6 (a) Figure 13 shows a kidney nephron - Edexcel - GCSE Biology - Question 6 - 2020 - Paper 1

As the filtrate moves through the first coiled tubule, glucose is reabsorbed into the bloodstream. Initially, there is a high concentration of glucose (6 millimoles per litre) at the start of the tubule. However, by the time the filtrate reaches the end of the first coiled tubule, the concentration drops to 0 millimoles per litre because most of the glucose has been reabsorbed by active transport mechanisms into the blood. This reabsorption is crucial for maintaining blood glucose levels.

The structure that carries urine from the kidney to the bladder is the ureter.

Both individuals have some protein in their urine. Person A has less protein in their urine compared to person B. The amount of protein in urine from person A varies between 2 and 4 (arbitrary units) across the years, showing a slight increase and then a decrease. In contrast, the amount of protein in urine from person B increases significantly each year, changing from 25 to 106 (arbitrary units), which indicates a worsening condition due to kidney disease.

The twin sister is likely to be a suitable kidney donor because she shares the same genetic makeup as Person B. This reduces the chance of the donated kidney being rejected by the immune system, as the tissues, cells, and antigens are similar. Additionally, the donor can live healthily with only one kidney, making this a viable option for transplantation.