Osmoregulation and ADHEdexcel International A Level Biology: Flashcards

What these 14 flashcards ask

What are two adaptations of proximal convoluted tubule cells for reabsorption?
What does the sodium–potassium pump do in PCT cells?
How is glucose reabsorbed in the PCT?
What proportion of glucose is normally reabsorbed?
What is the function of the loop of Henle?
What does the ascending limb do?
What does the descending limb do?
Why do desert mammals have long loops of Henle?
Which part of the brain detects the water potential of the blood?
Which gland releases ADH?
What does ADH do at the collecting duct?
What urine is produced when ADH is high?
What urine is produced when ADH is low?
Why is osmoregulation an example of negative feedback?

Exam questions on Osmoregulation and ADH

A student eats a very salty meal at lunchtime and drinks very little water for the rest of the afternoon. Later, a blood test shows that the water potential of her blood plasma has become more negative than normal.
Predict the effect on the urine that the student produces and explain how this restores her blood water potential.2 marks
A pharmacology student is studying a drug that stops the sodium-potassium pumps in the membranes on the blood side of the cells lining the proximal convoluted tubule. In a healthy kidney these cells have microvilli on the side facing the filtrate and contain many mitochondria.
Suggest why a person taking this drug would have glucose in the urine.2 marks
The kangaroo rat lives in deserts and rarely drinks. Its kidneys have very long loops of Henle and it produces urine that is about four times more concentrated than human urine. The beaver, which lives in water, has short loops of Henle and produces dilute urine.
Describe how the ascending limb of the loop of Henle helps to produce a low water potential in the tissue fluid of the medulla.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).