In the last step of the ETC, Oxygen is used as the final electron acceptor. Where did this oxygen come from?

answer; both surfaces of the membrane are nonpermeable

hello, ballerbaby1265. i would say that the child has had a concussion due to the fall and their symptoms. 60 beats per minute is normal in a child that is sleeping, but not while awake. two of the main symptoms of a concussion after are both sleepiness and being tired. i hope i have a great night.