A-LevelBiologyHomeostasis9700/42 · Feb/Mar 2024 · Q18 Marks

Fig. 1.1 is a diagram of a nephron. [Figure 1.1]

(a)Label Fig. 1.1 using: • one labelling line and the letter A to identify a region that contains urine • one labelling line and the letter B to identify a region that contains podocytes • one labelling line and the letter C to identify a region of the nephron that is within the medulla of the kidney • one labelling line and the letter D to identify the afferent arteriole.[4]
(b)The cells of the proximal convoluted tubule are adapted to carry out selective reabsorption. Describe and explain how these cells are adapted to carry out selective reabsorption.[4]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2024). The mark or mark type is shown in brackets.

[1] A - label line to collecting duct ;
[1] B - label line to inner part of Bowman's capsule ;
[1] C - label line to, loop of Henle / part of collecting duct below level of convoluted tubules ;
[1] D - label line to wider blood vessel entering Bowman's capsule ;
[1] microvilli, for large surface area/increases surface area (for reabsorption) ;
[1] cotransporter (proteins) for movement of, glucose / amino acids (with sodium ions);
[1] tight junctions / described, to, stop substances passing in between cells / cause substances to pass though cells ;
[1] many mitochondria to provide ATP for, active transport / pumping of Na+ ;
[1] folded basal membrane for many sodium (potassium) pumps;

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