Explain how urea is produced in the body and describe how the kidneys remove it from the blood.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Urea is a waste product that must be removed from the body to maintain a constant internal environment. This removal is an example of excretion.
Model answer (5 marks)
Urea is produced in the liver by the urea cycle, where excess amino acids are broken down and their nitrogen is converted into urea.
The urea is then transported in the bloodstream to the kidneys.
In the kidneys, urea is filtered out of the blood by the glomerulus.
It then passes into the renal tubules and is excreted unchanged.
Finally, urea leaves the body dissolved in urine, travelling through the bladder and out via the urethra.
The urea is then transported in the bloodstream to the kidneys.
In the kidneys, urea is filtered out of the blood by the glomerulus.
It then passes into the renal tubules and is excreted unchanged.
Finally, urea leaves the body dissolved in urine, travelling through the bladder and out via the urethra.
Examiner tips
- Use the phrase "urea cycle" and mention the liver. Show the transport step. Explain filtration at the glomerulus. Mention excretion via bladder/urethra.
- common_mistakes
- :
- Confusing urea production with the kidneys. Forgetting to mention the glomerulus. Saying urea is reabsorbed instead of excreted.
Mark scheme (5 marks)
- Urea is produced in the liver
- Urea is formed from the breakdown of excess amino acids
- Urea is transported in the blood to the kidneys
- Urea is filtered out of the blood in the kidneys
- Urea leaves the body dissolved in urine (via the bladder / urethra)
Key terms in this question
Related
- All Eduqas A-Level Biology revision notes →
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- Decode the mark scheme abbreviations →
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