2023 RI Prelim H2 Biology P4 Answers

H2 Biology ● RI Prelim 2023 PAPER 4 (a) You will need to carry out a serial dilution of the 10.00% protein solution, P, to reduce the concentration by half between each successive dilution. You will need to prepare four concentrations of protein solution in addition to the 10.00% protein solution, P. After the serial dilution is completed, you will need to have 5 cm3 of each concentration available for use. (i) In the space below, draw a table to show how you will prepare the serial dilution. [3] Final concentration of protein solution/% Concentration of protein solution used/% Volume of protein solution used/cm3 Volume of W/water used/cm3 10.00 10.00 10.0 0.0 5.00 10.00 5.0 5.0 2.50 5.00 5.0 5.0 1.25 2.50 5.0 5.0 0.63 1.25 5.0 5.0 1. C – Headings and units with correct final concentration of protein solution and concentration of protein solution used; 2. V - correct volumes of protein solution and water (W) used; 3. P - concentration recorded to 2 dp and volume recorded to 1 dp ; (ii) Record your results in an appropriate table. You may use the same symbols for more than one test-tube. [2] protein concentration/% symbol 10.00 +++++ 5.00 ++++ 2.50 +++ 1.25 ++ 0.63 + 0.00 - 1. H - correct heading with units for independent variable (protein concentration/%) correct heading for dependent variable (symbol); A: colour intensity, colour after 1 min, etc (instead of symbol) in heading

R: concentration of P in heading 2. P - records readings for all concentrations with symbols with decreasing trend; (iii) Fig. 1.1 shows a scale of protein concentrations used in this investigation. The position for 0.00% and 10.00% are shown on the scale. Complete the scale in Fig. 1.1 by showing the positions of the protein concentrations you prepared in step 1. [1] 0.00% 10.00% correct positions of protein concentrations; (iv) Use your results in (a)(ii) and (a)(iii) to estimate the protein concentration of U, X and U+X. Show your estimates on Fig. 1.1 by drawing labeled arrows (↓) at the correct positions on the scale. [2] 1. U correctly labeled at 1.25%<U<2.5% A: U=1.25 or U=2.5 R: if U is greater than 2.5 2. Both X and U+X labeled at 0%<X<0.63% and 0%<U+X<0.63% R: if X or U+X is pointing to 0 (v) Using your result in (a)(iv), estimate the concentration of protein in U over a period of 24 hours and state the possible medical condition of the patient indicated by U. Show your working in the space provided. [2] 1. Correct calculation 10.00% ➔ 1000mg 2.00% ➔ 1000/10 X 2 = 200 mg (A: range of values between 125 to 250mg) (ECF: if U in a(iv) is incorrect) 2. Correct medical condition - Urinary tract infection or kidney tubular disease (vi) Solution X was extracted from the human gastrointestinal tract. Suggest t