1. Review of Bioenergetics
SP5005 Physiology
Alex Nowicky
power point slides: Powers and Howley- Exercise Physiology Ch 3 and 4

2. What is bioenergetics? Study of energy in living systems what it is?
Where does it come from?
How is it measured?
How is it produced and used by human body at rest and during exercise?
Part of science of biochemistry -studies conversion of matter into energy by living systems

3. For your own study use any ex physiology text and cover the following:
Energy sources
recovery from exercise
measurement of energy, work and power
This lecture is an overview of these!

4. Aim: review energy metabolism
Learning outcomes
ATP is central to all energy transactions
Oxidation (O2) (in mitochondria) central
define aerobic and anaerobic pathways - systems of enzymes and their regulation
fate of fuels - CHO, fats and proteins- relative yields of useful energy (ATP)

5. Learning outcomes (con’t)
role of glycogenolysyis, -oxidation, gluconeogenesis
indirect calorimetry for monitoring energy expenditure- oxygen consumption- (RER)
contribution of fuel supply during exercise (short vs. long duration)
role aerobic and anaerobic systems during exercise and recovery

6. Metabolism Total of all chemical reactions that occur in the body
Anabolic reactions
Synthesis of molecules
Catabolic reactions
Breakdown of molecules
Bioenergetics- oxidation (O2)
Converting foodstuffs (fats, proteins, carbohydrates) into energy

7. 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

8. The Breakdown of Glucose: An Exergonic Reaction

9. Coupled Reactions

10. Enzymes Catalysts that regulate the speed of reactions
Lower the energy of activation
Factors that regulate enzyme activity
Temperature (what happens with changes in T?)
pH ( what happens with changes in pH?)
Interact with specific substrates
Lock and key model

11. Fuels for Exercise Carbohydrates Fats Proteins Glucose
Stored as glycogen in liver and muscle
Fats
Primarily fatty acids
Stored as triglycerides- adipose tissue and muscles
Proteins
Not a primary energy source during exercise

12. High-Energy Phosphates
Adenosine triphosphate (ATP)
Consists of adenine, ribose, and three linked phosphates
Formation
Breakdown
ADP + Pi  ATP
ADP + Pi + Energy
ATP
ATPase

13. Model of ATP as the Universal Energy Donor

14. Carbohydrate
w Readily available (if included in diet) and easily metabolized by muscles
w Ingested, then taken up by muscles and liver and converted to glycogen
w Glycogen stored in the liver is converted back to glucose as needed and transported by the blood to the muscles to form ATP

15. Fat (triglycerides)
w Provides substantial energy during prolonged, low-intensity activity- light weight (little water in storage)
w Body stores of fat are larger than carbohydrate reserves
w Less accessible for metabolism because it must be reduced to glycerol and free fatty acids (FFA)
w Only FFAs are used to form ATP- triglycerides- must be broken down by process of lipolysis

16. Protein - Body uses little protein during rest and exercise (less than 5% to 10%).
w Can be used as energy source if converted to glucose via glucogenesis (or gluconeogenesis)
w Can generate FFAs in times of starvation through lipogenesis
w Only basic units of protein—amino acids—can be used for energy- via transamination feed into Kreb’s cycle
waste produce is ammonia - must be excreted (as urea)

17. Oxidation of Fat- FFA via - oxidation
w Lypolysis—breakdown of triglycerides into glycerol and free fatty acids (FFAs).
w FFAs travel via blood to muscle fibers and are broken down by enzymes in the mitochondria into acetyl CoA.
w Acetyl CoA enters the Krebs cycle and the electron transport chain.
w Fat oxidation requires more oxygen and generates more energy than carbohydrate oxidation.

18. What Determines Oxidative Capacity?
w Oxidative enzyme activity within the muscle
w Fiber-type composition and number of mitochondria
w Endurance training
w Oxygen availability and uptake in the lungs

19. Bioenergetics Formation of ATP Anaerobic pathways
Phosphocreatine (PC) breakdown
Degradation of glucose and glycogen (glycolysis)
Oxidative formation of ATP
Anaerobic pathways
Do not involve O2
PC breakdown and glycolysis (lactate)
Aerobic pathways- only occur in mitochondria
Electron transport system (ETS) -Requires O2
Oxidative phosphorylation

20. Anaerobic ATP Production
ATP-PC system
Immediate source of ATP
Glycolysis
Energy investment phase
Requires 2 ATP
Energy generation phase
Produces ATP, NADH (carrier molecule), and pyruvate or lactate
PC + ADP
ATP + C
Creatine kinase

21. RECREATING ATP WITH PCr

22. ATP AND PCr DURING SPRINTING
What does this show?

23. The Two Phases of Glycolysis

24. Glycolysis: Energy Investment Phase

25. Glycolysis: Energy Generation Phase

26. Oxidation-Reduction Reactions
Molecule accepts electrons (along with H+)
Reduction
Molecule donates electrons
Nicotinomide adenine dinucleotide (NAD)
Flavin adenine dinucleotide (FAD)
NAD + 2H+  NADH + H+
FAD + 2H+  FADH2

