Selective reabsorption (CIE International A-level Biology)

This lesson has been written to cover the 2nd part of specification point 14.1 (f) of the CIE International A-level Biology specification which states that students should be able to describe how the process of selective reabsorption is involved in the formation of urine. It has specifically been designed to build on the knowledge gained in the previous lessons on the structure of the nephron and ultrafiltration.

The lesson begins by challenging the students to recall the substances that are found in the glomerular filtrate so that each of them can be considered over the course of the rest of the lesson. Moving forwards, the first of the numerous discussion points which are included in the lesson is used to get students to predict the component of the filtrate which won’t be found in the urine when they are presented with pie charts from each of these situations. Upon learning that glucose is 100% reabsorbed, along with most of the ions and some of the water, the rest of the lesson focuses on describing the relationship between the structure of the PCT and the function of selective reabsorption. Again, this section begins by encouraging the students to discuss and to predict which structures they would expect to find in a section of the kidney if the function is to reabsorb. They are given the chance to see the structure (as shown in the cover image) before each feature is broken down to explain its importance. Time is taken to look at the role of the cotransporter proteins to explain how this allows glucose, along with sodium ions, to be reabsorbed from the lumen of the PCT into the epithelial cells. The final part of the lesson focuses on urea and how the concentration of this substance increases along the tubule as a result of the reabsorption of some of the water.

This lesson has been designed for students studying on the CIE International A level Biology course and ties in closely with the other lessons on the kidney