Question 1
Which organ excretes carbon dioxide?
- Kidney
- Liver
- Lung
- Bladder
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Answer: C (lung) (1)
Question 2
The kidneys are part of the urinary system. (a) State two substances, other than urea, that are excreted by the kidneys. [1] (b) Name the part of the urinary system that (i) stores urine, [1] (ii) carries urine out of the body. [1] (c) Name the tube that carries urine from each kidney to the bladder. [1]
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- (a) excess water and excess ions (1) allow salts; both needed for the mark
- (b)(i) bladder (1)
- (b)(ii) urethra (1) reject ureter
- (c) ureter (1) reject urethra
Question 3
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanA kidney is cut open lengthways. Which option names the outer region and the inner region of the kidney?
- Outer: cortex; inner: medulla
- Outer: medulla; inner: cortex
- Outer: cortex; inner: ureter
- Outer: medulla; inner: ureter
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Answer: A (cortex outside, medulla inside) (1)
Question 4
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanOutline how the nephron and its blood vessels form urine from blood.
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- blood is filtered in the glomerulus (1)
- water, glucose, urea and ions pass out of the blood / into the nephron (1) allow Bowman's capsule
- all of the glucose is reabsorbed (into the blood) (1)
- most of the water and some of the ions are reabsorbed (into the blood) (1)
- urine contains urea, excess water and excess ions (1)
- Max 4
Question 5
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanThe table shows the concentration of three substances in the blood plasma, in the fluid filtered into the nephron and in urine from a healthy person. (a) Calculate how many times greater the concentration of urea is in urine than in blood plasma. Give your answer to the nearest whole number. [2] (b) Explain why there is no glucose in the urine. [1] (c) Explain why there is no protein in the filtered fluid. [1]
| Substance | Blood plasma | Filtered fluid in nephron | Urine |
|---|---|---|---|
| Glucose | 0.10 | 0.10 | 0.00 |
| Protein | 7.00 | 0.00 | 0.00 |
| Urea | 0.03 | 0.03 | 2.00 |
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- (a) 2.00 ÷ 0.03 (1)
- (a) = 67 (times) (1) the second mark needs the answer to the nearest whole number; 66.7 scores the first mark only
- (b) all the glucose is reabsorbed (back into the blood) (1)
- (c) protein molecules are too large (to be filtered) / cannot pass out of the glomerulus (1)
Question 6
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanThe liver has two roles in the use of amino acids. (a) Describe the role of the liver in the assimilation of amino acids. [1] (b) Define deamination. [2] (c) State the organ in which urea is formed. [1]
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- (a) the liver converts amino acids to proteins (1)
- (b) removal of the nitrogen-containing part of amino acids (1) allow removal of the amino group
- (b) to form urea (1)
- (c) liver (1)
Question 7
Supplement (what this means)
Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels meanUrea is made in the liver and removed from the body by the kidneys. (a) Explain why it is important that urea is excreted. [2] (b) State where urea comes from. [1]
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- (a) urea is toxic / poisonous (1)
- (a) so it would build up (in the blood / body) and cause harm (1) ignore urea is a waste
- (b) excess amino acids (1) allow the breakdown / deamination of amino acids