Answer:
At the beginning, aerobic respiration is used by his legs to generate energy when there was still sufficient oxygen intake for energy to be generated via oxidative phosphorylation.
Towards the end of the ride, his legs are generating energy through anaerobic respiration due to insufficient oxygen intake to keep up with the energy requirement of his muscles as he cycles continuously. Through anaerobic respiration, pyruvate from glycolysis is converted to lactate by lactate dehydrogenase instead of being channelled to the mitochondria for oxidative phosphorylation. The accumulation of lactate in his muscles is what causes the pain in his leg. After he stops the activity, the pain would reduce as lactate is transported to the liver to be reconverted back into pyruvate.
Answer:
In the given case, the brain of the alien would be showing an enlarged region with surface grooves and folds. It is nothing but the cerebral cortex and mainly the neocortex. As the name suggests that it is the latest addition to the brain and is regarded to be originated by the process of evolution.
It is the main region of extraordinary cognitive tendencies like reasoning, thinking, analysis, and other things. As mentioned in the question, that alien is trained like astronauts on the Earth, thus, this neocortex would be certainly found in the brain of the alien.
40%........so if ya weigh a lot, pray that you are strong!
