Overriding
a
block
in
Glycolysis!
(A
clinical
application)
Michael P. was noticeably weak from his birth. He didn't move much, had poor muscle tone and difficulty breathing, and grew exhausted merely from the effort of feeding. At the age of two and a half months, he suffered his first seizure, staring and jerking his limbs for several frightening minutes. Despite medication, his seizures continued, occurring more frequently.
The doctors were puzzled because the results of most of Michael's many medical tests were normal-with one notable exception, His cerebrospinal fluid (the fluid that bathes the brain and spinal cord) was unusually low in glucose and lactic acid. These deficiencies told the physicians that Michael's cells were not performing glycolysis or anaerobic respiration. Hypothesizing that a profound lack of ATP was causing the symptoms, medical researchers decided to intervene beyond the block in the boy's metabolic pathway, taking a detour to energy production. When Michael was seven and a half months old, he began a diet rich in certain fatty acids. Within four days, he appeared to be healthy for the very first time! The diet had resumed aerobic respiration at the point of acetyl coenzyme A formation by supplying an alternative to glucose. Other children with similar symptoms have since enjoyed spectacular recoveries similar to Michael's thanks to the dietary intervention, but doctors do not yet know the long-term effects of the therapy. This medical success story, however, illustrates the importance of the energy pathways-and how valuable our understanding of them can be.
Interesting Facts:
| Lactic acid formation occurs in an interesting variety of circumstances. Coaches measure lactic acid levels in swimmers' and sprinters' blood to assess their physical condition. Lactic acid accumulates to triple the normal levels in the bloodstreams of children who vigorously cry when they are being prepared for surgery but not in children who are calm and not crying. This suggests that lactic acid formation accompanies stress. |
| Human muscle cells that are working so strenuously that their production of pyruvic acid exceeds the oxygen supply begin to produce lactic acid. In this condition of "oxygen debt", the muscle cells are forced to utilize solely the anaerobic pathway, which provides fewer ATPs per glucose molecule than does aerobic respiration. The accumulation of lactic acid contributes to the feeling of muscle fatigue and cramps. Walking after cramping at the end of a race can make a runner feel better by hastening the depletion of lactic acid. |
