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

2. Introduction Metabolism Bioenergetics
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 Nucleus Cytoplasm
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
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, Paget’s 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 <-->Pyruvate + 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 Fats Proteins 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
ADP + Pi + Energy
ATP
ATPase

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
ATP + C
PC + ADP
Creatine kinase

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
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
32 moles ATP/mole glucose x 7.3 kcal/mole ATP
686 kcal/mole glucose
x 100 = 34%

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 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

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