware of the speed at which
they were running as they passed by them or were overtaken.”
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On the other hand, the researchers suggest that paying too much attention to the body (inward
association) made their subjects magnify their discomfort, making The Wall seem to appear
much earlier and for a longer period of time. Their advice: make brief but regular checks on your
body, rather than constantly monitoring every step of the race. Focus most of your attention
externally: be aware of critical race-related factors and enjoy the atmosphere of the race.
Do Women Have an Advantage on the Long Haul?
Stevinson and Biddle found that men were significantly more likely to report hitting The Wall
than women—a statistic that should be interpreted with some caution, as women represented
only 15 percent of their sample population. Even so, it does provide support for the view that
women might be better suited to the demands of endurance running.
A body of research shows that women utilize proportionally more lipid and less carbohydrate
than men during low to moderately high intensity exercise. In addition, levels of epinephrine and
norepinephrine, hormones that (among other things) stimulate glycogen mobilization, rise
significantly more in men than in women during exercise. These sex differences in fuel
metabolism have led some scientists to speculate that men might deplete their glycogen stores
more rapidly than women. In theory, yes, according to Tracy Horton of the Center for Human
Nutrition at the University of Colorado Health Sciences Center in Denver. In practice, probably
not.
“I would say that if they didn’t eat before or during the race, men would probably hit The Wall
sooner,” said Horton. “But most people eat before racing and take some form of fuel replacement
during a race. In that case, the women’s advantage is probably negated. Even eating just an hour
before the race can provide an alternative energy source to the body’s stores of glycogen. I
would say that in most cases, there is probably not going to be that much difference.”
Stevinson and Biddle speculate that women might also be better at judging pace or that they
simply trained more for the marathon, leading one reader to respond that he had noticed many
men seem to be motivated “more out of bravado than as a result of solid training.” Speculation,
to be sure, but food for thought nonetheless.
What NOT To Do: a Cautionary Tale
Dick Beardsley’s race strategy for the second marathon of his life—the one in which an elephant
jumped on his shoulders—is a classic primer on how not to prepare for and run a marathon. He
had run his first marathon on a whim when he was in junior college and finished in 2:47:14. Not
too bad, especially considering that he hadn’t trained for the marathon distance. Two months
later he learned of a marathon in nearby Minneapolis. It was Tuesday, and the marathon was on
Sunday. He decided to “prepare” himself for this one. Relying upon advice in an article he found
in an old running magazine, he decided to fast until the marathon, allowing himself only
Gatorade, juice, and water.
On the morning of the marathon, he put on his brand-new pair of running shoes and went out for
an eight-mile warm-up. He went out fast in the first few miles of the marathon. He bypassed the
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aid stations—didn’t everyone know that drinking anything during a race would give you a side
ache?
Beardsley was still feeling pretty good, despite the blisters on his feet, as he ran past the 20-mile
mark where someone had painted the words, “You’re at The Wall.” And then, just past mile 23,
he felt like a sledgehammer had come down on him. “I went from feeling pretty good to where I
did not know how I was going to get to the next telephone pole,” he said. “I was running with my
eyes shut, hallucinating. Without a doubt, that was the worst wall I ever hit.” He collapsed at the
finish line, severely dehydrated.
It’s a testament to Beardsley’s superb physical abilities and mental toughness that he managed to
finish the race, much less to finish seventh overall.
Mistake number one: by fasting the week before the race, he probably started off in a state of
near-glycogen depletion.
Mistake number two: running in a brand-new pair of running shoes. It is difficult to maintain
your cognitive focus on race-related issues as you are developing painful blisters. His eight-mile
warm-up was about seven and a half miles too long. By going out too fast, he probably incurred
some lactic acid buildup, which lessened the amount of glucose that he could metabolize later
on. Not eating or drinking during the race was a recipe for glycogen depletion and dehydration.
Beardsley, of course, learned his lesson well, going on to become one of the best marathoners in
the United States and making history in his memorable finish two seconds behind Alberto
Salazar in the 1982 Boston Marathon.
References
Beardsley, D., & Anderson, M. (2002). Staying the Course: A Runner’s Toughest Race.
Minneapolis: University of Minnesota Press.
Braun, B., & Horton, T. (2001). Endocrine regulation of exercise substrate utilization in women
compared to men. Exercise and Sport Science Reviews, 29(4), 149-154.
Davis, J.M., & Bailey, S.P. (1997). Possible mechanisms of central nervous system fatigue
during exercise. Medicine and Science in Sports and Exercise, 29(1), 45-57.
Garfield, C.A., with Bennett, H.Z. (1985). Peak Performance: Mental Training Techniques of the
World’s Greatest Athletes. New York: Warner Books.
Martin, D.E., & Coe, P.N. (1997). Better Training for Distance Runners. 2nd ed. Champaign, Ill.:
Human Kinetics.
Masters, K.S., & Ogles, B.M. (1998). Associative and dissociative cognitive strategies in
exercise and running: 20 years later, what do we know? The Sport Psychologist, 12:253-270.
Page 17
Stevinson, C.D., & Biddle, S.J.H. (1998). Cognitive orientations in marathon running and
‘hitting the wall.’ British Journal of Sports Medicine, 32:229-235.
This article originally appeared in the September/October 2003 issue of Marathon & Beyond.
For information about reprinting or excerpting this article or any other M&B article, contact Jan
Seeley via email or at 217-359-9345.
Page 18
Pre survey questions Energy Transfer & Metabolism
The following questions are designed to determine your knowledge of Energy transfer and
Metabolism prior to this unit in Bio375. Please answer honestly. These will be evaluated only
for completeness.
1. Rate your understanding of these topics:
1 = I have never heard of this topic
2 = I have heard of this topic, but I am unsure what it is or how it relates to Energy Transfer &
Metabolism
3 = I understand this topic, but am unsure how it relates to Energy Transfer & Metabolism
4 = I understand this topic and how it applies to Energy Transfer & Metabolism
5 = I understand this topic, how it applies to Energy Transfer & Metabolism, and am able to
apply knowledge of this topic in other contexts. * If you choose #5, please explain how you
would apply your knowledge to other contexts
Cells are not at equilibrium and require energy input to maintain homeostasis
Energy is stored as glycogen & fats
The different steps in metabolism
Glycogen as a fuel source
Fatty acids as a fuel source
ATP hydrolysis
ATP synthesis
2. Rate your ability to answer the following questions
1 = I am not confident in my ability to answer this question.
