Consider which specific substance is used to detect polysaccharides rather than simple sugars or proteins.

Iodine solution as it turns blue-black

Ethanol solution as it turns dark green

Benedict solution as it turns brick red

Biuret reagent as it turns light purple

Think about what happens to the view through a microscope when small pockets of gas are present between the slide and the cover.

To prevent air bubbles trapped under

To ensure cells do not dry out fast

To protect the glass from breakage

To make the light focus more clear

AQA GCSE Biology

Required practicals — biology

AQA GCSE Biology revision on Required practicals — biology. Aligned to the AQA GCSE Biology 8461 specification. This bank has 25 practice questions on this topic.

Sample questions (3 of 25)

Question 1

Which chemical reagent is used to identify the presence of starch in a food sample during the food test practical?
- A) Iodine solution as it turns blue-black
- B) Ethanol solution as it turns dark green
- C) Benedict solution as it turns brick red
- D) Biuret reagent as it turns light purple
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Answer: Iodine solution as it turns blue-black

Iodine solution is the correct reagent for starch, which causes the liquid to change from orange-brown to blue-black. Benedict solution is used for sugars, and Biuret is used for proteins, which are common distractors for students to confuse.
Question 2

What is the calculated magnification if an image of a cell measures 40 millimetres and the actual size of the specimen is 0.05 millimetres?

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Answer: 800

The magnification is calculated by dividing 40 by 0.05, which equals 800. Students often mistakenly multiply the values instead of dividing, or fail to convert units if they were provided in different scales.
Question 3

Why must the coverslip be lowered at an angle onto the slide when preparing a specimen for light microscopy?
- A) To prevent air bubbles trapped under
- B) To ensure cells do not dry out fast
- C) To protect the glass from breakage
- D) To make the light focus more clear
Show answer

Answer: To prevent air bubbles trapped under

Lowering the coverslip at an angle is a standard technique to prevent air bubbles from becoming trapped, as these can be easily mistaken for cellular structures. The other options describe general slide care but do not explain the purpose of the angled movement.

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