During cellular respiration, OXYGEN serves as an electron acceptor and Adenosine triphosphate (ATP) is produced. during photosynthesis, WATER serves as an electron donor and oxygen molecules, hydrogen ions and electrons are produced.
An exoskeleton is found in _Molluscs and Arthropods__; an endoskeleton is found in _____sponges, echinoderms, and vertebrates. __.