This is because hydrogen ions are __secreted/reabsorbed__ from the _________ and the _____________. The hydrogen ions move across the apical cell membrane into the filtrate by ____________ in the PCT and by _________________ in the DCT. As the hydrogen ions are being secreted, _____________ is being reabsorbed. What is the osmolarity of plasma? What is the osmolarity of the filtrate at the beginning of the proximal convoluted tubule? At the end of the PCT? At the bottom of the loop of Henle? At the beginning if the DCT? At the end of the DCT? At the end of the collecting duct (if ADH is present)? If ADH is not present, will the osmolarity of the urine become higher or lower?