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 + H2O ↔ 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: 18-20 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, aa3, 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: ~80-100 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:
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Glycolysis: catabolism of glucose
Glycogenolysis: catabolism of glycogen
Gluconeogenesis: form new glucose
Glucogenesis: form new glycogen
Glucagon: hormone
Glygolysis/Embden-Myerhoff
pathway
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occurs in the cytosol
net 2 ATP
Glucose must be transported into the cell
4 glucose transporters:
– Glut 1
– Glut 2
Glut 3
Glut 4
 Glut 4 is in skeletal muscle
Fate of glucose and ratio of
lactate to pyruvate depends on:
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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 malateaspartate shuttle
FADH is shuttled via glycerolphosphate 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