OCR GCSE Biology A: Practical skills II: photosynthesis, physiology, microbiology and transport in cells (PAG 5-8) (J247) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover Practical Activity Groups 5 to 8 of Topic B7 (Practical skills) in the OCR GCSE (9-1) Biology A Gateway Science specification (J247), Version 4.0, for first assessment in 2018. Nothing here is Higher Tier only. Revise first with the study guide and the revision notes. The course page is OCR GCSE Biology and the printable list is the OCR GCSE Biology checklist.

Questions

1. A student investigates how the distance of a lamp from a piece of Cabomba affects the rate of photosynthesis, by counting bubbles. (a) State the independent variable and the dependent variable. [2] (b) Give two variables that must be controlled. [2]

2. At a lamp distance of 15 cm, a piece of Cabomba gives off 40 bubbles per minute. Light intensity is inversely proportional to the distance squared. Assume the bubble rate is proportional to light intensity. (a) Predict the rate at 30 cm. [2] (b) Predict the rate at 45 cm, to 2 significant figures. [2]

3. A gas syringe collects oxygen from pondweed at different temperatures for 12 minutes. At 25 °C it collects 3.6 cm³. The rates at other temperatures are 0.12 cm³ per minute at 15 °C, 0.52 cm³ per minute at 35 °C and 0.08 cm³ per minute at 45 °C. (a) Calculate the rate at 25 °C. [2] (b) Calculate the percentage increase in rate from 25 °C to 35 °C. [2] (c) Explain the low rate at 45 °C. [2]

4. Five students measure their pulse at rest and straight after two minutes of stepping. Resting (beats per minute): 68, 75, 71, 66, 70. After exercise: 118, 127, 121, 112, 122. (a) Calculate the mean resting rate and the mean rate after exercise. [2] (b) Calculate the percentage increase in the mean. [2] (c) Explain why pulse rate rises during exercise. [2]

5. A class will use human volunteers to measure ventilation rate before and after exercise. Describe four precautions that make the investigation safe and ethical. [4]

6. A technician prepares dishes for a bacterial lawn. (a) Describe how an inoculating loop is sterilised before it is used. [2] (b) Explain two ways of reducing contamination while the dish is open. [2] (c) Explain why the dishes are incubated at about 25 °C, not 37 °C. [1]

7. Three antibacterial discs, each 6 mm across, are placed on a lawn. The clear zones (including the disc) have diameters: P 21 mm, Q 15 mm, R 9 mm. (a) Calculate the area of the clear zone for P and for Q, in mm² to 3 significant figures. [2] (b) State how many times larger the area for P is than for Q, to 2 significant figures. [1] (c) Give a conclusion and one extra control disc needed for the experiment to be valid. [2]

8. A student seals the lid of a dish fully with tape, incubates it upright at 37 °C, and measures each clear zone in one direction only. (a) Identify two safety faults. [2] (b) Suggest two improvements to the way the zones are measured and recorded. [2]

9. Potato chips are placed in sucrose solutions. Chip masses before and after: 0.1 M, 3.20 g to 3.38 g; 0.3 M, 3.18 g to 3.08 g; 0.5 M, 3.22 g to 2.93 g. (a) Calculate the percentage change in mass at 0.1 M and at 0.5 M, to 1 decimal place. [2] (b) Explain the change at 0.1 M. [2] (c) Predict and explain what happens to the length of the chip at 0.5 M. [2]

10. Technicians need 80 cm³ of 0.6 M sucrose solution from a 1.0 M stock. The percentage changes in a chip experiment were +5.6 at 0.1 M and -3.1 at 0.3 M. (a) Calculate the volumes of stock and water. [2] (b) Estimate the concentration giving no mass change, assuming a straight line between the two points. [3] (c) State what this concentration tells you about the chip. [1]

11. A student draws a bacterial cell 21 micrometres wide, and the drawing is 63 mm wide. (a) Calculate the magnification. [2] (b) State two rules for a good scientific drawing. [2]

12. Plan an investigation into the effect of temperature on the rate of photosynthesis in Cabomba. Include the apparatus and method, how the temperature is controlled, the measurement, and how the results are processed and how the plant is treated. [8]

Answers

1. (a) Independent: distance of lamp from Cabomba [1]; dependent: number of bubbles per minute [1] [2] (b) Any two: temperature (water bath or heat shield) [1]; carbon dioxide or hydrogencarbonate concentration, plant piece or length, or counting time [1] [2] Examiner insight: name the quantity and its unit or time basis; “bubbles” alone is less secure than “bubbles per minute”.

2. (a) Intensity = (15/30)² = 1/4 [1]; rate = 40 x 1/4 = 10 per minute [1] [2] (b) Intensity = (15/45)² = 1/9 [1]; rate = 40/9 = 4.4 per minute [1] [2] Examiner insight: squaring the distance ratio, not just halving or dividing by three, is the usual step to show clearly.

