1.1. The glomerulus is a structure in the kidneys responsible for the process of ultrafiltration.  

Explain how ultrafiltration would be affected by severe dehydration.  

1.2. An important role of the kidneys is the removal of urea from the blood. The amount of urea removed from the blood can be used as a measure of the rate of ultrafiltration, also known as the glomerular filtration rate (GFR).  

An individual excretes 540 mg of urea in their urine over the course of 1 hour, and has a blood urea concentration of 0.01 mg cm^-3 entering the kidneys. Use this information to calculate this person’s GFR.  Give your answer in cm³ min^-1.      

1.3. After ultrafiltration, the filtrate travels through the kidney nephron.  Figure 1 shows what happens to various components of the filtrate as they move through the different parts of an individual’s nephron.

Figure 1

Describe and explain the shape of the curve for sodium ions and water as they travel through region 2 of the nephron in Figure 1. 

1.4. Explain how the line for water in region 4 of Figure 1 would look different if the ADH concentration in this individual’s blood decreased.