Final answer:
The pain experienced while running away from an angry dog due to unusual exertion is caused by lactic acid fermentation, an anaerobic energy-producing process in muscles that leads to the buildup of lactic acid and a burning sensation. Option a is correct answer.
Step-by-step explanation:
If you are running away from an angry dog and exerting yourself beyond your usual capacity, the pain you feel can be associated with lactic acid fermentation. This is a biological process that takes place in your muscle cells when they are low on oxygen due to intense activity. The muscles switch to generating energy using an anaerobic pathway known as lactic acid fermentation, which allows the production of ATP, the energy currency of the cell, without oxygen.
The reaction involved is: Pyruvic acid + NADH → lactic acid + NAD+. The enzyme responsible for this reaction is lactate dehydrogenase (LDH). However, during this process, lactic acid builds up in the muscles, which can cause a sensation of burning and soreness. Although lactic acid itself is not solely responsible for muscle fatigue and was once over-emphasized as the cause of soreness, the increase in acidity within the muscle due to lactic acid buildup can still contribute to the discomfort you experience.
Continued effort under these conditions leads to further accumulation of lactic acid, more acidity in the muscles, and increased discomfort. Once your muscles rest and oxygen supply is restored, lactic acid can be transported away from the muscles and converted back to pyruvate in the liver, relieving the pain and discomfort.