2 = I am somewhat confident in my ability to answer this question.
3 = I am very confident in my ability to answer this question.
Question 1 (Blooms Level (BL) 1):
ATP stores energy in:
a) High energy phosphate bonds
b) High energy carbon bonds
c) High energy oxygen bonds
Question 2 (BL 2):
When we say that something give us “energy”, what does that mean? What is a biological definition of
energy?
Answer: describe/explain this
Question 3 (BL 3):
Page 19
In the morning you wake up hungry. While you were sleeping (fasting), your brain continued to use
glucose for energy. As a result, your blood glucose levels drop steadily. When they reach a specific
threshold, your brain releases a hormone signaling for the synthesis of glucose. What happens next?
Use the following strip sequence to order the following metabolic steps
Glucose monomers are released into the blood from the digestive system
Glucose in the blood is absorbed by the liver and muscles
Glucose is absorbed by the brain
You consume a gigantic bowl of oatmeal (rich in carbs), which is digested and
converted into glucose monomers
Glucose goes through glycolysis for the synthesis of ATP
Glucose is used for fatty acid synthesis
Glucose is converted to glycogen for immediate storage
Question 4 (BL 4):
Compare molecule A and molecule B.
Molecule A:
O
O
O
O
O
O
Molecule B:
Page 20
a) Which molecule will provide more energy in the form of ATP?
b) Which molecule is metabolized faster?
Question 5 (BL 5 & 6):
You are at the UW SURF and just spent 2 hours working out with your best friend (your new record!).
By the end of your workout you are exhausted and ready to go eat a burger at Dotty’s. Please answer the
following questions:
a) During your workout you feel great for the first 45 minutes, and then start to really struggle.
However, your roommate feels fine at 45 minutes and doesn’t begin to struggle until 1.5 hrs in.
Please explain in the context of metabolism why this happened.
Answer:
b) How will the burger you eat at Dotty’s replenish your energy stock? Please talk about the roles of
carbohydrate, fatty acids, and amino acids in metabolism.
Answer:
Question 6 (BL 6): Evaluate the merit of the following argument
Argument: Caffeine (cup of coffee, energy drink) should be taken before exercising because it
will give you more energy.
Structure of caffeine (C8H10N402)
Page 21
Within your evaluation please address the following topics:
Does caffeine provide energy? If it does, explain how. If it doesn’t, in what ways might caffeine
provide the perception of increased energy after consumption?
Page 22
Exam questions
1. (2pts)
ATP stores energy in:
a) High energy phosphate bonds
b) High energy carbon bonds
c) High energy oxygen bonds
2. (3pts):
In the morning you wake up hungry. While you were sleeping (fasting), your brain continued to use
glucose for energy. As a result, your blood glucose level dropped steadily. When the blood glucose
level reaches a specific threshold, your brain releases a hormone signaling for the synthesis of
glucose. What happens next? Use the following strip sequence to order the following metabolic
steps:
Glucose is absorbed by the brain
Glucose is used for fatty acid synthesis
Glucose monomers are released into the blood from the digestive system,
increasing the blood glucose level
You consume a gigantic bowl of oatmeal (rich in carbs), which is digested and
converted into glucose monomers
The brain uses glucose for the synthesis of ATP
Excess glucose in the blood is absorbed by the liver and muscles
Glucose is converted to glycogen for immediate storage
Page 23
For questions 3 & 4, compare molecule A and molecule B:
Molecule A:
Molecule B:
3. (1 pt.) Which molecule will provide more energy in the form of ATP?
A) molecule A
B) Molecule B
4. (1 pt.) Which molecule ALWAYS requires oxygen for its breakdown?
a) molecule A
b) molecule B
5. (6pts): You are at the UW SERF and just spent 2 hours working out with your best friend (your
new record!). By the end of your workout you are exhausted and ready to go eat a burger at
Dotty’s. Please answer the following questions:
A) During your workout you feel great for the first 45 minutes, and then start to really
struggle. However, your roommate feels fine at 45 minutes and doesn’t begin to struggle until 1.5
hrs. in. In the space provided, please explain in the context of metabolism why this happened.
B) How will the burger you eat at Dotty’s replenish your energy stock? In the space
provided, please talk about the roles of carbohydrate, fatty acids, and amino acids in exercise
metabolism.
Page 24
6. (4pts): Evaluate the merit of the following argument in ~100 words.
Argument: Caffeine should be taken before exercising because it will give you more energy.
Structure of caffeine (C8H10N402)
Within your evaluation please address the following topics: Does caffeine provide energy? If it
does, explain how. If it doesn’t, why might someone think it does?
7. (2pts): What effects does increased training have on fuel utilization? (Select all that are TRUE)
A) It increases the amount of energy we store as fat
B) It increases the amount of energy we store as glycogen
C) It increases the amount of glycogen used during exercise
D) It increases the amount of oxygen delivered to muscles
E) It increases the utilization of fat for ATP synthesis
Page 25
8. (1pt) Rate your confidence in answering the 7 metabolism questions
1 = I am not confident in my ability to answer this question.
2 = I am somewhat confident in my ability to answer this question.
3 = I am very confident in my ability to answer this question.
A. Question 6
B. Question 7
C. Question 8
D. Question 9
E. Question 10
F. Question 11
9. Rate your understanding of these topics:
1 = I have never heard of this topic
2 = I have heard of this topic, but I am unsure what it is or how it relates to Energy Transfer &
Metabolism
3 = I understand this topic, but am unsure how it relates to Energy Transfer & Metabolism
4 = I understand this topic and how it applies to Energy Transfer & Metabolism
5 = I understand this topic, how it applies to Energy Transfer & Metabolism, and am able to
apply knowledge of this topic in other contexts. * If you choose #5, please explain how you
would apply your knowledge to other contexts
Cells are not at equilibrium and require energy input to maintain homeostasis
Energy is stored as glycogen & fats
The different steps in metabolism
Glycogen as a fuel source
Fatty acids as a fuel source
ATP hydrolysis
ATP synthesis
Page 26
Transcripts for the Videos
Episode 41 transcript http://www.interactive-biology.com/2012/an-introduction-to-skeletalmuscle-contraction/
Transcript of Today’s Episode
{Video begins with Leslie in a gym doing some sets of bicep curls} Oh, hey! Hello and welcome
to another episode of Interactive Biology TV where we’re making Biology fun. My name is
Leslie Samuel and in this episode, Episode 41, I’m going to give you an introduction to skeletal
muscle contraction. But, one second. Let me finish my set. {Leslie goes back to finish a few
more sets of his bicep curls.}
So, here I am working out in the gym and I am doing some bicep curls. I’m lifting the weight and
there’s muscle contraction happening. Now, when I’m talking about skeletal muscle, I’m talking
about this voluntary muscle. The muscle that I have control over and it’s the ones that I use to
move my bones, to move my body, to walk, to lift weights, and as you can see here, I am doing
some bicep curls. I am using my biceps.
