Three Energy Systems  ATP regenerated by PCr  Oxidative Phosphorylation  Glycolysis

ATP (adenosine triphosphate)  remove one phosphate bond from ATP, have ADP adenosine diphosphate  loss of second - AMP, adenosine monophosphate

ATP + H 2 O ↔ ADP + P via ATPase

ATP is located throughout the cytoplasm and nucleoplasm of all cells

Creatine Phosphate (CP) (or Phosphocreatine PCr )  high energy phosphate, a donor of P to ADP  PCr + ADP + H → Cr + ATP via CPK (creatine phosphokinase or creatine kinase )

Rapid resynthesis of ATP, nonaerobic

3-4 X more PCr than ATP  ATP: 2-6 mmol/kg  PCr: mmol/kg  PCr is high energy phosphate reservoir

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

When both ATP and PCr stores are depleted :  Two ADP can form one ATP via adenylate kinate (myokinase in muscle)

Phosphorylation  transfer of energy in the form of phosphate bonds  energy for this is from cellular oxidation of substrates

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

Cellular Oxidation  transfer of electrons for hydrogen to oxygen  result from metabolism of substrates CHO,fat, protein  during metabolism, H ions are removed from these substrates and carried by carrier molecules to the mitochondria, where the electron transport system resides

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

 energy potential is decreased as the hydrogen ions are removed (to bind with oxygen to make water)  only the last cytochrome, aa 3, can release the hydrogen directly to the oxygen

Oxidative Phosphorylation and Electron Transport are separate, but linked

P/O ratio  reflects the coupling of ATP production to the electron transport  NADH P/O ratio = 3, FADH P/O ratio = 2

Continuous Resynthesis of ATP  donor electrons (NADH, FADH), reducing agent  oxygen as electron acceptor  enzymes for pathway

CHO: primary function: fuel  only macronutrient that can generate ATP anaerobically  during light to moderate intensity: 1/2 the energy requirement  need CHO to feed “flame” of fat catabolism (CHO flame)

 human skeletal muscle: ~ mM of glycogen/kg of wet wt (15-18 g of glycogen)  70 kg male: ~400 g of muscle glycogen in whole muscle pool  5-6 g of glucose available in blood  liver: ~50-90 g of available glycogen

Release of glucose  blood glucose concentrations  hormonal interactions: insulin, glucagon, norepinephrine, epinephrine (catacholamines)

Review of Terms:  Glycolysis: catabolism of glucose  Glycogenolysis: catabolism of glycogen  Gluconeogenesis: form new glucose  Glucogenesis: form new glycogen  Glucagon: hormone

Glygolysis/Embden-Myerhoff pathway  occurs in the cytosol  net 2 ATP  Glucose must be transported into the cell  4 glucose transporters: –Glut 1 Glut 3 –Glut 2 Glut 4  Glut 4 is in skeletal muscle

Fate of glucose and ratio of lactate to pyruvate depends on:  enzyme kinetics  mitochondrial capacity of cell  hormonal control  oxygen availability  required rate of energy production and energy needs

Gycolysis regulation  Hexokinase  Phosphofructokinase  Pyruvate Kinase (liver, not sk. mu.)

NADH must be shuttled to mitochondria via malate- aspartate shuttle

FADH is shuttled via glycerol- phosphate shuttle

Glucose Paradox  liver prefers to make GLYCOGEN from lactate rather than from glucose  glucose is available to the rest of the body (brain, cns, skeletal muscle)

LDH is in competition with mitochondria for pyruvate

LDH: two types  heart  muscle: high affinity for pyruvate, higher biological activity than H type  5 isozymes