Practice: A 45-year-old man with a history of poorly-controlled Type I Diabetes presents to the emergency department complaining of vomiting, abdominal pain, and weakness. He is confused—he does not know the day of the week and is unable to recount how he got to the hospital. He is noted to be breathing abnormally. His blood pH is 7.3. Which of the following correctly identifies the location of the K+/H+ ATPase proteins on the cells whose activity will be increased by this patient’s condition?