(a)[2]
On Fig. 8.1, use label lines and letters to show: C, the site of the cotransporter proteins; P, the site of the sodium-potassium pumps.
(b)[5]
Explain how the cells of the proximal convoluted tubule are adapted for selective reabsorption.
(c)[2]
Table 8.1 gives the percentage composition of plasma, glomerular filtrate and urine. Because of the action of the cells of the proximal convoluted tubule, glucose and amino acids have been reabsorbed into the blood, whereas only part of the urea has been reabsorbed. Calculate how many times greater the percentage composition of urea is in the urine than in the glomerular filtrate. Show your working and give your answer to the nearest whole number.