Download Chemistry and the Gym

Chemistry
and the Gym
Learning Objectives
a. Exercise can be aerobic (sustained physical
activity with O2) or anaerobic (bursts of effort
that do not have sufficient O2 to metabolize
fuels).
b. The aerobic pathway is much more efficient than
the anaerobic pathway at producing ATP to
power muscle movement.
c. The rate at which oxygen is delivered to the
muscles (VO2 max) is one of the limits to the
level of aerobic activity.
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Learning Objectives (cont)
d. Athletic training results in a number of
adaptations that increase muscle efficiency and
delivery of fuel and oxygen to the tissues.
e. Some individuals may have “thrifty genes” that
result in decreased energy expenditure for basic
life functions. Exercise can help increase energy
output, even in the resting state.
f. Exercise lowers the risk of some chronic
diseases.
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Learning Objectives (cont)
g. Strategies to improve athletic performance
include increasing delivery of fuel and/or oxygen
to the muscles.
h. Illegitimate performance enhancers include
anabolic steroids and human growth hormone to
build muscle mass and erythropoietin and blood
doping to improve oxygen delivery.
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Outline
•
The Molecular Basis of Exercise
a. Aerobic vs. Anaerobic Activity
b. ATP, the Cell’s Energy Currency, is called
adenosine triphosphate
c. Fuels that Power Exercise
1. Primarily fats and carbohydrates (glucose or
glycogen).
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Energy
Requirements Vary with Activity
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Fuel
Reserves for a Typical 70-kg Male
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Many of the carbon
atoms in glucose have ―OH substituents
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Glycolysis
1st stage in the breakdown of glucose to produce ATP is glycolysis (greek
words means sweet and splitting)
Adenosine diphosphate
ADP
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Outline
•
The Molecular Basis of Exercise (cont)
d. Mobilization of Fuels
1. During glycolysis, glucose is oxidized to pyruvate
and ATP is produced.
2. Pyruvate can be oxidized in the efficient aerobic
pathway (cellular respiration) or converted to lactic
acid in the anaerobic pathway (fermentation).
3. The rate at which oxygen is delivered to the
muscles (VO2 max) dictates the level of activity
that can be sustained under aerobic conditions.
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Alternate Fates of Pyruvate
Cellular respiration occurs in the mitochondria, the cell’s “powerhouse”. It
traps the maximum amount of chemical energy stored within a molecule of
glucose, generating an additional 30 molecules of ATP per pair of pyruvate
molecules.
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Gerty and
Carl Cori, 1947 Nobel Prize winners
In 1947, they shared the Nobel prize in
Physiology or Medicine for their work
on glucose metabolism, including
characterizing the relationship between
liver and muscle glycogen stores.
Credit: Corbis
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Path of glucose metabolism
During anaerobic metabolism,
muscle glycogen is converted to
glucose and then to lactic acid,
which circulates to the liver,
where it is converted back to
glycogen. When needed, the
liver replenishes blood glucose,
which is taken up by the
muscles to form glycogen,
completing the cycle.
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Energy Sources for
Powering Muscles During Exercise
Credit: P. L. Greenhaff, E. Hultman, and R. C. Harris. In J. R. Poortmans (ed.),
Principles of Exercise Biochemistry, 3rd. rev. ed. Basel: Karger, 2004, pp. 108–151.
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VO2 max is
determined by measuring oxygen exhaled
VO2 max is determined in the
laboratory by measuring the amount
of oxygen exhaled, allowing the
calculation of how much is
consumed. Therefore determinants
of VO2 max include the hematocrit
(the percentage of red cells in a
volume of blood)
Credit: Photo Researchers, Inc.
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Outline
•
The Chemistry of Muscles
a. Muscle Contraction
1. ATP powers muscle contraction, in which the thick
filaments (made of the protein myosin) slide past the
thin filaments (made of the protein actin).
b. Types of Muscle Fibers
1. Slow-twitch muscle fibers, which are enriched in
myoglobin, are designed for aerobic activity.
2. Fast-twitch muscle fibers, which lack myoglobin, are
designed for anaerobic activity.
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Muscle Contraction
Muscles are made up of the
proteins myosin and actin.
The muscle protein
myoglobin picks up oxygen
from hemoglobin and
delivers it to the
mitochondria for use in
cellular respiration.
2 types of muscle fibers:
Type I or slow-twitch muscle
fibers are designed for aerobic
activity because they contract
slowly and steadily.
