1. Aerobic and Anaerobic Forms of Metabolism

2. Exercise and energy Energy is needed for all exercises
ATP, the most important molecule carrying energy, can be stored in small amount but is not exchange à need to be made on a constant

3. Mechanisms of ATP production
4 major sets of reactions in aerobic catalysis:
Glycolysis
Krebs cycle
Electron transport chain (ETC)
Oxidative phosphorylation
All 3 major categories of food can be degraded through these processes

5. Electron transport chain

6. Net results from glycolysis and Krebs cycle
1 glucose + 2 ADP + 2 NAD + 2 P à
2 pyruvic acid + 2 ATP + 2 NADH+ + 2 H2O
Krebs cycle
2 pyruvic acid + 6 NAD + 2 FAD à
8 NADH+ + 2 FADH + 2 GTP + 6 CO2
Electron Transport Chain (ETC)
NADH+ + ADP + ½ O2 à NAD + 3 ATP + H2O
FADH + ADP + ½ O2 à FAD + 2 ATP + H20
Oxidative phosphorylation
ADP + Pi à ATP

7. P/O ratio = expresses the yield of ATP formation by oxidative phosphorylation (OP) per atom of O2 reduced to H2O
If complete coupling between ETC and OP: 3 ATP formed
If completely uncoupled: 0 ATP
During uncoupling, NAD and FAD are formed but instead of ATPs formed, heat is produced à used by mammals to produce heat during cold seasons and a mean to control weight.
Max of 34 ATPs from OP
Additional ATPs from substrate phosphorylation
Total ATPs = 40-2 = 38

8. Consequences of O2 deficiency
Lack of O2 à ETC becomes fully reduced and is blocked à no ATP, no NAD and FAD regenerations
Some tissues can generate some ATP without O2 à anaerobic glycolysis
Formation of lactic acid and regeneration of NAD
Muscles can do that, not brain
Net production of 2 ATP / glucose

9. Mammalian brains use ATP much faster than can be produced anaerobically à these brains must have O2!
If no ATP à Na+ K+ pump, Ca++ pump do not function à neurons destroyed

10. Fates of catabolic end-products
Aerobic glycolysis:
Glucose is fully degraded à CO2 + H2O production à respiration
Anaerobic end-products: lactic acid:
molecule still rich in energyà wasteful to eliminate
But too toxic to retain in large amount
Anaerobic conditions are usually short à possibility to use lactic acid later

11. Vertebrates can metabolize lactic acid
Gluconeogenesis
(6 ATP + O2 used)
Or full oxidation to CO2 + H2O and 36 ATP formation

12. Steady / Non-steady state
Steady-state mechanism of ATP production if:
1. ATP produced as fast as it is used
2. uses raw materials no faster than it is replenished
3. chemical by-products voided as fast as produced
4. cell remains in homeostatic equilibrium
Non-steady state:
ATP is consumed faster than it is produced
Wastes are accumulating faster than they can be eliminated
Ex: phosphagen system

13. Patterns of Energy Use
Sustained or short burst
Mild or Strenuous

14. Patterns of Energy Use During sustained exercise: - ATP is consumed
- when the ATP stores are down, use of the phosphagen compounds
- creatinine phosphate found in vertebrate muscle,
- arginine phosphate in invertebrates
Then, ATP is aerobically synthesized from fatty-acids and/or glucose
Muscles are especially geared to use fatty- acids à derived from fat (triglycerides through b-oxidation in the liver)
Glucose is used or synthesized from glycogen reserves

15. Aerobic ATP synthesis needs….. O2!
If the exercise is strenuous, the O2 store might not be adequate to support this synthesis
Then, the body has no choice but to turn to anaerobic glycolysis à less efficient ATP synthesis + lactic acid accumulation

16. Muscle fatigue and return to resting state
Many causes:
Lack of O2 in the muscle or in the blood
Lack of glucose or glycogen store
Accumulation of lactic acid
Accumulation of calcium ions in inappropriate cell compartments

17. Mechanisms of ATP production and use
Mode of operation
ATP yield
ATP rate - production at onset
ATP rate - production
Return to normal
Aerobic catabolism using pre- existing O2
Non steady
Small
Fast
High
Aerobic catabolism
Steady
Slow
Moderate
------
Phosphagen use
Anaerobic glycolysis
Moderate - small

18. Muscle fiber types Slow oxidative (SO) Fast glycolytic (FG)
Rich in mitochondria
High level of enzymes involvd in oxidative pathways
Muscle rich in blood vessels and myoglobin à red color
Fast glycolytic (FG)
Rich in ATPase
Less blood vessels, mitochondria à white color

21. Uses of energy in animals ??
Birds during migration
Lobsters during escape behavior (short burst of tail muscle contraction)
Salmons during upstream migration
Antelope during escape run

22. Response to decreased O2 in environment
Shut-down metabolism à dormancy (brine- shrimp embryo
Diving animals: dive long enough to use O2 store and/or use anaerobic glycolysis à lactic acid use à must be eliminated prior to next dive

23. Some animals (diving turtles) can sustain long periods without oxygen:
Uses metabolic depression to maintain brain tissue integrity
Turtles become comatose, accumulate large store of lactic acid

24. ATP synthesis under reduced O2 availability
O2 regulation: steady rate of O2 consumption and ATP synthesis despite changing level of O2. possible only over a certain range of [O2]
O2 conformity: O2 rate of consumption falls with O2 in environment

25. Water-breathing anaerobes
Uncommon: some clams, mussels, worms, some goldfishes à buried in marsh sediments (no O2)
Strategy to survive anoxia:
metabolic depression
ATP synthesis through acetic, succinic, proprionic acids and alanine synthesis à excreted in environment à less acidity

26. Anaerobiosis in goldfish and crucian carp
These fishes synthesize LDH à lactic acid formation
Muscles can convert lactic acid to ethanol + CO2
Consequences?