Three Energy SystemsThree Energy Systems

ATP regenerated by PCrATP regenerated by PCr Oxidative PhosphorylationOxidative Phosphorylation GlycolysisGlycolysis

ATP (adenosine triphosphate)ATP (adenosine triphosphate)

remove one phosphate bond from ATP, remove one phosphate bond from ATP, have ADP adenosine diphosphatehave ADP adenosine diphosphate

loss of second - AMP, adenosine loss of second - AMP, adenosine monophosphatemonophosphate

ATP + HATP + H22O O ↔↔ ADP + P via ADP + P via

ATPaseATPase

ATP is located throughout the ATP is located throughout the cytoplasm and nucleoplasm of cytoplasm and nucleoplasm of

all cellsall cells

Creatine Phosphate (CP) (or Creatine Phosphate (CP) (or Phosphocreatine PCr )Phosphocreatine PCr )

high energy phosphate, a donor of P to ADPhigh energy phosphate, a donor of P to ADP PCr + ADP + H PCr + ADP + H →→ Cr + ATP via CPK Cr + ATP via CPK

(creatine phosphokinase or creatine kinase )(creatine phosphokinase or creatine kinase )

Rapid resynthesis of ATP, Rapid resynthesis of ATP, nonaerobicnonaerobic

3-4 X more PCr than ATP3-4 X more PCr than ATP

ATP: 2-6 mmol/kgATP: 2-6 mmol/kg PCr: 18-20 mmol/kgPCr: 18-20 mmol/kg PCr is high energy phosphate reservoirPCr is high energy phosphate reservoir

Intramuscular Stores can only Intramuscular Stores can only last for about 10 sec. during last for about 10 sec. during

maximal workmaximal work

When both ATP and PCr When both ATP and PCr stores are depleted :stores are depleted :

Two ADP can form one ATP via adenylate Two ADP can form one ATP via adenylate kinate (myokinase in muscle)kinate (myokinase in muscle)

PhosphorylationPhosphorylation

transfer of energy in the form of phosphate transfer of energy in the form of phosphate bondsbonds

energy for this is from cellular oxidation of energy for this is from cellular oxidation of substratessubstrates

Oxidative PhosphorylationOxidative Phosphorylation

formation of ATP from ADP and Pi in formation of ATP from ADP and Pi in association with the transfer of electrons association with the transfer of electrons from fuel molecules to coenzymes to from fuel molecules to coenzymes to oxygen (aka cellular oxidation)oxygen (aka cellular oxidation)

occurs in the mitochondriaoccurs in the mitochondria

Cellular OxidationCellular Oxidation

transfer of electrons for hydrogen to oxygen transfer of electrons for hydrogen to oxygen result from metabolism of substrates result from metabolism of substrates

CHO,fat, proteinCHO,fat, protein during metabolism, H ions are removed from during metabolism, H ions are removed from

these substrates and carried by carrier these substrates and carried by carrier molecules to the mitochondria, where the molecules to the mitochondria, where the electron transport system resideselectron transport system resides

Electron Transport ChainElectron Transport Chain

NADNAD++ (nicotinamide adenine (nicotinamide adenine dinucleotid) and FAD (flavin adenine dinucleotid) and FAD (flavin adenine dinucleotide) are the electron dinucleotide) are the electron (hydrogens) acceptors to be passed (hydrogens) acceptors to be passed down the ETC “bucket brigade” to down the ETC “bucket brigade” to coenzyme Q, to the cytochromescoenzyme Q, to the cytochromes

energy potential is decreased as the energy potential is decreased as the hydrogen ions are removed (to bind with hydrogen ions are removed (to bind with oxygen to make water)oxygen to make water)

only the last cytochrome, aaonly the last cytochrome, aa33, can release , can release

the hydrogen directly to the oxygenthe hydrogen directly to the oxygen

Oxidative Phosphorylation Oxidative Phosphorylation and Electron Transport are and Electron Transport are

separate, but linkedseparate, but linked

P/O ratioP/O ratio

reflects the coupling of ATP production to reflects the coupling of ATP production to the electron transportthe electron transport

