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Chapter 3 Bioenergetics

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Title: Chapter 3 Bioenergetics


1
Chapter 3 Bioenergetics
  • EXERCISE PHYSIOLOGY
  • Theory and Application to Fitness and
    Performance, 6th edition
  • Scott K. Powers Edward T. Howley

2
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

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

4
A Typical Cell and Its Major Organelles
Figure 3.1
5
Steps Leading to Protein Synthesis
Figure 3.2
6
Cellular Chemical Reactions
  • Endergonic reactions
  • Require energy to be added
  • Exergonic reactions
  • Release energy
  • Coupled reactions
  • Liberation of energy in an exergonic reaction
    drives an endergonic reaction

7
The Breakdown of Glucose An Exergonic Reaction
Figure 3.3
8
Coupled Reactions
Figure 3.4
9
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

10
Oxidation-Reduction Reaction involving NAD and
NADH
Figure 3.5
11
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

12
Enzymes Catalyze Reactions
Figure 3.6
13
The Lock-and-Key Model of Enzyme Action
Figure 3.7
14
Diagnostic Value of Measuring Enzyme Activity in
the Blood
  • Enzyme Diseases Associated w/ High Blood
    Levels of Enzyme
  • Lactate dehydrogenase (Cardiac-specific
    isoform) Myocardial infarction
  • Creatin kinase Myocardial infarction, muscular
    dystrophy
  • Alkaline phosphatase Carcinoma of bone, Pagets
    disease, obstructive jaundice
  • Amylase Pancreatitis, perforated peptic ulcer
  • Aldolase Muscular dystrophy

Table 3.1
15
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

16
Example of the Major Classes of Enzymes
  • Example of Enzyme
  • Enzyme Class within this Class Reaction Catalyzed
  • Oxidoreducatases Lactate dehydrogenase
    Lactate NAD lt--gtPyruvate NADH H
  • Transferases Hexokinase Glucose ATP ?
    Glucose 6-phosphate ADP
  • Hydrolases Lipase Triglyceride 3 H20 ?
    Glycerol 3 Fatty acids
  • Lyases Carbonic anhydrase Carbon dioxide
    H20 ? Carbonic acid
  • Isomerases Phosphoglycerate
    mutase 3-Phosphoglycerate ? 2-Phosphoglycerate
  • Ligases Pyruvate carboxylase Pyruvate HC03
    ATP ? Oxaloacetate ADP

Table 3.2
17
Factors That Alter Enzyme Activity
  • Temperature
  • Small rise in body temperature increases enzyme
    activity
  • pH
  • Changes in pH reduces enzyme activity

18
The Effect of Body Temperature on Enzyme Activity
Figure 3.8
The Effect of pH on Enzyme Activity
Figure 3.9
19
Fuels for Exercise
  • Carbohydrates
  • Glucose
  • Glycogen
  • Storage form of glucose in liver and muscle
  • Fats
  • Fatty acids
  • Triglycerides
  • Storage form of fat in muscle and adipose tissue
  • Proteins
  • Not a primary energy source during exercise

20
High-Energy Phosphates
  • Adenosine triphosphate (ATP)
  • Consists of adenine, ribose, and three linked
    phosphates
  • Synthesis
  • Breakdown

ADP Pi ? ATP
21
Structure of ATP
Figure 3.10
22
Model of ATP as the Universal Energy Donor
Figure 3.11
23
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

24
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

25
The Two Phases of Glycolysis
Figure 3.12
26
Interaction Between Blood Glucose and Muscle
Glycogen in Glycolysis
Figure 3.14
27
Glycolysis Energy Investment Phase
Figure 3.15
28
Glycolysis Energy Generation Phase
Figure 3.15
29
Hydrogen and Electron Carrier Molecules
  • 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
30
Conversion of Pyruvic Acid to Lactic Acid
Figure 3.16
31
Aerobic ATP Production
  • Krebs cycle (citric acid cycle)
  • Completes the oxidation of substrates
  • Produces NADH and FADH to enter the electron
    transport chain
  • Electron transport chain
  • Oxidative phosphorylation
  • Electrons removed from NADH and FADH are passed
    along a series of carriers to produce ATP
  • H from NADH and FADH are accepted by O2 to form
    water

32
The Three Stages of Oxidative Phosphorylation
Figure 3.17
33
The Krebs Cycle
Figure 3.18
34
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

35
Relationship Between the Metabolism of Proteins,
Carbohydrates, and Fats
Figure 3.19
36
Beta-oxidation
Figure 3.21
37
The Electron Transport Chain
Figure 3.20
38
Aerobic ATP Tally Per Glucose Molecule
Table 3.3
39
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

40
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 ADPPi
  • High levels of ATP inhibit ATP production
  • Low levels of ATP and high levels of ADPPi
    stimulate ATP production
  • Calcium may stimulate aerobic ATP production

41
Action of Rate-Limiting Enzymes
Figure 3.24
42
Interaction Between Aerobic and 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

43
Effect of Event Duration on the Contribution of
Aerobic/Anaerobic ATP Production
Figure 3.24
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