The Equator is halfway in between
Answer:
A. If the aerobic pathway—cellular respiration—cannot meet the energy demand, then the anaerobic pathway—lactic acid fermentation—starts up, resulting in lactic acid buildup and "oxygen debt."
D. The rate of energy demand determines how the muscles will obtain energy, either from cellular respiration or from lactic acid fermentation if not enough oxygen is present.
Explanation:
It is important to consider that Kenny hikes all day but at a steady pace, whereas Janelle runs very fast. So Kenny's case, the supply of oxygen is sufficient to maintain aerobic respiration within the muscle cells. During this process only CO2, Water, and ATP are produced; therefore, there is no oxygen debt. We should keep in mind that the body shifts to anaerobic metabolism only when the supply of oxygen is limited.
In Janelle's case, running fast would need energy at higher rates and the supply of oxygen would not be sufficient to generate a high amount of ATPs. Therefore, to compensate for this deficiency, cells will start fermenting glucose to lactic acid and produce ATP and maintain energy demands. This lactic acid causes fatigue and this is why Janelle has aching and breathing hard. Breathing hard is also automatic reflux to inhale more oxygen and meet oxygen demands but even breathing hard would not be able to make it and the body will shift to anaerobic respiration automatically.