27. Production of Lactic Acid
Normally, O2 is available in the mitochondria to accept H+ (and electrons) from NADH produced in glycolysis
In anaerobic pathways, O2 is not available
H+ and electrons from NADH are accepted by pyruvic acid to form lactic acid

28. Conversion of Pyruvic Acid to Lactic Acid

29. Aerobic ATP Production
Krebs cycle (citric acid cycle)
Completes the oxidation of substrates and produces NADH and FADH to enter the electron transport chain
Electron transport chain
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

30. 3 Stages of Oxidative Phosphoryl-ation

31. The Krebs Cycle

32. Glycogen Breakdown and Synthesis
Glycolysis—Breakdown of glucose; may be anaerobic or aerobic
Glycogenesis—Process by which glycogen is synthesized from glucose to be stored in the liver
Glycogenolysis—Process by which glycogen is broken into glucose-1-phosphate to be used by muscles
Gluco(neo)genesis- formation of glucose from lipids and proteins via intermediates (lactate, pyruvate, amino acids)

33. Relationship Between the Metabolism of Proteins, Fats, and Carbohydrates

34. The Chemiosmotic Hypothesis of ATP Formation

35. Aerobic ATP yield from glucose

36. Summary- Oxidation of Carbohydrate
1. Pyruvic acid from glycolysis is converted to acetyl coenzyme A (acetyl CoA).
2. Acetyl CoA enters the Krebs cycle and forms 2 ATP, carbon dioxide, and hydrogen.
3. Hydrogen in the cell combines with two coenzymes that carry it to the electron transport chain.
4. Electron transport chain recombines hydrogen atoms to produce ATP and water.
5. One molecule of glycogen can generate up to 39 molecules of ATP.

37. Summary (con’t) - Oxidation of Fat
w Lypolysis—breakdown of triglycerides into glycerol and free fatty acids (FFAs).
w FFAs travel via blood to muscle fibers and are broken down by enzymes in the mitochondria into acetic acid which is converted to acetyl CoA.
w Acetyl CoA enters the Krebs cycle and the electron transport chain.
w Fat oxidation requires more oxygen and generates more energy than carbohydrate oxidation.

38. Stop for 10 min break
Any questions?

39. Kilocalorie and other units (SI)
w Energy in biological systems is measured in kilocalories.
w 1 kilocalorie is the amount of heat energy needed to raise 1 kg of water 1°C at 15 °C. 1kcal= 1000cal
Work - energy - application of force through a distance
Should be using SI units
1 Joule (J) = 1 N-m/s2
1 kg-m = 1kg moved through 1 metre
1kcal = 426 kg-m = 4.186kiloJoules (kJ)
1 kJ = kcal ( 1kcal = 4.186kJ)
1 litre of O2 consumed = 5.05kcal= kJ
(1ml of oxygen = .005kcal) - useful conversion factor

40. Power to perform uses up energy- how much oxygen consumption to supply energy?
Power - work/time (Watts or hp)
1hp = 745 watts= 10.7kcal/min
1L of oxygen/min consumption= 5.05kcal/min= 21 kJ/min
1MET = 3.5ml oxygen/kg/min= kcal/kg/min
15 kcal/min= ? Oxygen/min (can you do this?)

41. CARBOHYDRATE vs FAT
1 gram of CHO--> 4 kcal
1 gram of FFA (palmitic acid)--> 9 kcal

42. Body Stores of Fuels and Energy
g kcal
Carbohydrates grams kcal
Liver glycogen
Muscle glycogen ,025
Glucose in body fluids
Total 375 1,538
Fat
Subcutaneous 7,800 70,980
Intramuscular ,465
Total 7,961 72,445
Note. These estimates are based on an average body weight of 65 kg (143 lb) with 12% body fat.

43. Oxygen consumption for Carbohydrate (glucose from glycogen)
(C6H1206)n + 6 O2 --> 6 CO2 +6 H ATP
6 moles of O2 needed to break down 1 mole of glycogen
6 moles x 22.4 l/mole oxygen = l
134.4l/39 moles of ATP = l/mole ATP
at rest takes about min,
during max exercise takes about 1 min
ratio (RQ) carbon dioxide/oxygen = 6/6 = 1

44. Aerobic ATP yield from FFA (free fatty acid - palmitic acid (16C)
16C  7 Acyl coA  7 acetyl coA
(C16H3202) + 23 O2 --> 16 CO2 +16 H ATP
23 moles of O2 needed to break down 1 of palmitic acid
23 moles x 22.4 l/mole oxygen = l
512l/130 moles of ATP = l O2/mole ATP
ratio of carbon dioxide/oxygen = 16/23 = 0.7
15% more oxygen than metabolising glycogen, but advantage is light weight (little water) storage

45. How do we determine efficiency of ox phos- respiration (metabolism of glucose)?
38moles ATP x 7.3kcal/mole ATP
686 kcal/mole glucose
= 0.4 x100% = 40% (60% lost heat)
how does this compare to mechanical engine?

