aerobic and anaerobic forms of metabolism

Aerobic and Anaerobic Forms of Metabolism

Exercise and energyEnergy is needed for all exercisesATP, the most important molecule carrying energy, can be stored in small amount but is not exchange need to be made on a constant

Mechanisms of ATP production4 major sets of reactions in aerobic catalysis:GlycolysisKrebs cycle Electron transport chain (ETC)Oxidative phosphorylationAll 3 major categories of food can be degraded through these processes

Electron transport chain

Net results from glycolysis and Krebs cycleGlycolysis: 1 glucose + 2 ADP + 2 NAD + 2 P 2 pyruvic acid + 2 ATP + 2 NADH+ + 2 H2OKrebs cycle 2 pyruvic acid + 6 NAD + 2 FAD 8 NADH+ + 2 FADH + 2 GTP + 6 CO2

Electron Transport Chain (ETC) NADH+ + ADP + O2 NAD + 3 ATP + H2O FADH + ADP + O2 FAD + 2 ATP + H20

Oxidative phosphorylation ADP + Pi ATP

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 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

Consequences of O2 deficiencyLack of O2 ETC becomes fully reduced and is blocked no ATP, no NAD and FAD regenerationsSome tissues can generate some ATP without O2 anaerobic glycolysisFormation of lactic acid and regeneration of NADMuscles can do that, not brain

Net production of 2 ATP / glucose

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

Fates of catabolic end-productsAerobic glycolysis: Glucose is fully degraded CO2 + H2O production respiration

Anaerobic end-products: lactic acid:molecule still rich in energy wasteful to eliminateBut too toxic to retain in large amountAnaerobic conditions are usually short possibility to use lactic acid later

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

Steady / Non-steady stateSteady-state mechanism of ATP production if:1. ATP produced as fast as it is used2. uses raw materials no faster than it is replenished3. chemical by-products voided as fast as produced4. cell remains in homeostatic equilibrium

Non-steady state:ATP is consumed faster than it is producedWastes are accumulating faster than they can be eliminatedEx: phosphagen system

Patterns of Energy UseSustained or short burst

Mild or Strenuous

Patterns of Energy UseDuring 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 derived from fat (triglycerides through b-oxidation in the liver)Glucose is used or synthesized from glycogen reserves

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 less efficient ATP synthesis + lactic acid accumulation

Muscle fatigue and return to resting stateMany causes:Lack of O2 in the muscle or in the bloodLack of glucose or glycogen storeAccumulation of lactic acidAccumulation of calcium ions in inappropriate cell compartments

Mechanisms of ATP production and use

Mechanisms of ATP productionMode of operationATP yieldATP rate - production at onsetATP rate - productionReturn to normalAerobic catabolism using pre-existing O2Non steadySmallFastHighFastAerobic catabolismSteadyHighSlowModerate------Phosphagen useNon steadySmallFastHighFastAnaerobic glycolysisNon steadyModerate - smallFastHigh Slow

Muscle fiber typesSlow oxidative (SO)Rich in mitochondriaHigh level of enzymes involvd in oxidative pathwaysMuscle rich in blood vessels and myoglobin red colorFast glycolytic (FG)Rich in ATPaseLess blood vessels, mitochondria white color

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

Response to decreased O2 in environmentShut-down metabolism dormancy (brine-shrimp embryoDiving animals: dive long enough to use O2 store and/or use anaerobic glycolysis lactic acid use must be eliminated prior to next dive

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

ATP synthesis under reduced O2 availabilityO2 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

Water-breathing anaerobesUncommon: some clams, mussels, worms, some goldfishes buried in marsh sediments (no O2)Strategy to survive anoxia: metabolic depressionATP synthesis through acetic, succinic, proprionic acids and alanine synthesis excreted in environment less acidity

Anaerobiosis in goldfish and crucian carpThese fishes synthesize LDH lactic acid formationMuscles can convert lactic acid to ethanol + CO2

Consequences?