Fig. 3.1 summarises protein metabolism in the body. Diagram text: 'protein broken down in the stomach by enzyme A'; 'protein broken down in the small intestine by enzyme B'; 'amino acids absorbed into the bloodstream'; 'blood vessel C'; 'surplus amino acids changed into urea in the liver'; 'urea removed from the blood in the kidney and excreted'. Table 3.1 gives the results of an investigation. Group X ate bread, jam, orange juice, lettuce, fruit. Group Y ate nuts, milk, bread, cheese, meat. Early the next morning, urine was tested for urea concentration.
(a(i))[2]
Using Fig. 3.1, state the names of enzyme A and enzyme B.
(a(ii))[1]
Give the name of blood vessel C.
(a(iii))[1]
Name the capillary structure in the kidney that filters urea from the blood.
(b(i))[2]
Calculate the mean concentration of urea for the students in group Y. Give your answer to two significant figures.
(b(ii))[3]
Explain the difference between the mean concentration of urea in the two student groups.
(b(iii))[2]
One student said: 'To make a fair comparison, we should have ensured that the students in each group drank the same volume of water'. Explain why this student is correct.
Worked solution & mark scheme
This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: “pepsin.” …