bioenergetics_0.ppt

Scott K. Powers • Edward T. Howley
Theory and Application to Fitness and Performance
SEVENTH EDITION
Chapter
Presentation prepared by:
Brian B. Parr, Ph.D.
University of South Carolina Aiken
Copyright ©2009 The McGraw-Hill Companies, Inc. Permission required for reproduction or display outside of classroom use.
Bioenergetics

Chapter 3
Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved.
Objectives
1. Discuss the functions of the cell membrane,
nucleus, and mitochondria.
2. Define the following terms: (1) endergonic
reactions, (2) exergonic reactions, (3) coupled
reactions, and (4) bioenergetics.
3. Describe the role of enzymes as catalysts in
cellular chemical reactions.
4. List and discuss the nutrients that are used as
fuels during exercise.
5. Identify the high-energy phosphates.

Chapter 3
Objectives
6. Discuss the biochemical pathways involved in
anaerobic ATP production.
7. Discuss the aerobic production of ATP.
8. Describe the general scheme used to regulate
metabolic pathways involved in bioenergetics.
9. Discuss the interaction between aerobic and
anaerobic ATP production during exercise.
10. Identify the enzymes that are considered rate
limiting in glycolysis and the Krebs cycle.

Chapter 3
Outline
 Cell Structure
 Biological Energy
Transformation
Cellular Chemical
Reactions
Oxidation-Reduction
Reactions
Enzymes
 Fuels for Exercise
Carbohydrates
Fats
Proteins
 High-Energy
Phosphates
 Bioenergetics
Anaerobic ATP Production
Aerobic ATP production
 Aerobic ATP Tally
 Efficiency of Oxidative
Phosphorylation
 Control of
Bioenergetics
Control of ATP-PC
System
Control of Glycolysis
Control of Krebs Cycle
and Electron Transport
Chain
 Interaction Between
Aerobic/Anaerobic
ATP Production

Chapter 3
Introduction
• Metabolism
– Sum of all chemical reactions that occur in the body
– Anabolic reactions
 Synthesis of molecules
– Catabolic reactions
 Breakdown of molecules
• Bioenergetics
– Converting foodstuffs (fats, proteins, carbohydrates)
into energy

Chapter 3
Cell Structure
Cell Structure
• Cell membrane
– Semipermeable membrane that separates the cell
from the extracellular environment
• Nucleus
– Contains genes that regulate protein synthesis
 Molecular biology
• Cytoplasm
– Fluid portion of cell
– Contains organelles
 Mitochondria

Chapter 3
Cell Structure
A Typical Cell and Its Major Organelles
Figure 3.1

Chapter 3
In Summary
 Metabolism is defined as the total of all cellular reactions
that occur in the body; this includes both the synthesis of
molecules and the breakdown of molecules.
 Cell structure includes the following three major parts:
(1) cell membrane, (2) nucleus, and (3) cytoplasm
(called sarcoplasm in muscle).
 The cell membrane provides a protective barrier
between the interior of the cell and the extracellular fluid.
 Genes (located within the nucleus) regulate protein
synthesis within the cell.
 The cytoplasm is the fluid portion of the cell and contains
numerous organelles
Cell Structure

Chapter 3
A Closer Look 3.1
Molecular Biology and Exercise Science
• Study of molecular structures and events
underlying biological processes
– Relationship between genes and cellular
characteristics they control
• Genes code for specific cellular proteins
– Process of protein synthesis
• Exercise training results in modifications in protein
synthesis
– Strength training results in increased synthesis of
muscle contractile protein
• Molecular biology provides “tools” for
understanding the cellular response to exercise
Cell Structure

Chapter 3
Steps Leading to Protein Synthesis
Figure 3.2
1. DNA contains
information to
produce proteins.
2. Transcription
produces mRNA.
3. mRNA leaves
nucleus and binds to
ribosome.
4. Amino acids are
carried to the
ribosome by tRNA.
5. In translation, mRNA
is used to determine
the arrangement of
amino acids in the
polypeptide chain.
Biological Energy Transformation

Chapter 3
Cellular Chemical Reactions
• Endergonic reactions
– Require energy to be added
– Endothermic
• Exergonic reactions
– Release energy
– Exothermic
• Coupled reactions
– Liberation of energy in an exergonic reaction drives
an endergonic reaction

