Answer the following in relation to some laboratory investigations that you carried out - Leaving Cert Biology - Question b - 2021
Question b
Answer the following in relation to some laboratory investigations that you carried out.
(i) When conducting qualitative food tests:
1. What reagent or chemicals d... show full transcript
Worked Solution & Example Answer:Answer the following in relation to some laboratory investigations that you carried out - Leaving Cert Biology - Question b - 2021
Step 1
1. What reagent or chemicals did you use to test for the presence of protein?
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Answer
To test for the presence of protein, the primary reagent used is Biuret solution, which consists of copper sulfate (CuSO₄) and sodium hydroxide (NaOH). This solution reacts with the peptide bonds in proteins.
Step 2
2. What colour indicates the presence of protein in a food sample?
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Answer
The presence of protein in a food sample is indicated by a purple or lilac color when Biuret solution is added.
Step 3
1. Why did you chop the tissue?
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Chopping the tissue helps to break or disrupt the cell walls, allowing cytoplasm to leak out and increasing the surface area for subsequent reactions.
Step 4
2. Why did you add salt to the chopped tissue?
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Answer
Salt was added to help the DNA clump or protect it from being degraded by proteins during the extraction process.
Step 5
3. Why did you add washing up liquid to the chopped tissue and salt?
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Washing up liquid was added to break down the cell membranes (both nuclear and cellular) and to release DNA from the nucleus into the solution.
Step 6
4. Describe how the DNA was then isolated from this solution.
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To isolate the DNA, the solution was first cooled for 3 seconds. Then, protease (or a named protease) was added to break down proteins. Afterward, ethanol was added, which helps to precipitate the DNA, making it visible. The DNA can then be removed from the solution.
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