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AQA A level biology- Osmoregulation revision papers 2023 with correct questions and answers.docx
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AQA A LEVEL BIOLOGY-OSMOREGULATION REVISION PAPERS
2023 WITH CORRECT QUESTIONS AND
ANSWERS
Where are osmoreceptors located? (Correct Answers) Hypothalamus
When a person is dehydrated, the cell volume of an osmoreceptor decreases. Explain
why (Correct Answers) 1) Water potential of blood will decrease
2) Water moves from osmoreceptors into blood by osmosis
Describe and explain how the secretion of ADH affects urine produced by the kidneys?
(Correct Answers) 1) Permeability of (membrane/cells) to water is increased
2) More water absorbed (from/leaves) distal tubule/ collecting duct
3) Smaller volume of urine
4) Urine becomes more concentrated
Describe how urea is removed from the blood? (Correct Answers) 1) Hydrostatic
pressure
2) Cause ultrafiltration at (bowman's capsule/glomeruli/renal capsule)
3) Through basement membrane
4) Enabled by small size urea molecule
Label a nephron (Correct Answers)
Explain how urea is concentrated in the filtrate? (Correct Answers) 1) Reabsorption of
water by osmosis at the (proximal convoluted tubule/ descending loop of henle)
2) Ions actively transported at the distal convoluted tubule/collecting duct (glucose
creates gradient)
What is urea? (Correct Answers) Urea is a waste product of metabolism that is excreted
by the kidneys in urine.
Describe how ultrafiltration produces glomerular filtrate? (Correct Answers) 1) Blood
pressure/hydrostatic pressure
2) Small molecules (named example)
3) Pass through basement membrane (basement membrane acts as a filter)
4) Protein too large to go through (large molecule) so stays behind
5) Presence of pores in capillaries (podocytes=form a filtration barrier)
, Explain how a lack of insulin affects reabsorption of glucose in the kidneys of a person
who does not secret insulin? (Correct Answers) 1) High concentration of glucose in
blood
2) High concentration in tubule/in filtrate
3) Reabsorbed by (facilitated diffusion/active transport)
4) Requires proteins/carriers
5) These are working at maximum rate (are saturated)
6) Not all glucose is reabsorbed, some is lost in urine
Some desert mammals have long loops of henle and secrete large amounts of ADH.
Explain how these two features are adaptations to living in desert conditions? (Correct
Answers) For general principle;
-More water from filtrate is reabsorbed by osmosis from the collecting duct due to longer
loop of henle.
For loop of henle;
-Sodium or chloride ions are absorbed from filtrate in ascending limb. Gradient
established in medulla (concentration of ions increases down medulla)
For ADH;
-Acts on (collecting duct/DCT/second CT) making cells more permeable, inserting
aquaporin's in plasma membranes
A diabetic and non-diabetic ate the same amount of glucose, one hour later the glucose
concentration in the blood of the diabetic was higher. Explain why? (Correct Answers) In
diabetic person;
-Lack of insulin (reduced sensitivity of cells to insulin)
-Reduced uptake of glucose by (cells/liver/muscles)
-Reduced conversion of glucose to glycogen (glycogenesis)
Why does the urine of a non-diabetic not contain glucose? (Correct Answers) 1) Leaves
blood at kidneys
2) Taken back into the blood where it is reabsorbed in the 1st convoluted tubule (PCT)
A high blood glucose concentration could cause glucose to be present in the urine of a
diabetic person. Suggest how? (Correct Answers) 1) High concentration of glucose in
filtrate
2) Cannot all be reabsorbed (PCT too short to reabsorb all the glucose)
Explain why a test strip with enzyme glucose oxidase detects only glucose? (Correct
Answers) 1) Enzyme has specific shape to active site
OR
1) Active site has specific tertiary structure
2) Only glucose fits/ has complementary structure to form ES complexes
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