Now, let’s look over here to the right. You will see that the biceps are these muscles over here.
And, what I’m actually doing is I’m contracting these muscles, making these muscle fibers
shorter, and as they become shorter, they are actually pulling my arm up in that direction. So,
I’m making these muscles shorter by contracting them and that is pulling on the bones in my
arms, my lower arms and that is raising my lower arms.
Now, you can see here that there are a lot of stripes. We call these stripes, striations. And, each
individual fiber that you see here is one muscle cell. So, these cells are narrow but, they are also
very long. So, these are the muscle cells and you can see they are many muscle cells that make
up each muscle and each muscle group.
Now, what we are going to do is we are going to take one of these muscle fibers and look at
what’s happening there. So, let’s go to the next slide.
Here we have one muscle fiber and, you can see we have an axon coming in. So, the axon here is
number one and that axon makes a synaptic connection with this muscle cell or another thing you
can call it is a muscle fiber. And the interesting thing about this muscle fiber is that it’s made up
of these tubes that kind of go all the way along, kind of like little fibers inside the muscle fiber
and those are called myofibrils. So, we have the muscle fiber or the muscle cell which can be
very long and very slender and narrow. We have the axon that is coming in making a synaptic
connection with the muscle cell and these little fibrils, myofibrils inside of the muscle cell. This
entire thing with the neuron, the motor neuron and the muscle cell, this is called a neuromuscular
junction. In other words, it’s the junction or the connection between the nervous system and the
muscle cells.
Now, what I’m going to do is I’m going to take one of these myofibrils, these guys in here and I
am going to look at that down here. So, let’s go ahead and do that. And, this is going to look a
Page 27
little strange but, what I’m basically doing, this is one fiber. All of these here, it actually extends
much longer than that. This is looking at one of these fibers. And you’re going to see that there
are these different sections, and it goes from here to here, and then, from here to here. We’re
going to talk about what these different components are and what role they play in muscle
contraction.
Now, right here, each one of these units, I call a sarcomere. The sarcomere, this important unit
here is the functional unit of contraction. This is really where the contraction happens. The
sarcomere is made up of two main fibers. The main fibers are actin, and this narrow one here,
I’m going to call actin; and the thicker fiber is called myosin. So, we have actin filaments and
myosin filaments. So, we have actin and we have myosin.
And what’s happening as I contract my muscles is that on the myosin we actually have these
little heads that extend and, you know what I’m just going to zoom in on one of those heads and
you can see that over here. We have the myosin head here and it’s connecting to the actin and
what that does when contraction is supposed to happen, this actually moves and pulls against the
actin. So, you can imagine here. You have these little heads that are pulling, pulling in this
direction, and what ends up happening is, this distance here shortens as this moves in and this
moves in because of the heads that are pulling on it.
So, once again up here you have the myosin head that’s moving in this direction. As it moves in
that direction, it pulls the actin along, and that pulling shortens the sarcomere so that you might
have maybe the sarcomere being this long instead of that long. So, it’s shortening it. And, what
that’s going to do, it doesn’t only happen here, it happens here, it happens here, it happens here
all along the muscle fiber or the muscle cell, that shortens the muscle and that causes contraction.
All right so, we’re just kind of going over the major details that are happening. In future
episodes, we are actually going to look at these individual steps and break them down a little
more. But, for right now, that’s just an introduction into muscle contraction, specifically, skeletal
muscle contraction.
That’s it for this video. If you have any questions, you can leave them in the comments and you
can always visit the website at interactive-biology.com for more Biology videos and other
resources. That’s it for now, and I’ll see you on the next one.
[/spoiler]
Episode 42 transcript http://www.interactive-biology.com/2032/how-the-release-of-calciumions-results-in-muscle-contraction-episode-42/
Hello and welcome to another episode of Interactive Biology TV where we’re making Biology
fun! My name is Leslie Samuel and in this episode, Episode 42, I am going to talk about how the
release of calcium ions results in muscle contraction. So, let’s get right into it.
So, here we’re looking at a muscle and there are a few terms that I want you to know. This is
called the fascicle, so this section right here, that’s a fascicle and that is basically a bundle of
muscle cells. And, this of course then would be individual muscle cells or, as I said in the last
Page 28
episode, you can also call it muscle fibers. What I’m going to do now, is we’re going to take this
muscle cell and we’re going to look at it much larger here. Here you can see we have the muscle
cell, the muscle fiber and that is made up of these individual myofibrils. So, this would be a
myofibril.
We looked at the myofibril in the previous episode and we showed how they’re made up of
sarcomeres and I’m going to call a sarcomere from right here, you see this part here, to here, that
is one sarcomere. As I said in the previous episode, this is the functional unit of contraction.
We’re going to look at how calcium ions is responsible for the contraction of this sarcomere.
And, we’re going to look at an animation of how that contraction looks.
So, let’s go to the next slide. Here, we’re looking at the sarcomere and we looked at the parts of
the sarcomere. We said that we had a thick filament and that thick filament was myosin, and then
we had a thin filament, and that thin filament is called actin.
Now, when muscle contraction happens, it’s because of the sarcomere becoming shorter, this is
moving in and I’m going to animate that for you. This is contraction happening, and then the
muscle relaxes and it goes back to how it was before. Contraction happens, the muscle relaxes,
and then it goes back to how it was before. To put that in perspective, this is me working out in
the gym, and as I contract the muscles in my arms, this is what happens. So, my bicep muscles
contract, I pull it up, you can see it shortening. The sarcomere is getting shorter. We looked a
little bit at how that happens. We said that there are myosin heads on the myosin that actually
pulls along and pulls the actin so that this entire unit gets shorter. As the sarcomeres get shorter,
and you have many of them along the myofibrils, as they get shorter, the muscle contracts and
that causes my lower arm to move up in that direction.
