Blood lactate levels before, during and after exercise were monitored of an athl
ID: 266285 • Letter: B
Question
Blood lactate levels before, during and after exercise were monitored of an athlete training for a 400 m sprint. The concentrations of lactate in this athlete’s blood plasma during a 400 m spring elevated from 15 uM to 170 uM within the first 10 seconds of running. During 10-50 seconds of the race, the lactate levels declined slowly reaching 40 uM after completion of the sprint.
(a) What caused the rapid rise in lactate concentration in the beginning of the race? (4 points)
(b) What caused the decline in lactate concentration and why did the decline occur slower than the increase? (4 points)
(c) The resting lactate concentration was 15 uM. Why it was not zero at resting? (4 points)
(d) Patients with defects in fructose 1,6-biphophatase results in very high levels of lactate in blood plasma. Explain this observation. (4 points)
(e) Experienced runners do not consume large amounts of glucose before a marathon. Based on your knowledge on insulin level changes after a meal, what is the biochemical basis for runners avoiding this fuel? (4 points)
Explanation / Answer
Please find the answers below:
Part a: Lactate represents a product of rapid anaerobic respiration which instantly replenishes the muscles of energy when required. Since large amount of energy during sprint, lactate levels increased
Part b: Lactate accumulation causes the muscles to fatigue and since lactate remains in irreversible equilibrium with the inorganic phosphate, it is slowly cleared off the system
Part c: A small amount of anaerobic respiration always continues in the muscles to ensure uninterrupted energy supply, hence lactate is alwaya present in the system
Part d: The enzyme fructose biphosphatase is essentially required to conduct aerobic respiration by glycolysis. Hence, failure of this enzyme causes hightened lactate metabolism and its products accumulation by anaerobic respiration
Part e: Long running requires large amountbof energy which generally comes from lactate metabolic process. Since insulin levels are heightened as soon as glucose is increased, it will make the system devoid of any energy substrate and hence the runner would fatigue. Thus, runners generally avoid this energy fuel before exercise.