2026 HCI 9477 H2 Biology Prelim P4 MS

1 HWA CHONG INSTITUTION (COLLEGE SECTION) 2026 JC2 9477 H2 BIOLOGY PRELIMINARY EXAMINATIONS PAPER 4 MARK SCHEME QUESTION 1 (a)(i) Complete Fig. 1.3 to show how you will prepare your serial dilution. [3] 1 correct concentrations (0.5, 0.25, 0.125, 0.0625) and % at least once 2 shows transfer of 10 cm 3 to each beaker from the previous beaker 3 shows 10 cm 3 of water added to each beaker (ii) State the volume of Benedict’s solution you will use for each reducing sugar test. Explain why you have selected this volume. [1] 2 cm 3 or a volume greater than 2 cm 3 and explains that equal or excess volume needed (iii) Complete Table 1.3 to record your results. [1] results show the correct trend for times of known concentrations, the higher the percentage concentration of glucose the shorter the time to first colour change (iv) Record your results in an appropriate table. [4] 1 correct heading for independent variable 2 correct heading for dependent variable 3 results for each sampling time 4 results recorded to nearest whole second (v) Use your results in (a)(iii) and (a)(iv) to estimate the percentage concentration of glucose in the samples taken at 5 , 10 and 15 minutes. [1] results used correctly to estimate the concentration of glucose in the samples taken at 5, 10 and 15 minutes (vi) Suggest a reason for the difference in percentage concentrations of glucose estimated in (a)(v) . [1] (concentration higher at 15 minutes) glucose had more time to diffuse out of the dialysis tubing into the water (vii) A possible source of error when carrying out step 10 is shown in Table 1.4. Describe another possible source of error when carrying out the Benedict’s test, and complete Table 1.4 by stating the type of errors as systematic or random, and the effects the errors may have on the results. Table 1.4 source of error systematic error or random error effects on the results the line at 1.0 cm 3 on the syringe used in step 10 actually measures a volume of 0.95 cm 3 and not 1.0 cm 3 systematic no effect use of naked eye to judge first colour change is subjective random OR idea of inaccurate judging first colour change systematic no effect [2]

2 (b)(i) Calculate the percentage decrease in concentration of Q between 5 minutes and 20 minutes. Show your working and give your answer to two significant figures. [2] 1 shows (280 – 75) / 280 x 100 2 correct answer to 2 significant figures (ii) Account for the difference in the rates of decrease in the concentration of Q from 0 to 10 minutes and from 10 to 20 minutes. [2] 1 (0 to 10 minutes) ref. to a steep concentration gradient 2 (10 to 20 minutes) ref. to a less steep concentration gradient (c) Draw a bar chart of the data in Table 1.6 on the grid in Fig. 1.5. Use a sharp pencil. [4] 1 x- axis: type of sugar + bars labelled glucose, fructose, sucrose and y- axis: mass of sugar / g per 100 g fruit 2 scale on x -axis: even width of six bars and scale on y -axis: 2 g per 100 g to 2 cm + labelled at least every 2 cm 3 correct plotting of all six bars 4 key / legend indicating type of fruits (apple and pineapple) [Total: 21]

3 QUESTION 2 (a) Use your microscope, with an appropriate objective lens, to search the slide E to find two whole cells that are adjacent to each other. (a) (i) Make a high-power drawing of the two cells that you have selected on slide E in the section labelled Elodea cells in distilled water in Table 2. ) (ii) Make a high-power drawing of the two cells that you have selected on slide E in the section labelled Elodea cells in sodium chloride solution in Table 2. Label the cell surface membrane of one cell with X in your drawing. Table 2 (i) Elodea cells in distilled water (ii) Elodea cells in sodium chloride solution [4] 1 clear continuous lines + cell wall shown as double lines 2 correct size + shape of detailed drawing (at least 50% of space, elongated shape) 3 at least 5 chloroplasts drawn per cell, of correct proportion 4 correct label for cell surface membrane using X in (ii), which has pulled away from cell wall

4 (b) Plan an investigation to compare the salinity tolerance in Elodea canadensis and Elodea nuttallii , by studying the percentage of plasmolysed cells in the leaf tissues over a range of salt concentrations. [10] Variables (1m – all or none) V1 Independent variable – concentration of sodium chloride solution / salt V2 Dependent variable – percentage plasmolysis Method (max 5m) M1 IV Manipulation – Ref to using syringes to prepare 5 different concentrations of sodium chloride solution using 5% sodium chloride solution (stock) and distilled water by simple / serial dilution M2 CV Control (time) – Ref to use stopwatch + soaking leaf samples for same amount of time in the various concentrations of sodium chloride M3 CV Control (volume) - Ref to use of syringe / dropper to soak leaf samples in same volume of the various concentrations of sodium chloride M4 DV Measurement – Ref to mounting of sample on microscope slide + use of cover slip and mounted needle to prepare viewing of leaf samples M5 DV Measurement – Ref to appropriate use of light microscope i.e. use of course adjustment knob + fine adjustment knob to bring specimen into focus M6 CV Control (magnification) – Ref to using same objective (i.e. same magnification) to view samples under light microscope M7 DV Measurement – Ref to counting / recording number of plasmolysed cells and number of non-plasmolysed cells in one field of view M8 CV Control (plant specimen) – Ref to using leaves from same plant specimen Reliability and Control (ma