So, now let’s take that and look at a little more detail. So, we’re going back to this picture where
we’re looking at the muscle fiber so, that’s this part here again, and as we look at the muscle
fiber, there’s something that I want you to notice. Here, we have the membrane that surrounds
the muscle fiber and that membrane, we’re going to call that the sarcolemma. Now, you’re
probably noticing that I’m using this prefix sarco- a lot. That prefix sarco- refers to the muscle.
So, the sarcolemma, the sarcomere… anytime you hear sarco-, you can assume that we’re talking
about something relating to muscle. The interesting thing about the sarcolemma is that you have
these little openings where the membrane actually goes deep into the cell. And you can see it
coming here and you can see it going through there. Where the membrane goes deep into the
cell, that is called T-tubules. So, they’re basically these little tubes that go deep into the cell. And
they serve a very important purpose. This is how it works.
Last time we looked at the fact that axons come in and make synaptic connections with the
muscle cells. This is called the neuromuscular junction. So, when a signal comes down, and it
releases the neurotransmitter, in this case the neurotransmitter is acetylcholine, and releases that
neurotransmitter, it binds to the receptors that causes the signal in the muscle cell membrane, in
the sarcolemma. That signal then travels deep into the cell via these T-tubules and something
very important happens. Now, you can see that it looks like it’s one tube that’s going down deep
into the cell. But, that tube, I’m going to take that and draw it over here and it’s not by itself. So,
Page 29
here we have the T-tubule and then surrounding the T-tubules, next to the T-tubules, we have the
sarcoplasmic reticulum. So, I’m going to draw those here and it’s just going to look like tubes
coming down next to the T-tubule. It’s not shown here but, I’m going to show that over here.
And, as I said that is called the sarcoplasmic reticulum. The sarcoplasmic reticulum stores
calcium ions. So, we have calcium ions inside the sarcoplasmic reticulum. So, let me illustrate
that here so, Ca2+, Ca2+, and that’s all throughout the sarcoplasmic reticulum, it’s being stored
there for when it needs to be used.
So, once again, we have a signal that’s coming down the axon causing a signal in the
sarcolemma. That signal then goes deep into the muscle via the T-tubules. On the T-tubules, we
have a receptor that we call the dihydropyridine receptor and on the sarcoplasmic reticulum, we
have a receptor that we call the ryanodine receptor. So, let me write those over here. The red is
the dihydropyridine receptor (hopefully, I‘m spelling this right) and here we have in blue, the
ryanodine receptor. All right, so we have our signal, the signal comes along the sarcolemma, that
signal spreads deep into the muscle cell via the T-tubules, that’s going to cause the
dihydropyridine receptor to interact with the ryanodine receptor, that it opens the channel and let
calcium ions flow out into the cell. Okay so, calcium is flowing out into the cell, out of the
sarcoplasmic reticulum, and when that calcium flows out, that then causes muscle contraction.
I’m not going to go through all the details as to how it causes muscle contraction in this video
but, I’m going to do that in the next episode.
The take-home message is, the signal comes via the axon, causes a signal in the sarcolemma, that
signal travels deep into the muscle cell via the T-tubles. Because of the relationship between the
dihydropyridine receptor and the ryanodine receptor, that causes calcium that is stored in the
sarcoplasmic reticulum to be released, and the calcium released then causes muscle contraction.
So, we can look at it here again and we can see here, this is where calcium is being released, and
then the calcium is then pumped back out, calcium is being released, calcium is pumped back
out.
Now, there’s one thing I didn’t mention and that’s the second part with calcium being pumped
back out. You have the T-tubule, you have the sarcoplasmic reticulum, and in the membrane of
the sarcoplasmic reticulum, you also have calcium pumps and once the signal is over, the
calcium pumps pump the calcium right back into the sarcoplasmic reticulum. So, that’s what’s
happening here, calcium being released, calcium being pumped back in, calcium being released,
calcium being pumped back in.
That’s all the content for this video. If you have any questions, of course you can ask them in the
comments section below, and as usual, you can visit the website at interactive-biology.com for
more Biology videos and other resources. That’s it for this video and I’ll see you on the next one.
Episode 43 transcript http://www.interactive-biology.com/2133/043-the-details-of-musclecontraction/
Transcript of Today’s Episode
Page 30
Hello and welcome to another episode of Interactive Biology TV where we’re making Biology
fun! My name is Leslie Samuel and in this episode, Episode 43, I am going to go into the details
of muscle contraction. This is going to be the last video in the muscle contraction series, so,
enjoy! Let’s get right into it.
You can always go back to Episode 42 to refresh your memory but, we said that the functional
unit of contraction is called the sarcomere and, that is what we’re looking at right now. This unit
is one sarcomere. We said that we have a thick filament that is called myosin and, we have a thin
filament that is called actin. We said that, when muscle contraction happens, the more the neuron
releases neurotransmitter that stimulates calcium release. When that happens, the fibers slide
against each other just like this. So, as the muscle fibers becomes shorter, that is the muscle
contracting. And you can clearly see that in this animation.
The reason we said that this can happen is because on the myosin filaments, we have these heads
and those heads extend and bind to the actin. When they bind, they kind of flex so, it moves in
this direction and that pulls the actin shortening the sarcomere.
What we are going to do today is we’re going to look at the details of what is happening there.
We are going to look at six steps in muscle contraction. This is another image that’s showing
something similar to what we’ve looked at. We have the myosin heads. Let me do that in a
different color so that you can make sure to see it because we have a lot of red there. We have
the myosin heads that are binding to the actin filaments.
Here, we are going to be looking at that in more details. We have the actin. Yes, it’s a different
spelling because it’s from a different language but, on the actin filaments, there are two things
that are very important. We have tropomyosin as you see here so that’s this long strand here. On
top of the tropomyosin, we have troponin. This is a complex that we find all along the actin
filaments.
Here’s the situation. Because this is here, the myosin heads want to bind to the actin. There’s
some binding sites on the actin so, let’s say this is a binding site right here. But, what’s the
problem? The tropomyosin is covering that binding site so, the myosin heads cannot bind. Okay,
so, we have these myosin head-binding sites all along the actin; myosin heads want to bind, we
have all these myosin heads ready to do their business but, they cannot because it’s blocked by
the tropomyosin.
All right so, let’s go now and look at the six steps of muscle contraction. Step number one.
Calcium is released from the terminal cisternae. Remember we said that the terminal cisternae is
a part of the sarcoplasmic reticulum and that is where calcium is stored. So, calcium is released.