NADH P/O ratio = 3, FADH P/O ratio = 2NADH P/O ratio = 3, FADH P/O ratio = 2

Continuous Resynthesis of ATPContinuous Resynthesis of ATP

donor electrons (NADH, FADH), reducing donor electrons (NADH, FADH), reducing agentagent

oxygen as electron acceptoroxygen as electron acceptor enzymes for pathwayenzymes for pathway

CHO: primary function: fuelCHO: primary function: fuel

only macronutrient that can generate ATP only macronutrient that can generate ATP anaerobicallyanaerobically

during light to moderate intensity: 1/2 the during light to moderate intensity: 1/2 the energy requirementenergy requirement

need CHO to feed “flame” of fat catabolism need CHO to feed “flame” of fat catabolism (CHO flame)(CHO flame)

human skeletal muscle: ~80-100 mM of human skeletal muscle: ~80-100 mM of glycogen/kg of wet wt (15-18 g of glycogen)glycogen/kg of wet wt (15-18 g of glycogen)

70 kg male: ~400 g of muscle glycogen in 70 kg male: ~400 g of muscle glycogen in whole muscle poolwhole muscle pool

5-6 g of glucose available in blood5-6 g of glucose available in blood liver: ~50-90 g of available glycogenliver: ~50-90 g of available glycogen

Release of glucoseRelease of glucose

blood glucose concentrationsblood glucose concentrations hormonal interactions: insulin, glucagon, hormonal interactions: insulin, glucagon,

norepinephrine, epinephrine norepinephrine, epinephrine (catacholamines)(catacholamines)

Review of Terms:Review of Terms:

Glycolysis: catabolism of glucoseGlycolysis: catabolism of glucose Glycogenolysis: catabolism of glycogenGlycogenolysis: catabolism of glycogen Gluconeogenesis: form new glucoseGluconeogenesis: form new glucose Glucogenesis: form new glycogenGlucogenesis: form new glycogen Glucagon: hormoneGlucagon: hormone

Glygolysis/Embden-Myerhoff Glygolysis/Embden-Myerhoff pathwaypathway

occurs in the cytosoloccurs in the cytosol net 2 ATPnet 2 ATP Glucose must be transported into the cellGlucose must be transported into the cell 4 glucose transporters:4 glucose transporters:

– Glut 1 Glut 3Glut 1 Glut 3– Glut 2 Glut 4Glut 2 Glut 4

Glut 4 is in skeletal muscleGlut 4 is in skeletal muscle

Fate of glucose and ratio of Fate of glucose and ratio of lactate to pyruvate depends on:lactate to pyruvate depends on:

enzyme kineticsenzyme kinetics mitochondrial capacity of cellmitochondrial capacity of cell hormonal controlhormonal control oxygen availabilityoxygen availability required rate of energy production and required rate of energy production and

energy needsenergy needs

Gycolysis regulationGycolysis regulation

HexokinaseHexokinase PhosphofructokinasePhosphofructokinase Pyruvate Kinase (liver, not sk. mu.)Pyruvate Kinase (liver, not sk. mu.)

NADH must be shuttled to NADH must be shuttled to mitochondria via malate-mitochondria via malate-

aspartate shuttleaspartate shuttle

FADH is shuttled via glycerol-FADH is shuttled via glycerol-phosphate shuttlephosphate shuttle

Glucose ParadoxGlucose Paradox

liver prefers to make liver prefers to make GLYCOGEN GLYCOGEN from from lactatelactate rather than from glucose rather than from glucose

glucose is available to the rest of the body glucose is available to the rest of the body (brain, cns, skeletal muscle)(brain, cns, skeletal muscle)

LDH is in competition with LDH is in competition with mitochondria for pyruvatemitochondria for pyruvate

LDH: two typesLDH: two types

heartheart muscle: high affinity for pyruvate, higher muscle: high affinity for pyruvate, higher

biological activity than H typebiological activity than H type 5 isozymes5 isozymes