A-LevelBiologyHomeostasis9700/42 · May/June 2017 · Q612 Marks

(a) Fig. 6.1 is a diagram of a Bowman’s (renal) capsule of a nephron from a mammalian kidney. [Figure 6.1]

(a)On Fig. 6.1, use label lines and letters to label: E - the efferent arteriole G - the glomerulus P - the region of podocyte cells.[3]
(b)Describe how the structure of the epithelial cells of the proximal convoluted tubule is adapted to carry out selective reabsorption.[5]
(c)Complete the following sentences about osmoregulation. In mammals, the water potential of the blood is constantly monitored by ______________ in the hypothalamus of the brain. When the water potential of the blood decreases, the production of a hormone called ______________ in the cells of the hypothalamus increases. This hormone is released into the blood via the ______________. This causes the kidneys to retain more water until the water potential of the blood returns to the set point. This is an example of a ______________ mechanism.[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 (May/June 2017). The mark or mark type is shown in brackets.

[3] E - pointing to the vessel on the left ; G - pointing to capillaries; P - pointing to the inner epithelium of the capsule ;
[max 5] 1. microvilli ; 2. many mitochondria ; 3. tight junctions / described ; 4. folded, basal membrane / described ; 5. many, transport proteins / cotransporters / pumps ; 6. aquaporins; 7. AVP ; e.g. more ER for increased protein synthesis
[4] osmoreceptors ; ADH/antidiuretic hormone ; posterior pituitary (gland); negative feedback; A homeostatic

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.