You can see here, we have this little binding site for the calcium so the calcium now comes and
binds the troponin. So, here we have calcium and binding to the troponin. And then, what that
does is it causes a conformational change. To put it more simply, we’re just moving the
tropomyosin-troponin complex. So, that moves and, when that moves, it exposes the binding
sites on the actin. That’s step number one. So, step number one: We had calcium in the terminal
cisternae that is released when there’s a stimulus. The calcium ions bind to the troponin causing
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a conformational change in the troponin-tropomyosin complex. In other words, it’s moving out
of the way. And then, the next step can happen. That step is, the myosin heads can bind to the
binding sites on the actin. So, this is the one binding site. For simplification we’re just showing
one myosin head but, as you know we have many myosin heads all along this actin.
In order for that to happen, we said that there’s normally ATP that’s on the myosin heads and
you saw that, you saw that in the previous figure. But, that ATP has to be hydrolyzed to become
ADP and an inorganic phosphate (Pi). So, we have ADP and the phosphate. All right, so, we
have the myosin head that has bound to the binding site on the actin. That was step number two.
Step number three. This ADP and Pi is released from the myosin head. I’m not showing that in
the figure but, just imagine that being released. When that is released it causes the power stroke.
In other words, it causes this guy here to flex. And when it flexes, it moves in this direction and
that causes the actin to slide across the myosin.
Okay, so, calcium is released, step number one, binds to the troponin, causes this change in the
troponin-tropomyosin complex so that it gets out of the way; ATP being hydrolyzed into ADP
and inorganic phosphate is a state that this needs to be in for the myosin head to bind. When
those are released, the myosin head flexes and we get the power stroke. That’s step number
three.
Let’s go to step number four. Step number four is another one that I’m not showing but, we have
ATP. So, this is an ATP molecule that comes in and binds to the myosin head. When that binds
to the myosin head, the myosin head then detaches from the actin so, we no longer have that
connection. That’s step number four.
Step number five. ATP is hydrolyzed which re-energizes the myosin head. So, once we have
ATP being hydrolyzed like it is here, that re-energizes the myosin head and it’s ready to go
again.
One more step, step number six. This calcium here needs to be gone. So, we have the terminal
cisternae and it’s not shown here. So, I’m just going to draw it with my great artistic skills. We
have calcium pumps in the terminal cisternae. What that does is it basically pumps that calcium
back in. So, we have calcium being pumped back in that is going to cause the troponintropomyosin complex to go back to where it was and it’s going to be blocking… I should have
done that in green to keep the consistency. Oh, I still can, why not. Okay, so we have the
troponin-tropomyosin complex that is blocking once again the binding site for the myosin head.
All right, so let’s recap on that real quick. Step number one: Calcium is released, binds to the
troponin. When it binds, it causes a conformational change or a shift, whichever one you want to
call it, it causes that shift exposing the binding sites on the actin. Step number two: Myosin head
binds to the actin. Remember that the ATP has to be hydrolyzed into ADP and Pi in order for
that to take place, it has to be re-energized. It gets that from that hydrolysis process. Step number
three: ADP and Pi release that causes power strokes that causes this guy to flex. Then, ATP
comes in, binds to the myosin head, causes the myosin head to be released from the actin. The
Page 32
myosin head gets re-energized when the ATP is hydrolyzed back into ADP and Pi. Calcium ions
are pumped back into the terminal cisternae and this process can happen again.
Well, that’s pretty much it. That is muscle contraction. If you have any questions, go ahead and
leave them in the comments. That’s all for this video, and I’ll see you on the
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Case study documents:
Each case was adapted from: “A Can of Bull?” by Heidemann & Urquhart, National
Center for Case Study Teaching in Science
http://sciencecases.lib.buffalo.edu/cs/files/energy_drinks.pdf
Acknowledgement: I would like to acknowledge Merle Heidemann (division of Science and
Mathematics Education) and Gerald Urquhart (Lyman Briggs School of Science) from Michigan
State University who original developed and published this case study(A Can of Bull, Do Energy
Drinks Really Provide a Source of Energy?) in 2005 at the NSF sponsored National Center for
Case Study Teaching in Science.
Description of modifications:
The case was modified to have students examine the impact of energy products on someone who
is racing a marathon. Four versions of the case were created based on the same learning
objectives and outcomes. The only differences are related to plan and supplements each runner
chose. Further, the biochemical information provided to the students only included what was
relevant to each case. Having multiple versions of the case allowed students exposure to
multiple products even though in small groups they only investigated the supplement plan of one
runner.
Case Study title: A Can of Bull? Do Energy Drinks, Bars, and Gels Really Provide a
Source of Energy? Can that Energy be used During a Marathon?
Adapted from: “A Can of Bull?” by Heidemann & Urquhart, National
Center for Case Study Teaching in Science
Learning Goals/Objectives




You will understand what determines if something gives you energy
You will understand how energy is stored for long term us in the body
You will understand how energy is used during endurance exercise
You will understand which stores of energy are used at different times
The Case
You are a writer for Runners’ World magazine. In one of your most popular columns,
Marathon Master, you recently solicited your readers for their race strategies to avoid hitting
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“the wall”. Several of them replied citing specific supplements they plan on using. For your
next assignment, you need to find out what each of the ingredients in these supplements are
and what it does for the runner. You need to be very accurate in your analysis- determine
what each component really does for the body, not what the marketers want you to believe it
does. Many of your readers are using these supplements with the general notion that they’re
helpful, but they’re basing their use of them on no scientific information. After seeing the
responses your readers provided, you have been provided with the marketing claims, a list of
ingredients and nutrition facts provided on the products for consumers. Using a short list of
questions, formulate an appropriate response to your assigned reader (each group has 1
runner to respond to). You will need to evaluate their race nutrition strategy and offer advice
to how this plan may help or hinder their performance in the context of metabolism.
Fall Marathon Season Approaches: Are you Ready?
Dear Readers,
That time of year is again upon us. Late September to early October- Fall marathon
season! Many of you have diligently been following your training plans, eating well,
and doing everything you can to prevent injury. However, if you are like me, even
with all of our preparation we still seem to get caught up in prerace fears. “The Wall”
seems like an insurmountable obstacle that could leave us with a full-body mutiny
mid race.
“The Wall” It evades easy definition, but to borrow from Supreme Court
Justice Potter Stewart’s famous definition of obscenity, you know it when you
see it—or rather, hit it. It usually happens around mile 20, give or take a
couple of miles. Your pace slows, sometimes considerably. Some runners say
that it feels as though their legs had been filled with lead quail shot, like the
stomach of Mark Twain’s unfortunate jumping frog of Calaveras County.