3. (a) 3.6 / 12 [1] = 0.30 cm³ per minute [1] [2] (b) (0.52 - 0.30) / 0.30 x 100 [1] = 73% (73.3) [1] [2] (c) Enzymes of photosynthesis are denatured at high temperature [1], so the active sites no longer fit the substrates and fewer reactions occur [1] [2] Examiner insight: percentage change divides by the original value, not the new one, and linking heat to enzyme shape is a stronger answer than “too hot”.

4. (a) Rest: 350 / 5 = 70 [1]; exercise: 600 / 5 = 120 [1] [2] (b) (120 - 70) / 70 x 100 [1] = 71% (71.4) [1] [2] (c) Muscles respire faster and need more oxygen and glucose [1]; the heart beats faster to deliver them and remove carbon dioxide [1] [2] Examiner insight: give units (beats per minute) and link rate to supply of oxygen and glucose, not only “more energy”.

5. Any four sensible precautions, for example: volunteers give informed agreement and can stop at any time [1]; exclude anyone with a medical condition affected by exercise [1]; keep exercise moderate and the same for all [1]; stop anyone who feels dizzy or unwell [1] [4] Examiner insight: each precaution should be separate and specific; “be careful” earns no credit.

6. (a) Hold the loop in a Bunsen flame until it glows red [1]; let it cool before touching the culture [1] [2] (b) Work close to a Bunsen flame so rising air carries contaminants away [1]; lift the lid only slightly and briefly [1] [2] (c) Harmful human pathogens grow best near body temperature, so a lower temperature makes them less likely to grow [1] [1] Examiner insight: say why each step helps, for example what is carried away or kept out.

7. (a) P: r = 10.5 mm, π x 10.5² = 346 mm² [1]; Q: r = 7.5 mm, π x 7.5² = 177 mm² [1] [2] (b) 346 / 177 = 2.0 times (1.96) [1] [1] (c) P is the most effective at stopping growth (largest zone) [1]; a disc with sterile water (negative control), or repeat plates, is needed [1] [2] Examiner insight: use the radius in πr², and do not claim the bacteria were killed from a clear zone alone.

8. (a) Sealed all round (anaerobic pathogens could grow) [1]; 37 °C favours human pathogens [1] [2] (b) Measure two diameters at right angles and take the mean [1]; repeat on several plates and average [1] [2] Examiner insight: state the hazard and what makes it a hazard, not only the better method.

9. (a) 0.1 M: (3.38 - 3.20) / 3.20 x 100 = +5.6% [1]; 0.5 M: (2.93 - 3.22) / 3.22 x 100 = -9.0% [1] [2] (b) The solution has a higher water potential than the chip cells [1], so water moves in by osmosis through the partially permeable membrane [1] [2] (c) The length decreases [1]; water leaves the cells by osmosis and the tissue shrinks [1] [2] Examiner insight: name the direction of water movement and the membrane; never say solute moves through the membrane.

10. (a) Stock = 0.6 x 80 = 48 cm³ [1]; water = 80 - 48 = 32 cm³ [1] [2] (b) Total span 5.6 + 3.1 = 8.7 [1]; fraction 5.6 / 8.7 of the 0.2 M gap [1]; 0.1 + 0.2 x 0.644 = 0.23 M [1] [3] (c) The chip and solution have about the same water potential, so no net water movement [1] [1] Examiner insight: show the interpolation or read the graph crossing carefully; working shown clearly makes the answer easy to follow.

11. (a) 63 mm = 63 000 micrometres [1]; 63 000 / 21 = x3000 [1] [2] (b) Any two: sharp single lines, no shading [1]; proportions correct; label lines ruled and not crossing [1] [2] Examiner insight: convert both lengths to one unit before dividing.

12. Any eight: cut Cabomba under water, same length, upside down in a tube [1]; hydrogencarbonate added for carbon dioxide [1]; tube in a water bath at set temperatures, such as 10 to 40 °C, checked with a thermometer [1]; fixed lamp distance and a heat shield, then wait two minutes to adjust [1]; count bubbles for a fixed time or collect gas in a syringe [1]; repeat three times at each temperature and take the mean [1]; calculate rate per minute and plot a graph with temperature on the horizontal axis [1]; handle the plant gently and keep mains equipment away from water [1] [8] Examiner insight: organise the answer as apparatus, variable changed, variables controlled, measurement, repeats, processing, so each point is easy to find.

Where marks are usually lost

• Writing a rate with no time unit.
• Using the diameter as the radius in πr².
• Calculating percentage change from the new value instead of the original.
• Forgetting to convert micrometres to millimetres before finding magnification.
• Saying “light” or “heat” instead of naming the controlled variable.
• Describing water potential as a movement of solute instead of water.
• Answering “to stop contamination” without saying how a step does this.
• Giving vague ethical points such as “be careful”.
• Treating a clear zone as proof that every bacterium died.

Next steps

• Review the revision notes and the study guide.
• Visit the OCR GCSE Biology course page and tick off the checklist.
• Try all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

OCR GCSE (9-1) Biology A (Gateway Science) specification J247, Version 4.0, for first assessment in 2018, published by OCR: Topic B7 Practical skills, Practical Activity Groups 5 to 8.