Science — AI-generated practice question

Structure of a Nephron:
Each nephron consists of a cup-shaped Bowman's capsule that surrounds a cluster of thin-walled blood capillaries (glomerulus). The capsule leads into a long coiled tubule.

Functioning / Urine Formation:
Blood is filtered under pressure in the glomerulus. The filtrate (containing water, glucose, amino acids, urea, salts) collects in the Bowman's capsule. As this filtrate passes through the tubule, useful substances like glucose, amino acids, salts and a large amount of water are selectively reabsorbed back into the blood. The remaining concentrated waste fluid is urine.

Regulation of Urine Amount:
The amount of water reabsorbed depends on:

• How much excess water is present in the body.
• How much dissolved waste needs to be excreted.

The initial filtrate formed daily is ~180 L, but only 1–2 litres is excreted as urine due to reabsorption in the tubules.

Source: Chapter 5, Section 5.5.1

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• Examiners expect you to name Bowman's capsule, glomerulus (capillary cluster), and tubule for structure marks.
• For functioning, the key terms are filtration and selective reabsorption — both must appear.
• For regulation, always link the two factors: excess water in body + amount of dissolved waste. The 180 L vs 1–2 L figure is a scoring detail worth including.
• Do not write about the ureter/bladder in detail — that's the excretory system, not the nephron.