Lecture 28 Glycogenolysis.docx

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Michael Baker

BCH210H © Lisa | Page 12 Lecture 28: Glycogenolysis  if pyruvate accumulates as a result of not enough blood (and thus O ) sup2lied to the muscle (bc out of shape), lactate will accumulate and drop pH, making it painful in muscle cramping  NADH will also be converted to NAD  SY recovers and pulls lactate back into pyruvate  nonathletes would lose lactate to the blood and recycled in the liver (but not favourable bc you would be losing this imp fuel)  sufficient O2in mitochondria will allow pyruvate to be recovered from lactate (breathe heavily)  blood has limited reserve for glucose  if glucose level drops, brain and other organs will be very sensitive to his  needs a backup reliable source of fuel—glycogen  glycogen can be broken down (is available in muscle and liver) to serve as a source of NRG and blood glucose  hormones reacting to exercise and level of blood sugar can effect glycogen breakdown mobilization  blood sugar is limited—normally 2mM (fasting)  if lower, may go into hypoglycemia  SY needs fuel—muscle glycogen  glycogen is already right there where it is needed  fat is not as accessible  glycogen breaks down very quickly in tissues (fat, slowly)  if go for a run for only 20min, won’t break down fat, only glycogen  running before breakfast is beneficial bc glycogen stores will be lowered through the night  deal w less glycogen  glycogen is a polymer of glucose  very branched  principally α(1→4), but some α(1→6)  each glucose unit can support glycolysis  breakdown of glycogen supplies muscle w NRG to keep on running  liver glycogen can support blood sugar  glycogen is imp in endurance or strenuous sports  need good glycogen reserves  glycogen is imp to sustain  efficiency for muscle contraction dramatically decreases after glycogen stores run out  can’t use fat effectively  use fat to take drain off glycogen  combination of fuel is imp o need glycogen to last right to the end of the race bc you need that to get the most out of fat as a fuel Endocrine control breakdown of glycogen (Glycogenolysis)  adrenaline (epinephrine) has huge role in muscle contraction  hormone released from adrenal glands  released during stress or exercise (physically or mentally stressed)  regulates breakdown of glycogen in the muscle  epinephrine pathway BCH210H © Lisa| Page 212  binds to receptor on surface of muscle cell (adrenergic receptor)  doesn’t enter cell  this galvanizes a series of rxns inside cell  adrenergic receptors can increase HR in cardiac muscle cells  epinephrine binding can result in raising bp, hypertension  beta blockers block effect of adrenalin on heart muscle adrenergic receptors to decrease bp  adrenaline allows glycogen to be broken down  binding activates adenylase cyclise which converts ATP into a signalling molecule, cAMP (second messenger)
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