energy metabolism during exercise Flashcards
how is ATP used for muscle contraction
direct fuel for contraction by supplying ATPase activity of myosin
ATP utilisation inc more than 100-fold inc in milliseconds
where does the ATP in muscle come from
at rest muscle has about 5 mmol ATP per Kg wet weight
lasts <2s in vigorous contraction
short term muscle can inc ATP production 20-100 fold - initial main fuel glycogen in muscle tho other tissues need to cooperate to provide fuel in time
muscle metabolism at rest
glycogen stores maintained/replenished
ox metabolism of fatty acids to provide energy for muscle (TCA)
little lactate produced as pyruvate used in TCA/replenish glycogen stores as sufficient O2
how does muscle metabolism change with exercise
glycogenolysis provides fuel source
inc 02 consumption for oxphos
inc blood flow to muscles due to local mediators (NO) and B adrenergic stimulation of VSMCs
amount of energy derived from glycolysis and oxphos depends on intensity and duration of exercise
what role does phosphorylase play in the mobilisation of muscle glycogen during exercise
activated by AMP, acts allosterically
activated by phosphorylation in response to stress hormones and inc cytoplasmic Ca2+ (glycogen mobilisation controlled by Ca2+ levels , also AMP and adrenaline)
what role does glycogen synthase play in the mobilisation of muscle glycogen during exercise
activated allosterically by G6P, low during exercise
inactivated by phosphorylation in response to stress hormones, inc cytoplasmic Ca2+
what role does phosphofructokinase-1 play in the mobilisation of muscle glycogen during exercise
inhibited allosterically by ATP and activated by AMP and Fro-2,6-P
important sensor of energy available and needs during exercise
role of Ca2+ in muscle contraction
inc Ca2+ concentration is a signal for muscle contraction
inc muscle glycogen breakdown by activating glycogen phosphorylase to supply energy required
stimulates production of NO = vasodilation, inc blood flow
characteristics of skeletal muscle blood flow
skeletal muscle 20% CO at rest, 80% extreme exertion
coordinated, rhythmical contractions via skeletal muscle pump mechanism
blood flow determined by local reg (tissue and endothelial) factors eg tissue hypoxia, adenosine, K+, CO2, H+ and NO
vascular B2-Rs = vasodilation (stim by adrenaline)
hormonal control of metabolism during exercise
inc adrenaline - promote glycogen and lipid mobilisation
dec insulin and inc glucagon - glycogenolysis and gluoconeogenesis
no need for insulin for glucose uptake in muscle as contraction activates glut 4
3 systems for forming ATPin muscle
anaerobic
ATP-PC (phosphocreatine, fastest but not a lot of ATP)
Lactic Acid (glycogen, fast but not lots of ATP)
aerobic
oxygen system (glycogen, fats, proteins, slow, lots of ATP)
anaerobic has higher power but smaller capacity
how is PC an extra source of energy in muscle cells
aka creatine phosphate
PC + ADP (creatine kinase) - ATP + creatine
first top up of muscle ATP
rest 100 mmol PC per kg dry weight, vig exercise lasts 16s
anaerobic glycolysis
glycogen breakdown and glycolysis stimulated during contraction
inc rate of metabolism beyond O2 supply, glycolysis proceed anaerobically (less ATP produced and lactate builds up)
even when O2 sufficient, pyruvate can still be formed faster than oxidised, lactate builds up
lactate metabolism via the cori cycle
lactate used by liver to regenerate glucose (via G6P, muscle prod 2ATP and liver uses 6ATP), transferred back to muscle for energy production
insufficient blood flow, lactic acid builds up
aerobic metabolism during exercise
muscle uses FA from adipose tissues (and glycogen via aerobic metabolism of glucose) to maintain ATP
dependant on O2 supply
necessary for FA oxidation