Chapter 3
The Breakdown of Glucose:
An Exergonic Reaction
Figure 3.3

Chapter 3
Figure 3.4
The energy given off by the exergonic reaction
powers the endergonic reaction
Coupled Reactions

Chapter 3
Oxidation-Reduction Reactions
• Oxidation
– Removing an electron
• Reduction
– Addition of an electron
• Oxidation and reduction are always coupled
reactions
• Often involves the transfer of hydrogen atoms
rather than free electrons
– Hydrogen atom contains one electron
– A molecule that loses a hydrogen also loses an
electron and therefore is oxidized
• Importance of NAD and FAD

Chapter 3
Oxidation-Reduction Reaction Involving
NAD and NADH
Figure 3.5

Chapter 3
Enzymes
• Catalysts that regulate the speed of reactions
– Lower the energy of activation
• Factors that regulate enzyme activity
– Temperature
– pH
• Interact with specific substrates
– Lock and key model

Chapter 3
Enzymes Catalyze Reactions
Figure 3.6
Enzymes lower the energy of activation

Chapter 3
The Lock-and-Key Model of Enzyme
Action
Figure 3.7
a) Substrate (sucrose)
approaches the
active site on the
enzyme.
b) Substrate fits into
the active site,
forming enzyme-
substrate complex.
c) The enzyme
releases the
products (glucose
and fructose).

Chapter 3
Clinical Applications 3.1
Diagnostic Value of Measuring Enzyme
Activity in the Blood
• Damaged cells release enzymes into the blood
– Enzyme levels in blood indicate disease or tissue
damage
• Diagnostic application
– Elevated lactate dehydogenase or creatine kinase in
the blood may indicate a myocardial infarction

Chapter 3
Examples of the Diagnostic Value of
Enzymes in Blood

Chapter 3
Classification of Enzymes
• Oxidoreductases
– Catalyze oxidation-reduction reactions
• Transferases
– Transfer elements of one molecule to another
• Hydrolases
– Cleave bonds by adding water
• Lyases
– Groups of elements are removed to form a double bond or
added to a double bond
• Isomerases
– Rearrangement of the structure of molecules
• Ligases
– Catalyze bond formation between substrate molecules

Chapter 3
Example of the Major Classes of
Enzymes

Chapter 3
Factors That Alter Enzyme Activity
• Temperature
– Small rise in body temperature increases enzyme
activity
– Exercise results in increased body temperature
• pH
– Changes in pH reduces enzyme activity
– Lactic acid produced during exercise

Chapter 3
The Effect of Body Temperature on
Enzyme Activity
Figure 3.8

Chapter 3
The Effect of pH on Enzyme Activity
Figure 3.9

Chapter 3
Carbohydrates
• Glucose
– Blood sugar
• Glycogen
– Storage form of glucose in liver and muscle
 Synthesized by enzyme glycogen synthase
– Glycogenolysis
 Breakdown of glycogen to glucose
Fuels for Exercise

Chapter 3
Fats
• Fatty acids
– Primary type of fat used by the muscle
– Triglycerides
 Storage form of fat in muscle and adipose tissue
 Breaks down into glycerol and fatty acids
• Phospholipids
– Not used as an energy source
• Steroids
– Derived from cholesterol
– Needed to synthesize sex hormones
Fuels for Exercise

Chapter 3
Fuels for Exercise
Protein
• Composed of amino acids
• Some can be converted to glucose in the liver
– Gluconeogenesis
• Others can be converted to metabolic intermediates
– Contribute as a fuel in muscle
• Overall, protein is not a primary energy source
during exercise

Chapter 3
In Summary
 The body uses carbohydrate, fat, and protein nutrients
consumed daily to provide the necessary energy to
maintain cellular activities both at rest and during
exercise. During exercise, the primary nutrients used for
energy are fats and carbohydrates, with protein
contributing a relatively small amount of the total energy
used.
 Glucose is stored in animal cells as a polysaccharide
called glycogen.
 Fatty acids are the primary form of fat used as an energy
source in cells. Fatty acids are stored as triglycerides in
muscle and fat cells.
Fuels for Exercise

Chapter 3
• Adenosine triphosphate (ATP)
– Consists of adenine, ribose, and three linked
phosphates
• Synthesis
• Breakdown
ADP + Pi  ATP
ADP + Pi + Energy
ATP ATPase
High-Energy Phosphates

