How is carbon dioxide transported to the lungs?
It is carried in the blood.
Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) · 13.1
Revise Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) specification point 13.1, Excretion in humans, with free active-recall flashcards. Flip through the set or review every question and answer below.
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How is carbon dioxide transported to the lungs?
It is carried in the blood.
How does carbon dioxide leave the body after reaching the lungs?
It passes from the blood into the air in the lungs, then leaves when that air is breathed out.
Why is removing carbon dioxide through the lungs classed as excretion?
Because it removes a waste product from the body.
What three substances do the kidneys remove from the blood to produce urine?
Urea, excess water and excess ions.
What route does urine follow from the kidneys to outside the body?
Kidneys → ureters → bladder → urethra → outside the body.
What is the bladder’s role in urinary excretion?
It stores urine before it leaves the body.
How are the cortex and medulla arranged in the kidney?
The cortex is the outer region; the medulla is the inner region.
What is a nephron?
A filtering unit associated with blood vessels.
Where in the kidney is the glomerulus located?
In the cortex.
Which four substances does the glomerulus filter from the blood into the nephron?
What happens to glucose as filtered fluid passes along the nephron?
All of the glucose is reabsorbed into the blood through associated vessels.
What happens to ions as filtered fluid passes along the nephron?
Some of the ions are reabsorbed into the blood through associated vessels.
What happens to water as filtered fluid passes along the nephron?
Most of the water is reabsorbed into the blood through associated vessels.
What does the fluid remaining in the nephron after reabsorption form?
Urine.
What three substances does urine contain?
How does the liver assimilate absorbed amino acids?
It joins amino acids to make proteins used by the body.
How are absorbed amino acids transported to the liver?
They are carried in the blood.
What happens to excess amino acids during deamination?
Their nitrogen-containing part is removed, and urea is formed.
Where in the body does deamination of excess amino acids occur?
In the liver.
Why is excretion of urea important?
Urea is toxic if it accumulates, so it must be removed from the body.