Biology 9700 · AS & A Level · Homeostasis in mammals
Homeostasis in mammals — practice question
The human kidneys handle $1200\,\text{cm}^3$ of blood each minute. Out of this $1200\,\text{cm}^3$, $700\,\text{cm}^3$ is plasma. When blood flows through the glomeruli in the kidneys, $125\,\text{cm}^3$ of fluid moves into the renal capsules (Bowman’s capsules). This fluid is known as the glomerular filtrate and it is formed by a process named ultrafiltration.
(a(i))[2]
Find the percentage of plasma that enters the renal capsules. Show how you worked it out and round your answer to one decimal place.
(a(ii))[4]
Explain how the glomerular capillaries and the podocytes are structurally adapted for ultrafiltration.
(b(i))[1]
Give the names of the structures labelled X.
(b(ii))[2]
Explain why the epithelial cells of the proximal convoluted tubule contain many mitochondria.
(b(iii))[2]
Each minute, $125\text{ cm}^3$ of glomerular filtrate enters the renal capsules, but only $45\text{ cm}^3$ goes on to the loops of Henlé. Name two substances, other than water, that are reabsorbed into the blood from the proximal convoluted tubule.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The calculation yields $17.9\%$ (accept $17.8\%$)” …