BIOL 103 Lecture Notes - Lecture 2: Aquaporin 2, Calpain, Cholestasis
23 Sep 2016
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Similar to digestion in vertebrates, but no pepsin. Answer: ph in human stomach is acidic (acidic ph in stomach is an adaptation for vertebrates that perhaps ate bones). In insects, they have a neutral ph therefore no need for pepsin. After digestion, individual amino acids are absorbed by cells lining the small intestine and then enter the blood. In humans, ammonia is toxic so our cells in the liver immediately converts it into something less toxic urea cycle (has 4-5 steps and its cost: atp) In fishes and other aquatic organisms: can produce and have ammonia because it can be easily removed nitrogenous waste product. However not all sea organisms have this. Answer: they have evolved the production of urea via the urea cycle because it allows them to osmoregulate. They produce urea by having it in their urine as their nitrogenous waste and have it built up in their tissues.
