1. Carbon dioxide is excreted by the
- skin only
- kidneys
- liver
- lungs
Answer: D) lungs
Explanation: Expired air removes CO₂. O Level Biology · Topic 13 Excretion · 13.1 Excretion
MCQs / Biology / O Level Biology: Excretion
O Level Biology: Excretion MCQs — Biology
15 multiple-choice questions on O Level Biology: Excretion from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.
2. Which tube carries urine from the kidney to the bladder?
- Urethra
- Ureter
- Collecting duct
- Renal vein
Answer: B) Ureter
Explanation: The ureter links kidney and bladder. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
3. In the glomerulus, which substance is NOT normally filtered into the Bowman's capsule?
- Glucose
- Red blood cells
- Urea
- Water
Answer: B) Red blood cells
Explanation: Cells and proteins are too large to filter. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
4. Which substance is completely reabsorbed in a healthy nephron?
- Glucose
- Salts
- Urea
- Water
Answer: A) Glucose
Explanation: All glucose returns to the blood. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
5. Removing faeces from the body is called
- deamination
- excretion
- egestion
- filtration
Answer: C) egestion
Explanation: Faeces are not metabolic waste. O Level Biology · Topic 13 Excretion · 13.1 Excretion
6. Urine normally contains
- urea, excess water and excess ions
- glucose and protein
- amino acids
- red blood cells
Answer: A) urea, excess water and excess ions
Explanation: Wastes and excesses form urine. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
7. Excretion is the removal of
- all water from the body
- undigested food
- toxic materials and waste products of metabolism
- food from the mouth
Answer: C) toxic materials and waste products of metabolism
Explanation: Definition of excretion. O Level Biology · Topic 13 Excretion · 13.1 Excretion
8. Why must urea be excreted?
- It is a source of energy
- It forms proteins
- It is needed in the blood
- It is toxic
Answer: D) It is toxic
Explanation: Urea build-up damages cells. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
9. What is the correct order of parts of a nephron?
- Bowman's capsule → tubule (loop of Henle) → collecting duct
- collecting duct → loop of Henle → Bowman's capsule
- glomerulus → ureter → tubule
- loop of Henle → Bowman's capsule → urethra
Answer: A) Bowman's capsule → tubule (loop of Henle) → collecting duct
Explanation: Filtrate passes from capsule through the tubule to the collecting duct. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
10. Urea is made in the
- liver
- lungs
- kidneys
- bladder
Answer: A) liver
Explanation: The liver makes urea from excess amino acids. O Level Biology · Topic 13 Excretion · 13.1 Excretion
11. Urine is stored in the
- kidney
- ureter
- urethra
- bladder
Answer: D) bladder
Explanation: The bladder stores urine. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
12. Filtration in the glomerulus happens because
- the blood is at low pressure
- of osmosis only
- the blood is at high pressure
- of active transport
Answer: C) the blood is at high pressure
Explanation: Pressure forces small molecules out. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
13. The liver converts amino acids into
- urea and glycogen only
- proteins (assimilation)
- fats only
- glucose only
Answer: B) proteins (assimilation)
Explanation: Assimilation builds proteins such as plasma proteins. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
14. Deamination is
- filtration of blood
- making proteins from amino acids
- absorption of amino acids
- removal of the nitrogen-containing part of amino acids to form urea
Answer: D) removal of the nitrogen-containing part of amino acids to form urea
Explanation: Deamination happens in the liver. O Level Biology · Topic 13 Excretion · 13.2 Urinary system
15. Urea is made from
- fatty acids
- carbon dioxide
- excess glucose
- excess amino acids
Answer: D) excess amino acids
Explanation: Deamination of amino acids forms urea. O Level Biology · Topic 13 Excretion · 13.1 Excretion
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