46. Control of Bioenergetics
Rate-limiting enzymes
An enzyme that regulates the rate of a metabolic pathway
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

47. Action of Rate-Limiting Enzymes

48. Control of Metabolic Pathways

49. 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

50. Maximal capacity and power of three energy systems
System moles ATP/min power capacity
phosphagen
anaerobic glycolysis
aerobic (from glycogen)
at rest - aerobic system supplies ATP with oxygen consumption about 0.3L/min, blood lactate remains constant

51. Contribution of energy systems

52. Rest-to-Exercise Transitions
Oxygen uptake increases rapidly
Reaches steady state within 1-4 minutes
Oxygen deficit
Lag in oxygen uptake at the beginning of exercise
Suggests anaerobic pathways contribute to total ATP production
After steady state is reached, ATP requirement is met through aerobic ATP production

53. The Oxygen Deficit

54. Differences in VO2 Between Trained and Untrained Subjects- Why?

55. Recovery From Exercise: Metabolic Responses
Oxygen debt
Elevated VO2 for several minutes immediately following exercise
Excess post-exercise oxygen consumption (EPOC)
“Fast” portion of O2 debt
Resynthesis of stored PC
Replacing muscle and blood O2 stores
“Slow” portion of O2 debt
Elevated body temperature and catecholamines
Conversion of lactic acid to glucose (gluconeogenesis)

56. Oxygen Deficit and Debt During Light-Moderate and Heavy Exercise

57. Factors Contributing to EPOC

58. Metabolic Response to Exercise: Short-Term Intense Exercise
High-intensity, short-term exercise (2-20 seconds)
ATP production through ATP-PC system
Intense exercise longer than 20 seconds
ATP production via anaerobic glycolysis
High-intensity exercise longer than 45 seconds
ATP production through ATP-PC, glycolysis, and aerobic systems

59. Metabolic Response to Exercise: Prolonged Exercise
Exercise longer than 10 minutes
ATP production primarily from aerobic metabolism
Steady state oxygen uptake can generally be maintained
Prolonged exercise in a hot/humid environment or at high intensity
Steady state not achieved
Upward drift in oxygen uptake over time

60. Metabolic Response to Exercise: Incremental Exercise
Oxygen uptake increases linearly until VO2max is reached
No further increase in VO2 with increasing work rate
Physiological factors influencing VO2max
Ability of cardiorespiratory system to deliver oxygen to muscles
Ability of muscles to take up the oxygen and produce ATP aerobically

61. Changes in Oxygen Uptake With Incremental Exercise- explain?

62. Estimation of Fuel Utilization During Exercise- from overall equations
Respiratory exchange ratio (RER or R)
VCO2 / VO2
Indicates fuel utilization
0.70 = 100% fat
0.85 = 50% fat, 50% CHO
1.00 = 100% CHO
During steady state exercise
VCO2 and VO2 reflective of O2 consumption and CO2 production at the cellular level

63. Exercise Intensity and Fuel Selection
Low-intensity exercise (<30% VO2max)
Fats are primary fuel
High-intensity exercise (>70% VO2max)
CHO are primary fuel
“Crossover” concept
Describes the shift from fat to CHO metabolism as exercise intensity increases
Due to:
Recruitment of fast muscle fibers
Increasing blood levels of epinephrine

64. Illustration of the “Crossover” Concept

65. Exercise Duration and Fuel Selection
During prolonged exercise there is a shift from CHO metabolism toward fat metabolism
Increased rate of lipolysis
Breakdown of triglycerides into glycerol and free fatty acids (FFA)
Stimulated by rising blood levels of epinephrine

66. Shift From CHO to Fat Metabolism During Prolonged Exercise

67. Interaction of Fat and CHO Metabolism During Exercise
“Fats burn in the flame of carbohydrates”
Glycogen is depleted during prolonged high-intensity exercise
Reduced rate of glycolysis and production of pyruvate
Reduced Krebs cycle intermediates
Reduced fat oxidation
Fats are metabolized by Krebs cycle

68. Sources of Fuel During Exercise
Carbohydrate
Blood glucose
Muscle glycogen
Fat
Plasma FFA (from adipose tissue lipolysis)
Intramuscular triglycerides
Protein
Only a small contribution to total energy production (only ~2%)
May increase to 5-15% late in prolonged exercise
Blood lactate
Gluconeogenesis in liver

69. Effect of Exercise Intensity on Muscle Fuel Source
What does this graph show?

70. Effect of Exercise Duration on Muscle Fuel Source- summarise

71. Summary Aerobic and anaerobic systems
What regulates metabolic pathways?
What is the RER?
Describe how fuel utilisation is affected by intensity and duration of exercise
What happens during recovery from exercise?
A note about ATP yield- some sources say 38 some say 36 with aerobic resp