Others can’t feel their feet at all. Thought processes become a little fuzzy.
(“Mile 22, again? I thought I just passed mile 22!”) Muscle coordination goes
out the window, and self-doubt casts a deep shadow over the soul.
The bad news is that more than half of all non-elite marathon runners report
having hit The Wall at least once. The good news is that more than 40 percent
of all non-elite marathon runners have never hit The Wall. In other words,
while it certainly doesn’t hurt to be prepared for the possibility of hitting The
Wall, doing so is far from inevitable.
An excerpt from “Hitting the Wall”, by Sara Latta
Reprinted, with permission, from Marathon & Beyond
(www.marathonandbeyond.com)
My question to you is, with this possibility, what is your plan to avoid hitting the
wall? As an expert on energy metabolism, I will evaluate your strategy and offer
advice to how this plan may help or hinder your performance in the context of
metabolism.
All the best,
Marathon Master
Reader Responses:
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Runner 1
Dear Marathon Master,
I am so glad you asked! I am getting ready for my second marathon, Chicago 2011, and
am really worried about hitting the wall. I ran my first marathon last fall, the Milwaukee
Lakefront Marathon. During that race everything was going fine until mile 20. I had run
even splits, taken water during the water stops, and consumed a PowerBar gel every 7
miles. However, at 20 miles I went from feeling fine to feeling like my legs were dead
weights. The last 10k was the absolute worst I have ever felt while running. All I could
think about was that if I stopped, there would be no way I would EVER be able to start
moving again. I was so out of it I even accidentally threw my cup full of Gatorade onto a
volunteer at mile 25! How embarrassing!
Anyway, I want to make sure this doesn’t happen again. I started training earlier this
year (4 months out instead of 3) and am feeling really strong. For my race, I plan to take
a PowerBar gel every 7 miles (like last time), but also take in Gatorade and water at
alternating aid stations. Do you think this is a good idea? I know that I hit the wall last
time even while taking in supplements, but I don’t really think the PowerBar gels would
have negatively impacted my performance (at least that is what it says on the package!).
Go me!
ITGV (I Threw Gatorade at a Volunteer!)
Products to investigate: PowerBar gel, Gatorade
Runner 2
Dear Marathon Master,
I am planning on running the Salt Lake City Marathon this year. I’ve been doing lots of
training (80+ mi weeks) and am excited for the race. It will be my 4th marathon and I am
going for a personal best. Given your excellent understanding of metabolism, I was
wondering if I could share my fueling plan with you for feedback.
My plan
1. Wake up early and eat half a can of Pringles (whole grain), 1 bagel, 1/4 of a Gatorade
and half a cup of nuts. I try to do this all about 3-4 hours before the start.
2. I will take a GU 45 minutes before the start.
3. I will take a GU on the starting line and then carry two more with me.
4. During the race I alternate between water and Gatorade. I only try to take a few sips of
Gatorade.
5. Gu it up at mile 7!
6. Emergency Gu at mile 17 if I'm not feeling sick. I will start to take Gatorade every
mile at this point.
1.
Since steps 1, 2, and 3 all take place before I am running, I consider these my
energy rich breakfast (full of carbohydrates (Pringles, bagel) and fats (nuts). I have had
this for breakfast for my last few races and it has worked really well, I haven’t hit the
wall once. What I am wondering is whether or not the GUs will be useful to me during
the race. Also, I’ve taken Gatorade before, but don’t know if it is really helping.
Looking forward to hearing from you,
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SLC bound
Products to investigate: GU, Gatorade
Runner 3
Dear Marathon Master,
I ran my first marathon in 2008 at the San Francisco Marathon, and it was a terrible
affair. I was coming off a solid college track season and decided to do a three month
buildup of marathon work from 5k track racing and try my hand at the 26.2 distance. I
did no specific training just easy runs and long runs, however about a month out from the
race I got food poisoning and was out for 10 days. As a result my longest run going into
the race was 14 miles. I started conservatively as one of my goals was to go under 3
hours, but I got excited and went through 20 miles in 2:06 (6:19/mi) and finished the full
26.2 in 2:48. The last 10km was terrible as I averaged 6:45 and was using the entire road;
I ended up in the medical tent as I was unable to maintain my core body temperature and
remained there for 30 minutes. I know I was properly hydrated as I had to pee really
badly (and did) at mile 23 and it was of appropriate color (light yellow). Temperatures
were in the high 40’s low 50’s the entire race.
Here was my fueling strategy:
Breakfast 1.5 hours before, toast with nutella + 8 oz of earl grey tea.
15 minutes before 1 GU w/ 12oz Gatorade
8 oz of Gatorade @ 40 minutes
1 GU @ mile 10 (63:26 into race) w/ 8 oz of Gatorade
8 oz of Gatorade @ 90 minutes
1 GU @ mile 20 (62:45 mins. later) w/8 oz of Gatorade
My questions with regards to San Francisco; am I right in suspecting that my lack of
training is to blame for my downfall in the later miles? I suspect that with increased
training I would likely be able to burn my fuel more efficiently at higher exercise
intensity, so I might make it through without hitting the wall. If I hit the wall because I
ran out of energy, why wasn’t I able to use the supplements I was taking in to prevent
this? Did I run too hard and drain an energy supply too early putting myself in too much
debt for the later miles?
Looking forward to Boston, how should I fuel versus my strategy for San Francisco?
Sincerely,
Boston Bound
Products to investigate: GU, Gatorade
Runner 4/5 (not implemented in the course, but could be used for the exam)
Dear Marathon Master,
I am running my first marathon this spring, the Madison Marathon! As the race gets
closer I can’t help but think about what I should do during the race in regards to my
nutrition. I keep seeing all of this stuff about proper fueling to avoid hitting the wall, but
Page 37
haven’t a clue about what to do. I normally have oatmeal for breakfast, so I will get up
early and do that. During the race I think the most logical thing to do will be to take in
some fluid that will replenish my energy supply. The obvious choice is an energy drink,
right? I am currently planning on taking a few sips of red bull (it will give me wings!
Right?) at miles 15, 18, and 23. I plan to take it late in the race because by then I will
have burned a lot of calories.
