al cells do not contain chloroplasts.","markscheme":"- States that onion bulb cells are underground, so they do not receive light / are in the dark B1\n- States that the function of chloroplasts is to absorb light (energy) for photosynthesis B1\n- Concludes that without light, these cells cannot photosynthesise (making chloroplasts redundant / a waste of resources) B1","marks":3,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"link_light_to_function","label":"Link light to function","steps":[{"type":"text","order":0,"title":"Identify the light condition","content":"The onion bulb grows underground, so its epidermal cells are in the dark and do not receive light. **This earns the first B1 mark.**","highlights":[{"text":"Onion bulbs grow underground.","location":"specification"}]},{"type":"text","order":1,"title":"Explain chloroplast function","content":"Chloroplasts absorb light energy for photosynthesis. **This earns the second B1 mark.**"},{"type":"text","order":2,"title":"State the conclusion","content":"Because there is no light to absorb, these epidermal cells cannot photosynthesise. Chloroplasts would therefore be redundant — they would be a waste of the cell's resources. **Making this link earns the final B1 mark.**"}]}],"generatedAt":"2026-07-22T07:41:58.167Z","modelVersion":"gpt-5.6-terra+diagrams-1","explanationVersion":"v3"},"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"3b09f1a7-1846-457e-aeb5-b6dc20adfa00","revisionId":"4044ad6b-a2f9-47d5-9b5f-767511934d81","questionNumber":null,"questionType":"LA","specification":"A student has prepared a slide of stained *Allium* epidermal cells to examine cell walls and nuclei.","difficulty":4,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"b16a545d-a4ff-45a3-8f78-b643b2048f69","label":null,"content":"Detail the step-by-step procedure the student must follow to safely position, locate, and focus on these plant cells under high power magnification, starting with the slide placed on the stage.","markscheme":"- Secure the slide onto the stage and select the lowest power objective lens by rotating the nosepiece B1\n- Adjust the stage upwards using the coarse focus knob while looking from the side to avoid crushing the slide, then look through the eyepiece and lower the stage until the specimen comes into focus M1\n- Rotate to the high-power objective lens and turn only the fine adjustment knob until the cell structures (walls and nuclei) are in sharp, clear focus A1","marks":3,"order":0,"markingRubric":null,"explanation":{"methods":[{"id":"safe_focusing","label":"Safe microscope focusing","steps":[{"type":"text","order":0,"title":"Secure and start low","content":"Put the slide under the stage clips so it cannot move. Then rotate the nosepiece to select the **lowest-power objective lens**. Starting at low power gives a wider view, so it is easier to locate the cells.\n\nThis first positioning step earns **B1**.","highlights":[{"text":"starting with the slide placed on the stage","location":"specification"}]},{"type":"text","order":1,"title":"Focus safely at low power","content":"Look from the side and use the coarse-focus knob to move the stage upwards, stopping before the objective lens can crush the slide. Now look through the eyepiece and slowly lower the stage until the specimen comes into focus.\n\nThe safety check, correct knob, and focusing sequence together earn **M1**.","highlights":[{"text":"locate, and focus on these plant cells under high power magnification","location":"specification"}]},{"type":"text","order":2,"title":"Switch and sharpen","content":"Rotate the nosepiece to the **high-power objective lens**. At high power, turn **only the fine-adjustment knob** to sharpen the image. Continue until the cell walls and nuclei are clear and sharply focused.\n\nThis final high-power focusing step earns **A1**.","highlights":[{"text":"cell walls and nuclei","location":"specificati

Cells and microscopy

Question 4

Cells and microscopy Questions

Cells and microscopy

Question 4

Cells and microscopy Questions