A student prepared some onion cells - AQA - GCSE Biology - Question 3 - 2022 - Paper 1
Question 3
A student prepared some onion cells.
The student viewed the onion cells using a light microscope.
Table 4 shows a risk assessment for this experiment.
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Worked Solution & Example Answer:A student prepared some onion cells - AQA - GCSE Biology - Question 3 - 2022 - Paper 1
Step 1
Hazard: Iodine solution is an irritant
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Answer
Iodine solution is used because it helps to stain the parts of the cell, including sub-cellular structures such as the nucleus, cytoplasm, and cell wall. This enhances visibility under the microscope.
Step 2
Hazard: Iodine solution is added to the onion epidermis.
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Answer
Adding iodine solution stains cellular components which makes them more visible, allowing for a clearer observation of the onion cells' structure.
Step 3
Hazard: The cover slip is lowered onto the onion epidermis at an angle.
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Lowering the cover slip at an angle helps to prevent the formation of air bubbles that can obscure the view of the onion cells under the microscope.
Step 4
The length of cell Z in Figure 3 is 4.8 cm.
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Answer
To calculate the real length of cell Z, we use the formula:
ext{magnification} = rac{ ext{size of image}}{ ext{size of real object}}
Where the magnification can be calculated as:
ext{size of real object} = rac{ ext{length of image} imes 400}{4.8}
Substituting the values:
ext{size of real object} = rac{4.8 imes 10000}{400} = 120 \text{ μm}