Sincerely,
Madison marathoner
Product to investigate: red bull
Hola Marathon Master,
I am currently training for Grandmas marathon in Duluth, MN. It will be my 3rd
marathon and I am hoping to get a personal record. Considering that I had to walk the 2nd
half of my first marathon, because of the stomach cramp I got after taking in too much
food at an aid station, I think it should be fairly easy to do if I limit my solid intake.
In my 2nd marathon I didn’t take in any solid food (just Gatorade and water), and was
doing quite well until the last 10K. Suddenly, I felt like all of my energy was gone. My
legs felt like dead weights and I didn’t know how I was going to finish. At that point I
couldn’t even remember why I signed up for it. With my limited mental capacity I
deduced that I had hit the wall. Suffice it to say, I did finish and have forgotten enough
about how that felt to sign up for Grandmas marathon.
For Grandmas, I am planning on taking water at alternating aid stations and a shot of
espresso at the 3 hr. mark. Considering the energy: volume ratio of espresso, I think this
is a brilliant plan, and will give me what I need to finish that last 10k without hitting the
wall.
Sincerely,
“Carefully Considering the Coffee” Carl
Products to investigate: espresso
Getting students started on the case:
Students were asked to examine the calorie content of the products and use “Charley’s list of
questions (pg 4) http://sciencecases.lib.buffalo.edu/cs/files/energy_drinks.pdf” to complete the
“Post Research Analysis (pg 9)” table for their runner’s supplements. All biochemical
information on the selected ingredients was provided so students didn’t have to spend a lot of
time completing the table. Students received 5 participation points for filling in their table and
for answering a list of short answer questions.
Short answer questions
New questions and previously developed questions from pg10 of
http://sciencecases.lib.buffalo.edu/cs/files/energy_drinks.pdf indicated
1. Question 1
2. Does caffeine give you energy? What is the physiological response to caffeine? (adapted
from question 3)
3. What provides more energy- sugar or fat? Which is metabolized faster?
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4. Could you simply use chocolate milk instead of one of these energy products? Why or why not?
(adapted from question 11)
5. What are the fuel requirements of your body while exercising? Where does the majority of this
energy come from?
6. Question 4 was modified to say “... marathon runner? Please discuss this in the context of
transfer of energy.”
7. Will a person running a marathon be able to metabolize/use what they are consuming during the
competition? Is the food that they are taking in being converted to usable energy during the race?
8. Compare and contrast your runner’s plan to on where the runner consumes only water during the
race. Do you think their likelihood of hitting the wall will change?
9. Aside from nutrition, what other variables might affect their potential to hit “the wall”?
Runners’ World Response (Assessment)
Individually, write a response to one of the Marathon Master readers regarding their marathon
nutrition plan. Keep your response to 1 page maximum. This should be submitted to dropbox
on Learn@UW.
Note:
 Your recommendation should be informed by your answers to the above questions.
 Your response needs to address how their current plan may impact their chance of hitting
“the wall” from a metabolic perspective.
 You must explain why you are giving your specific recommendation based on what you
know about metabolism and transfer of energy.
Additional biochemical and production information for additional
supplements
Gatorade©
Marking claims: Original Gatorade is formulated to replenish, refuel and restore the
fluids, energy and electrolytes your body needs to sustain performance levels from the
first move to the final second
Selected Ingredients: Water, Sucrose, Glucose, Fructose, Citric Acid, Sodium Chloride
http://www.foodfacts.com/NutritionFacts/Gatorade/Gatorade-Thirst-Quencher-LemonLime-32-fl-oz/47305
Nutrition: serving size: 8 fl oz, servings per container: 4; calories: 50; total fat: 0g;
sodium: 110mg, Potassium: 30mg; total carbs: 14g; Protein: 0g
References: http://www.gatorade.com/default.aspx#gseries?s=gatorade-g
PowerBar Gel©
Marking claims: PowerBar Energy Gel is the first gel to provide the carbs and
electrolytes of a high end sports drink, and contains 4 times the sodium of leading
competitors.* Sodium is the key electrolyte lost in sweat and is the only electrolyte
recommended to be replaced during endurance exercise.**
Formulated with C2 MAX, a 2:1 glucose to fructose blend found to deliver 20-50% more
energy to muscles than glucose alone and improve endurance performance by 8%***.
Contains 200 mg sodium – a key electrolyte that is associated with muscle cramping in
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some athletes. For best results, consume one PowerBar Energy Gel every 20-45 minutes
during activity, followed by a few sips of water.
*200mg sodium vs. average leading competitors' 50mg sodium.
** American College of Sports Medicine Roundtable on Hydration and Physical
Activity; Consensus Statements. Curr Sports Med Rep 2005;4:115–27.
***Currell K, Jeukendrup A. Superior Endurance Performance with Ingestion of Multiple
Transportable Carbohydrates. Med Sci Sports Exerc 2008; 40: 275–281.
Selected Ingredients: C2 MAX carbohydrate blend (glucose, fructose), water, sodium
chloride, sodium citrate, potassium chloride, caffeine
Nutrition: serving size: 1 pack, servings per container: 1, calories: 120, calories from fat:
15, fat: 1.5 g, total carbs: 28 g; sugars: 10 g; proteins: 0 g; Sodium: 200 mg; Potassium:
40 mg; Caffeine: 25 mg
References: http://www.powerbar.com/products/40/powerbar-energy-gel-chocolate.aspx
Gu (Vanilla Bean flavor) ©
Marking claims: GU provides athletes with a shot of 100 calories in the form of a
patented carbohydrate blend (70-80% maltodextrin and 30-20% fructose) to deliver highquality, easily-digested and long-lasting energy for athletes in every sport and at all
levels. GU also includes electrolytes to ensure proper hydration, an antioxidant blend to
stave off muscle tissue damage and an amino acid blend to delay muscle fatigue.
Everything inside each packet of GU is engineered to do one simple thing: provide your
body with the essential requirements it needs to keep going for miles and miles and hours
and hours. It goes down easy, and it goes to work fast so you don’t have to slow down.
Selected Ingredients: Maltodextrin, Filtered Water, Fructose, GU Amino Acid Blend
(Leucine, Valine, Isoleucine, Histidine), Potassium and Sodium Citrate, GU Antioxidant
Blend (Natural Vitamin E and Vitamin C), Citric Acid, Caffeine
Nutrition: serving size: 1 pack, calories: 100, calories from fat: 0, total fat: 0g, total
carbs: 25g, Sugars: 5g, Protein: 0g, Sodium 55mg, Potassium 45mg, 20 mg caffeine
Reference: https://guenergy.com/vanilla-bean.html
Chocolate Milk
Marking claims: Milk is an important source of many of the nutrients essential for the
proper development and maintenance of the human body.