Chapter 3
Structure of ATP
Figure 3.10

Chapter 3
Model of ATP as the Universal Energy
Donor
Figure 3.11

Chapter 3
Bioenergetics
• Formation of ATP
– Phosphocreatine (PC) breakdown
– Degradation of glucose and glycogen
 Glycolysis
– Oxidative formation of ATP
• Anaerobic pathways
– Do not involve O2
– PC breakdown and glycolysis
• Aerobic pathways
– Require O2
– Oxidative phosphorylation
Bioenergetics

Chapter 3
ATP + C
PC + ADP Creatine kinase
Anaerobic ATP Production
• ATP-PC system
– Immediate source of ATP
• Glycolysis
– Glucose  2 pyruvic acid or 2 lactic acid
– Energy investment phase
 Requires 2 ATP
– Energy generation phase
 Produces 4 ATP, 2 NADH, and 2 pyruvate or 2 lactate
Bioenergetics

Chapter 3
The Winning Edge 3.1
Does Creatine Supplementation
Improve Exercise Performance?
• Depletion of PC may limit short-term, high-intensity
exercise
• Creatine monohydrate supplementation
– Increased muscle PC stores
– Some studies show improved performance in short-
term, high-intensity exercise
 Inconsistent results may be due to water retention and
weight gain
– Increased strength and fat-free mass with resistance
training
• Creatine supplementation does not appear to pose
health risks
Bioenergetics

Chapter 3
A Closer Look 3.2
Lactic Acid or Lactate?
• Terms lactic acid and lactate used interchangeably
– Lactate is the conjugate base of lactic acid
• Lactic acid is produced in glycolysis
– Rapidly disassociates to lactate and H+
Figure 3.12
The ionization of lactic acid forms the
conjugate base called lactate
Bioenergetics

Chapter 3
The Two Phases of Glycolysis
Figure 3.13
Bioenergetics

Chapter 3
Interaction Between Blood Glucose and
Muscle Glycogen in Glycolysis
Figure 3.14
Bioenergetics

Chapter 3
Bioenergetics
Figure 3.15
Glycolysis: Energy Investment Phase

Chapter 3
Glycolysis: Energy Generation Phase
Bioenergetics
Figure 3.15

Chapter 3
• Transport hydrogens and associated electrons
– To mitochondria for ATP generation (aerobic)
– To convert pyruvic acid to lactic acid (anaerobic)
• Nicotinamide adenine dinucleotide (NAD)
• Flavin adenine dinucleotide (FAD)
NAD + 2H+  NADH + H+
FAD + 2H+  FADH2
Hydrogen and Electron Carrier
Molecules
Bioenergetics

Chapter 3
A Closer Look 3.3
NADH is “Shuttled” into Mitochondria
• NADH produced in glycolysis must be converted
back to NAD
– By converting pyruvic acid to lactic acid
– By “shuttling” H+ into the mitochondria
• A specific transport system shuttles H+ across the
mitochondrial membrane
– Located in the mitochondrial membrane
Bioenergetics

Chapter 3
Conversion of Pyruvic Acid to Lactic Acid
Figure 3.16
The addition of two H+ to pyruvic acid forms NAD and lactic acid
Bioenergetics

Chapter 3
 The immediate source of energy for muscular contraction
is the high-energy phosphate ATP. ATP is degraded via
the enzyme ATPase as follows:
 Formation of ATP without the use of O2 is termed
anaerobic metabolism. In contrast, the production of ATP
using O2 as the final electron acceptor is referred to as
aerobic metabolism.
In Summary
ADP + Pi + Energy
ATP ATPase
Bioenergetics

Chapter 3
 Exercising skeletal muscles produce lactic acid.
However, once produced in the body, lactic acid is
rapidly converted to its conjugate base, lactate.
 Muscle cells can produce ATP by any one or a
combination of three metabolic pathways: (1) ATP-PC
system, (2) glycolysis, (3) oxidative ATP production.
 The ATP-PC system and glycolysis are two anaerobic
metabolic pathways that are capable of producing ATP
without O2.
In Summary
Bioenergetics

Chapter 3
Bioenergetics
Aerobic ATP Production
• Krebs cycle (citric acid cycle)
– Pyruvic acid (3 C) is converted to acetyl-CoA (2 C)
 CO2 is given off
– Acetyl-CoA combines with oxaloacetate (4 C) to
form citrate (6 C)
– Citrate is metabolized to oxaloacetate
 Two CO2 molecules given off
– Produces three molecules of NADH and one FADH
– Also forms one molecule of GTP
 Produces one ATP

