Free Excretion questions for IGCSE Biology (0610), part of Disease, gas exchange & respiration. Each question has the answer and the marking points an examiner would look for.
Generate a full Excretion worksheet →All Disease, gas exchange & respiration questionsThe kidneys and liver are involved in excretion.
1 Proteins are filtered into the kidney tubule in large amounts.
2 Carbon dioxide is an excretory product of respiration.
3 Urea is made in the kidneys.
Which statements are correct?
Answer: D
The kidneys filter the blood and produce urine.
Name two substances found in urine.
Explain why glucose is not normally found in urine.
Explain how urea is formed.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | urea; water; salts Any 2 of: urea; water; excess salts (ions) B2 | 2 |
| (b) | reabsorbed in nephron glucose is filtered but then all reabsorbed back into the blood (in the nephron tubule) B2 | 2 |
| (c) | deamination of excess amino acids in liver excess amino acids are deaminated in the liver B1 the nitrogen-containing part forms urea B1 | 2 |
The kidneys are organs of the excretory system.
Define the term excretion.
State the name of the waste substance excreted by the lungs.
State the names of the structures that carry urine from each kidney to the bladder, and from the bladder out of the body.
Table 3.1 shows the concentration of three substances in the blood plasma entering a kidney, in the fluid in the Bowman’s capsule, and in the urine.
| substance | concentration in plasma / g per dm³ | concentration in Bowman’s capsule / g per dm³ | concentration in urine / g per dm³ |
|---|---|---|---|
| protein | 80 | 0 | 0 |
| glucose | 1.0 | 1.0 | 0 |
| urea | 0.3 | 0.3 | 20 |
Describe and explain the differences in the concentrations of the three substances in Table 3.1.
The liver is also involved in excretion. Describe how excess amino acids are processed in the liver.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | removal of waste products of metabolism; toxic materials and substances in excess removal of the waste products of metabolism and toxic materials B1 and substances in excess of requirements B1 | 2 |
| (b) | carbon dioxide carbon dioxide B1 | 1 |
| (c) | ureter; urethra ureter B1 urethra B1 | 2 |
| (d) | protein too large to be filtered; glucose filtered then all reabsorbed; urea filtered, water reabsorbed so concentrated protein absent from the filtrate B1 protein molecules are too large to pass through the glomerulus into the capsule B1 glucose is filtered (same concentration in capsule as plasma) B1 all glucose is reabsorbed (in the tubule) so none in urine B1 urea is filtered and not reabsorbed B1 urea is more concentrated in urine because (most) water is reabsorbed B1 | 6 |
| (e) | deamination; nitrogen-containing part removed and converted to urea deamination B1 the nitrogen-containing part is removed and converted into urea B1 | 2 |
The human excretory system includes the kidneys, ureters, bladder and urethra.
State the function of the ureter and the bladder.
Name two excretory products and the organs that excrete them.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | carries urine; stores urine ureter carries urine from kidney to bladder B1 bladder stores urine B1 | 2 |
| (b) | CO₂ lungs; urea kidneys carbon dioxide by the lungs B1 urea by the kidneys B1 | 2 |
The liver plays a role in excretion.
Name the product formed when excess amino acids are deaminated.
Explain why the body cannot store excess amino acids.
State one other function of the liver.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | urea urea B1 | 1 |
| (b) | no storage; toxic amino acids cannot be stored in the body B1 | 1 |
| (c) | breaks down alcohol/drugs; glycogen storage; bile Any 1 of: breakdown of alcohol/drugs; converting glucose to glycogen; making bile B1 | 1 |
This question is about excretion.
Define excretion.
Describe how urea is formed in the liver.
Describe how urine is formed in a nephron.
Explain why a healthy person’s urine contains no glucose.
A person drinks a large volume of water. Describe how the volume and concentration of their urine change.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | removal of waste products of metabolism and substances in excess removal of the waste products of metabolism B1 and substances in excess of requirements B1 | 2 |
| (b) | excess amino acids deaminated; nitrogen-containing part removed; converted to urea excess amino acids are deaminated B1 the nitrogen-containing (amino) group is removed B1 and converted into urea B1 | 3 |
| (c) | filtration under pressure in glomerulus; glucose, water, salts, urea filtered; selective reabsorption of glucose and some salts; water reabsorbed Any 4 of: blood is filtered under high pressure in the glomerulus; water, glucose, salts and urea enter the nephron; all the glucose is reabsorbed; some water and salts are reabsorbed as required; the remaining fluid is urine B4 | 4 |
| (d) | all glucose reabsorbed back into blood in the nephron glucose is filtered in the glomerulus B1 but all of it is reabsorbed into the blood B1 | 2 |
| (e) | larger volume; more dilute larger volume of urine B1 more dilute (lower concentration) B1 | 2 |
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