Type II or fast-twitch muscle
fibers are designed for anaerobic
activity. They are stronger and
larger than Type I
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Outline
•
Physiological Aspects of Exercise
a. Endurance (Aerobic) Training
1. Slow-twitch muscles become larger.
2. Amounts of myoglobin and mitochondria in the
muscles increase.
3. VO2 max increases.
4. Levels of key enzymes for fat metabolism
increase.
5. Glycogen stores increase.
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Outline
•
Physiological Aspects of Exercise (cont)
b. Anaerobic Training
1. Fast-twitch muscles become larger.
2. Stores of ATP, phosphocreatine, and glycogen
increase.
3. Capacity for lactic acid increases.
4. Levels of key enzymes for glycolysis increase.
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Outline
•
Physiological Aspects of Exercise (cont)
c. Depletion of Energy Reserves
1. When carbohydrate stores are exhausted,
hypoglycemia (low blood sugar levels) set in.
d. Hormones
1. Chemical signals that mediate metabolic changes that
occur during exercise; e.g., adrenaline prepares for
“fight or flight”
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Examples of
Hormones Involved in Exercise
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Outline
•
Physiological Aspects of Exercise (cont)
e. Runner’s High
1. Endorphins are natural painkillers (made by the
body) produced during times of physical stress.
f. Sex Differences
1. Women generally have greater fat stores than men,
making them well suited for aerobic endurance
events.
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Outline
•
Exercise and Weight Control
a. Energy Balance
1. Energy In = Food Consumed
2. Energy Out = Exercise, Basal Metabolism,
Thermogenesis
b. The Thrifty Gene Hypothesis
1. “Thrifty genes” may allow some individuals to
maintain life processes with very little food intake.
2. Thrifty gene effects may be related to the hormone
leptin.
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Effect of Leptin on Body Mass
Leptin is a peptide
hormone that
mediates body
weight, metabolism,
and reproduction.
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Outline
•
Exercise and Chronic Disease
a. The risk factors for many chronic diseases,
including heart disease and diabetes are
decreased by exercise.
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Outline
•
Legal Performance Enhancers
a. Carbo-Loading
1. Increases glycogen stores, delaying the onset of
hypoglycemia
b. Carnitine
1. Escorts fatty acids into the mitochondria for
oxidation, maximizing fat burning and conserving
glycogen.
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Carnitine
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Outline
•
Legal Performance Enhancers (cont)
c. Creatine
1. Increases stores of phosphocreatine, the muscle’s
quickest energy source
d. Electrolyte-Replacement (Gatorade)
1. Provides water, essential electrolytes, and
carbohydrates
e. Altitude Training
1. Increases the number of red blood cells (the
hematocrit) and the amount of hemoglobin
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Composition
of Various ERG Beverages
Electrolyte replacement glucose (ERG) is a beverage that
supplies water, electrolytes, and carbohydrates.
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Outline
•
Illegal Performance Enhancers
a. Improving Oxygen Delivery
1. Blood Doping: red blood cells are removed several
weeks prior to competition; body responds by
making more red blood cells; right before
competition, athlete receives a blood transfusion.
2. Erythropoietin (EPO): hormone that promotes the
production of red blood cells
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Effect of EPO (Erythropoietin) on
Hematocrit
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Outline
•
Illegal Performance Enhancers (cont)
b. Building Muscle Mass
1. Anabolic steroids (means building up):
structurally similar to the male sex hormone
testosterone
2. Human growth hormone (hGH) to achieve
the same effects but without using Anabolic
steroids.
Side effects of hGH include enlargement of the extremities,
such as hands and feet, diabetes, enlarged internal organs,
and increased risk of cardiovascular disease, all of which may
result in premature death.
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Mark McGwire legally
used anabolic steroids in his record-setting 1998
season
Credit: Getty Images
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Anabolic Steroids
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Key Words
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•
•
•
•
•
•
•
•
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Aerobic
Anaerobic
ATP (adenosine
triphosphate)
Adipose tissue
Glycolysis
Cellular respiration
Fermentation
VO2 max
Hematocrit
Slow-twitch muscle fibers
(Type I)
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•
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•
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•
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Fast-twitch muscle
fibers (Type II)
Hypoglycemia
Hormones
Endorphins
Leptin
Hyperthermia
Erythropoietin
(EPO)
Anabolic steroids
Testosterone
Human growth
hormone (hGH)
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