Ingredients: Low-fat milk (8.25% "milk solids not fat" (protein, carbohydrate, watersoluble vitamins and minerals), sugar, saturated fat, calcium, cacao, starch, sodium
chloride
Nutrition: serving size 1 cup (240 mL), calories: 160, calories from fat: 25, fat: 2.5g,
total carbs: 27 g, protein: 8g, sodium: 210 mg, cholesterol: 10mg,
References: Babcock chocolate milk bottle,
http://www.havemilk.com/article.asp?id=6797,
http://dishondieting.blogspot.com/2011/04/chocolate-milk-makeovers.html
Espresso
Marking claims: none
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Ingredients: water, coffee
Nutrition: serving size: 1.5 oz., calories: 1, 96 mg of caffeine
References: http://wiki.answers.com/Q/How_many_calories_does_coffee_have,
http://www.energyfiend.com/caffeine-content/espresso
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Biochemical information provided
Taken from original case- Caffeine, Citric Acid, Glucose, Fructose, Sucrose, Water
Cacao
Chemical formula: C7H8N4O2
What it is: the dried and fully fermented fatty seed of Theobroma cacao, from which cocoa solids and
cocoa butter are extracted.
What it does: used to make chocolate
Calcium
Chemical formula: Ca2+
What it is: alkali metal
What it does: important for bone strength
Coffee (water and coffee beans)
Chemical formula: coffee beans contain seed materials, including between 1-5% caffeine
What it is: see caffeine
What it does: see caffeine
Leucine, Valine, Isoleucine, Histidine
Chemical formula: (Leu) C6H13NO2, (Val) C5H11NO2, (Ile) C6H13NO2, (His) C6H9N3O2
What they are: 4 different amino acids
What it does: They can be absorbed and used in protein synthesis
Maltodextrin
Chemical formula: (C6H12O8)n, where n varies between 3 and 17
What it is: Maltodextrin consists of D-glucose units connected in chains of variable length. Maltodextrin
is typically composed of a mixture of chains that vary from three to seventeen glucose units long.
What it does: Maltodextrin is easily digestible, being absorbed as rapidly as glucose, and might be either
moderately sweet or almost flavorless. It is commonly used for the production of sodas and candy. It can
also be found as an ingredient in a variety of other processed foods
Potassium Chloride
Chemical formula: KCl
What it is: salt
What it does: increases the ionic strength of a solution, acts as a counter ion.
Potassium Citrate
Chemical formula: C6H5K3O7
What it is: a potassium salt of citric acid.
What it does: It is a food additive used to regulate acidity.
Protein
Chemical formula: variable (it depends on which protein you are talking about)
What it is: chain of amino acids linked together. Amino acid content is protein specific
What it does: Proteins have a variety of functions. When ingested, they are broken down into individual
amino acids during digestion (by enzymes like chymotrypsin and trypsin). Individual amino acids are
used for host protein synthesis.
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Sodium Chloride
Chemical formula: NaCl
What it is: salt
What it does: increases the ionic strength of a solution, acts as a counter ion.
Saturated fat
Chemical formula: CH3(CH2)nCOOH (where n can be 3-34)
What it is: triglycerides that have only saturated fatty acids (no double bonds between individual carbon
atoms in the fatty acid chain). Each of the carbon atoms is fully “saturated” with hydrogen atoms.
What it does:
Sodium citrate
Chemical formula: Na3H2C6H5O7
What it is: an acidic salt
What it does: Sodium citrate is chiefly used as a food additive, usually for flavor or as a preservative.
Starch
Chemical formula: (C6H12O8)n, where n varies
What it is: a carbohydrate consisting of a large number of glucose units joined together by glycosidic
bonds
What it does: is broken down to individual glucose units used in glycolysis
Sugar
Chemical formula: n/a
What it is: Sugar is the generalized name for a class of sweet-flavored substances used as food. They are
carbohydrates and as this name implies, are composed of carbon, hydrogen and oxygen. There are various
types of sugar derived from different sources. Simple sugars are called monosaccharides and include
glucose, fructose and galactose. The table or granulated sugar most customarily used as food is sucrose, a
disaccharide.
What it does: Enters the primary metabolic pathway in which the chemical energy of its bonds is
converted into ATP, the primary “energy” molecule in the body.
Vitamin C
Chemical formula: C6H8O6
What it is: Vitamin C is a water-soluble vitamin that is necessary for normal growth and development.
The body is not able to make vitamin C on its own, and it does not store vitamin C. It is therefore
important to include plenty of vitamin C-containing foods in your daily diet.
What it does: Vitamin C is needed for the growth and repair of tissues in all parts of your body.
Vitamin E
Chemical formula: C29H50O2
What it is: Vitamin E is found naturally in some foods, added to others, and available as a dietary
supplement. "Vitamin E" is the collective name for a group of fat-soluble compounds with distinctive
antioxidant activities
What it does: Antioxidants protect cells from the damaging effects of free radicals, which are molecules
that contain an unshared electron. Free radicals damage cells and might contribute to the development of
cardiovascular disease and cancer. In addition to its activities as an antioxidant, vitamin E is involved in
immune function and, as shown primarily by in vitro studies of cells, cell signaling, regulation of gene
expression, and other metabolic processes.
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Website references for the product pictures:
Red bull can:
Red Bull. <http://www.le-petitdejeuner.fr/boisson-fraiche/27-red-bull.html>
Gatorade:
Bird. This is Freakin Bizarre. 5 May 2003 <http://thinklings.org/posts/what-color-is-thisliquid>
PowerBar Gel:
PowerBar Power Gel. <http://www.shopping.com/Power-Bar-PowerBar-Power-GelConcentrated-Carbohydrate-Gel-Caffeinated-Chocolate-24-1-4-oz-41-g-packages-984-g2-lb-2-oz/info>
Chocolate Milk:
Muniz, Hannah. Chocolate mile more than a simple snack. 30 January 2011.
<http://dailytrojan.com/2011/01/30/chocolate-milk-more-than-a-simple-snack/>
GU vanilla bean:
Wind in My Face. Muscle Fueling: GU Energy Gel. 23 February 2012.
<http://windinmyface.com/nutrition-onbike-GU.html>
Espresso:
Energy Fiend, The Caffeine Fix. <http://www.energyfiend.com/caffeinecontent/espresso>
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