IMO Practice Test — Excretory Products and Their Elimination
6 Questions • 15 min • Olympiad level
15:00
Question 1 of 6
Blood cells and large proteins are normally absent from the glomerular filtrate because they:
Are too big to pass through the filter
Are destroyed in the kidney
Turn into urea
Are reabsorbed first
Explanation: Filtration holds back large components; only water and small molecules pass into the tubule.
Question 2 of 6
Glucose in the urine of a person may indicate diabetes because the filtered glucose:
Exceeds what the tubules can reabsorb
Is made by the kidney
Cannot be filtered
Turns into urea
Explanation: If blood glucose is very high, the tubules cannot reabsorb it all, so some appears in urine.
Question 3 of 6
On a hot day with heavy sweating, the urine produced tends to be:
Small in amount and concentrated
Large in amount and dilute
Unchanged
Full of glucose
Explanation: Water lost in sweat triggers ADH, so the kidney conserves water and makes little, concentrated urine.
Question 4 of 6
Reabsorption is essential because without it the body would:
Lose vital water, glucose and salts in the urine
Make no urea
Stop breathing
Gain weight
Explanation: Reabsorption recovers the useful substances from the 180 L of filtrate, preventing their loss.
Question 5 of 6
In haemodialysis, urea moves from the blood into the dialysing fluid by:
Diffusion across a selectively permeable membrane
Active pumping by the machine
Boiling
Filtration of cells
Explanation: Urea diffuses down its concentration gradient across the membrane into the waste-free dialysing fluid.
Question 6 of 6
Drinking plenty of water helps prevent kidney stones because it:
Dilutes the salts so they are less likely to crystallise
Stops filtration
Adds urea
Removes nephrons
Explanation: More water keeps salts dissolved and flushed out, reducing the chance of crystals forming.