Chapter 3
The Three
Stages
of Oxidative
Phosphorylation
Figure 3.17
Bioenergetics

Chapter 3
The Krebs Cycle
Figure 3.18
Bioenergetics

Chapter 3
Bioenergetics
Fats and Proteins in Aerobic Metabolism
• Fats
– Triglycerides  glycerol and fatty acids
– Fatty acids  acetyl-CoA
 Beta-oxidation
– Glycerol is not an important muscle fuel during
exercise
• Protein
– Broken down into amino acids
– Converted to glucose, pyruvic acid, acetyl-CoA, and
Krebs cycle intermediates

Chapter 3
Bioenergetics
Figure 3.19
Relationship Between the Metabolism of
Proteins, Carbohydrates, and Fats

Chapter 3
Aerobic ATP Production
• Electron transport chain
– Oxidative phosphorylation occurs in the
mitochondria
– Electrons removed from NADH and FADH are
passed along a series of carriers (cytochromes) to
produce ATP
 Each NADH produces 2.5 ATP
 Each FADH produces 1.5 ATP
– Called the chemiosmotic hypothesis
– H+ from NADH and FADH are accepted by O2 to
form water
Bioenergetics

Chapter 3
Bioenergetics
The Chemiosmotic Hypothesis of ATP
Formation
• Electron transport chain results in pumping of H+
ions across inner mitochondrial membrane
– Results in H+ gradient across membrane
• Energy released to form ATP as H+ ions diffuse
back across the membrane

Chapter 3
Figure 3.20
The Electron Transport Chain
Bioenergetics

Chapter 3
A Closer Look 3.4
Beta Oxidation is the Process of
Converting Fatty Acids to Acetyl-CoA
• Breakdown of triglycerides releases fatty acids
• Fatty acids must be converted to acetyl-CoA to be
used as a fuel
– Activated fatty acid (fatty acyl-CoA) into
mitochondrion
– Fatty acid “chopped” into 2 carbon fragments
forming acetyl-CoA
• Acetyl-CoA enters Krebs cycle and is used for
energy
Bioenergetics

Chapter 3
Beta Oxidation
Figure 3.21
Bioenergetics

Chapter 3
 Oxidative phosphorylation or aerobic ATP production
occurs in the mitochondria as a result of a complex
interaction between the Krebs cycle and the electron
transport chain. The primary role of the Krebs cycle is to
complete the oxidation of substrates and form NADH and
FADH to enter the electron transport chain. The end
result of the electron transport chain is the formation of
ATP and water. Water is formed by oxygen-accepting
electrons; hence, the reason we breathe oxygen is to
use it as the final acceptor of electrons in aerobic
metabolism.
In Summary
Bioenergetics

Chapter 3
A Closer Look 3.5
A New Look at the ATP Balance Sheet
• Historically, 1 glucose produced 38 ATP
• Recent research indicates that 1 glucose produces
32 ATP
– Energy provided by NADH and FADH also used to
transport ATP out of mitochondria.
– 3 H+ must pass through H+ channels to produce 1
ATP
– Another H+ needed to move the ATP across the
mitochondrial membrane
Aerobic ATP Tally

Chapter 3
Metabolic Process High-Energy
Products
ATP from Oxidative
Phosphorylation
ATP Subtotal
Glycolysis 2 ATP
2 NADH
—
5
2 (if anaerobic)
7 (if aerobic)
Pyruvic acid to acetyl-CoA 2 NADH 5 12
Krebs cycle 2 GTP
6 NADH
2 FADH
—
15
3
14
29
32
Grand Total 32
Aerobic ATP Tally Per Glucose Molecule
Aerobic ATP Tally

Chapter 3
32 moles ATP/mole glucose x 7.3 kcal/mole ATP
686 kcal/mole glucose
x 100 = 34%
Efficiency of Oxidative Phosphorylation
• One mole of ATP has energy yield of 7.3 kcal
• 32 moles of ATP are formed from one mole of
glucose
• Potential energy released from one mole of glucose
is 686 kcal/mole
• Overall efficiency of aerobic respiration is 34%
– 66% of energy released as heat

Chapter 3
 The aerobic metabolism of one molecule of glucose
results in the production of 32 ATP molecules, whereas
the aerobic yield for glycogen breakdown is 33 ATP.
 The overall efficiency of aerobic of aerobic respiration is
approximately 34%, with the remaining 66% of energy
being released as heat.
In Summary

