1
1 mark
1 markWhich statement correctly describes urea?
It is formed from deamination of excess carbohydrates
It contains nitrogen
It is more soluble than ammonia
It is excreted by the liver
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Excretion (OCR A Level Biology)
Exam Questions
3 hours34 questions21 mark
1 markThe diagram below shows a kidney nephron.
Which row in the table correctly identifies structures X and Y and the location at which ultrafiltration takes place?
| Structure X | Structure Y | Location of ultrafiltration | |
| A | Bowman’s capsule | Proximal convoluted tubule | Structure X |
| B | Glomerulus | Proximal convoluted tubule | Structure Y |
| C | Bowman’s capsule | Loop of Henle | Structure X |
| D | Glomerulus | Distal convoluted tubule | Structure Y |
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31 mark
1 markWhich of the following statement(s) correctly explain(s) a feature of an efficient selective reabsorption surface?
| 1 | The surface is one cell thick to reduce diffusion distance |
| 2 | Microvilli increase the surface area for diffusion |
| 3 | Cells contain many mitochondria to release energy for sodium-potassium pumps |
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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41 mark
1 markThe diagram below shows a photomicrograph of a section of the human liver.
Structure P is lined with endothelial cells that allow the blood to come into contact with the cells of the liver tissue.
Which of the following identifies structure P ?
Central vein
Hepatocyte
Sinusoid
Hepatic portal vein
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51 mark
1 markWhich of the following correctly describes (a) problem(s) that would occur as a result of kidney failure?
| 1 | Glomerular filtration rate (GFR) decreases |
| 2 | Ion balance is not maintained |
| 3 | Risk of arrhythmia and cardiac arrest |
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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11 mark
1 markDamage to the hypothalamus results in lower water potential of the blood.
Which of the following, A to D, explains these observations?
ADH release increases the water potential of blood.
Mineralocorticoids affect cells in the loop of Henle.
Fewer water channels are inserted into the cell surface membranes of the collecting duct.
The anterior pituitary releases hormones into the blood.
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21 mark
1 markThe hormone aldosterone is produced by the adrenal cortex. Excess production of aldosterone can result in high blood pressure.
The following statements describe processes that occur as a result of aldosterone secretion:
- Na+/K+ pumps in the collecting duct of the kidney move three Na+ ions into the blood and two K+ ions out of the blood.
- Cl− ions enter the blood to maintain electrochemical balance.
- H+ ions enter cells lining the kidney tubules.
Which of the above statements explain(s) why excess aldosterone production can result in high blood pressure?
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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31 mark
1 markOne treatment for thyroid cancer is radioactive iodine. The radioisotope I131 is used.
The thyroid gland absorbs any iodine that enters the body, so the radioactive isotope kills the cancerous cells in the thyroid gland. The I131 is then excreted from the body.
Different body fluids excrete different proportions of I131, as shown in the following graph.
Which of the following, A to D, correctly explains the different proportions of I131 in each body fluid?
I131 is very soluble in water.
I131 is able to cross capillary walls.
The kidneys are more efficient at excreting I131 than the lungs.
The thyroid gland is well supplied with blood.
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41 mark
1 markThe hormone hCG can be detected in urine using pregnancy tests.
Which of the following properties of the hormone hCG allows it to be detected in urine?
hCG is a polar molecule.
hCG has a molecular mass of less than 69,000.
hCG is a polypeptide.
hCG binds to cells using glycoproteins.
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51 mark
1 markThe image below shows the structure of the nucleotide base guanine.
Bird droppings are known as guano because they contain a high proportion of guanine. Unlike mammals, birds excrete nitrogenous waste as guanine instead of urea. Guanine is synthesised from ammonia in the liver.
The following statements relate to guanine:
- Ammonia is more toxic than guanine.
- Urea is more soluble in water than guanine.
- Guanine has a high proportion of nitrogen.
Which of the statements correctly explains why birds excrete guanine?
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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61 mark
1 markThe kidneys of a healthy individual filter 178 dm3 day-1 of fluid from the glomeruli into the renal capsules. However, only 1.5 dm3 day-1 of urine is produced.
What percentage of the filtrate is reabsorbed back into the blood?
176.5
0.8
11.8
99.2
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71 mark
1 markWhich of the following statements correctly describes the function of the liver?
The formation of urea by combining amino groups and hydrogen atoms removed from excess amino acids.
Excretion of urea
Conversion of ethanol into ethanal by alcohol dehydrogenase
Conversion of ammonia to urea during the Krebs cycle.
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81 mark
1 markThe microscope images below are taken from four different tissue types.
Which image, from A-D, shows liver tissue?
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91 mark
1 markWhich of the following statements describe features that aid the process of ultrafiltration?
- The glomerulus has an afferent arteriole and an efferent arteriole.
- The blood in the afferent arteriole has a different composition to the blood in the efferent arteriole.
- The basement membrane prevents the passage of large proteins out of the glomerulus.
- The afferent arteriole is wider than the efferent arteriole.
Only 1 and 2
Only 2 and 3
Only 3
Only 3 and 4
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11 mark
1 markThe image below shows a micrograph of liver tissue.
Which of the following statements, A to D, correctly describes events occurring at the location marked X ?
Blood being transported from the intestines to the liver cells
Amination of protein to form urea
The storage of glucose that has been converted from glycogen in response to insulin
Breakdown of toxic hydrogen peroxide
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21 mark
1 markGraphs A to D represent the percentage concentration of water and sodium chloride ions in the filtrate flowing through regions of the loop of Henle.
Which graph, A to D, shows the correct percentage concentrations of water and sodium chloride ions along the loop of Henle?
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31 mark
1 markWhich of the rows, A to D, correctly identifies the effect of eating salty food on the osmoreceptors, antidiuretic hormone (ADH) and urine production?
| Osmoreceptor in the hypothalamus | Effect of ADH | Urine production | |
| A | Gain water from the blood | Removal of water channels from kidney cell membranes | A large volume of less concentrated urine |
| B | Lose water into the blood | Binds to receptors on membranes of kidney cells | A large volume of less concentrated urine |
| C | Lose water into the blood | Insertion of water channels into kidney cell membranes | A small volume of more concentrated urine |
| D | Gain water from the blood | Binds to receptors on membranes of kidney cells | A small volume of more concentrated urine |
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41 mark
1 markThe table below shows the concentration of electrolytes in blood plasma and in a urine sample from a patient.
Note that the ‘reference range in plasma’ is a range of normal values for blood plasma concentration.
| Blood plasma | Urine | Reference range in plasma | |
| Sodium ions / mmol L-1 | 150 | 120 | 136 - 144 |
| Potassium ions / mmol L-1 | 5 | 100 | 3.7 - 5.1 |
| Chloride ions / mmol L-1 | 120 | 118 | 97 - 105 |
| Calcium / mg dL-1 | 9.8 | 2.3 | 8.5 - 10.2 |
Which of the following statements, A to D, is likely to be true for the patient?
The patient has a low GFR due to the lower concentrations of ions in the urine
The patient is undergoing dialysis and the blood plasma and urine sample have been taken after the treatment
The patient has high blood pressure due to an increased blood volume
There is damage in the basement membrane between the glomerulus and Bowman’s capsule of the patient’s kidneys
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51 mark
1 markWhich of the following statements, A to D, explains why urine can be used in pregnancy testing?
Urine samples can be tested using gas chromatography and mass spectrometry
The pregnancy hormone hCG is a protein, so is not filtered by the kidneys.
Monoclonal antibodies can only bind to hCG in the urine.
Traces of the embryo’s excretory products can be found in the mother’s urine.
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