Chapter 3
Control of Bioenergetics
• Rate-limiting enzymes
– An enzyme that regulates the rate of a metabolic
pathway
• Modulators of rate-limiting enzymes
– Levels of ATP and ADP+Pi
 High levels of ATP inhibit ATP production
 Low levels of ATP and high levels of ADP+Pi stimulate ATP
production
– Calcium may stimulate aerobic ATP production

Chapter 3
Figure 3.22
Example of a Rate-Limiting Enzyme

Chapter 3
Factors Known to Affect Rate-Limiting
Enzymes
Pathway Rate-Limiting
Enzyme
Stimulators Inhibitors
ATP-PC system Creatine kinase ADP ATP
Glycolysis Phosphofructokinase AMP, ADP, Pi, pH ATP, CP, citrate, pH
Krebs cycle Isocitrate
dehydrogenase
ADP, Ca
++
, NAD ATP, NADH
Electron transport
chain
Cytochrome Oxidase ADP, Pi ATP

Chapter 3
 Metabolism is regulated by enzymatic activity. An
enzyme that regulates a metabolic pathway is termed a
“rate-limiting” enzyme.
 The rate-limiting enzyme for glycolysis is
phosphofructokinase, while the rate-limiting enzymes for
the Krebs cycle and electron transport chain are
isocitrate dehydrogenase and cytochrome oxidase,
respectively.
 In general, cellular levels of ATP and ADP+Pi regulate
the rate of metabolic pathways involved in the production
of ATP. High levels of ATP inhibit further ATP
production, while low levels of ATP and high levels of
ADP+Pi stimulate ATP production. Evidence also exists
that calcium may stimulate aerobic energy metabolism.
In Summary

Chapter 3
Interaction Between Aerobic/Anaerobic
ATP Production
• Energy to perform exercise comes from an
interaction between aerobic and anaerobic
pathways
• Effect of duration and intensity
– Short-term, high-intensity activities
 Greater contribution of anaerobic energy systems
– Long-term, low to moderate-intensity exercise
 Majority of ATP produced from aerobic sources
Interaction Between Aerobic/Anaerobic ATP Production

Chapter 3
Figure 3.23
The Winning Edge 3.2
Contribution of Aerobic/Anaerobic ATP
Production During Sporting Events

Chapter 3
 Energy to perform exercise comes from an interaction of
anaerobic and aerobic pathways.
 In general, the shorter the activity (high intensity), the
greater the contribution of anaerobic energy production.
In contrast, long-term activities (low to moderate
intensity) utilize ATP produced from aerobic sources.
In Summary

Chapter 3
Study Questions
1. List and briefly discuss the functions of the three
major components of cell structure.
2. Briefly explain the concept of coupled reactions.
3. Define the following terms: (1) bioenergetics, (2)
endergonic reactions, and (3) exergonic reactions.
4. Discuss the role of enzymes as catalysts. What is
meant by the expression “energy of activation”?
5. Where do glycolysis, the Krebs cycle, and
oxidative phosphorylation take place in the cell?
6. Define the terms glycogen, glycogenolysis, and
glycolysis.

Chapter 3
Study Questions
7. What are the high-energy phosphates? Explain
the statement that “ATP is the universal energy
donor.”
8. Define the terms aerobic and anaerobic.
9. Briefly discuss the function of glycolysis in
bioenergetics. What role does NAD play in
glycolysis?
10. Discuss the operation of the Krebs cycle and the
electron transport chain in the aerobic production
of ATP. What is the function of NAD and FAD in
these pathways?

Chapter 3
Study Questions
11. What is the efficiency of the aerobic degradation
of glucose?
12. What is the role of oxygen in aerobic metabolism?
13. What are the rate-limiting enzymes for the
following metabolic pathways: ATP-PC system,
glycolysis, Krebs cycle, and electron transport
chain?
14. Briefly discuss the interaction of anaerobic versus
aerobic ATP production during exercise.
15. Discuss the chemiosmotic theory of ATP
production.

Chapter 3
Study Questions
16. List and define the six classes of enzymes
identified by the International Union of
Biochemistry.
17. Briefly discuss the impact of changes in both
temperature and pH on enzyme function.
18. Discuss the relationship between lactic acid and
lactate.

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