7. (a) State a use of each of the following in the biology laboratory - Leaving Cert Biology - Question 7 - 2019
Question 7
7.
(a) State a use of each of the following in the biology laboratory.
(i) Biuret reagent (a solution containing copper sulfate and sodium hydroxide).
(ii) Bened... show full transcript
Worked Solution & Example Answer:7. (a) State a use of each of the following in the biology laboratory - Leaving Cert Biology - Question 7 - 2019
Step 1
State a use of Biuret reagent (a solution containing copper sulfate and sodium hydroxide).
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Answer
The Biuret reagent is primarily used to test for the presence of proteins in a solution. When proteins are present, the solution will change color, indicating a positive result.
Step 2
State a use of Benedict's (or Fehling's) solution.
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Benedict's solution is used to test for reducing sugars. A positive test results in a color change, typically from blue to green, yellow, or brick red, depending on the amount of reducing sugar present.
Step 3
When preparing a sample of cheek cells on a microscope slide, why did you: Place a coverslip over the cells?
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A coverslip is used to prevent the cells from drying out and to protect the objective lens from water or stains. It also helps in making the sample easier to observe.
Step 4
When preparing a sample of cheek cells on a microscope slide, why did you: Apply methylene blue to the cells?
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Methylene blue is used to stain the cells, making them more visible under the microscope. This helps to enhance contrast and detail.
Step 5
When extracting DNA from plant tissue, why did you: Washing-up liquid?
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The washing-up liquid helps break down cell membranes, allowing the release of DNA from the plant cells.
Step 6
When extracting DNA from plant tissue, why did you: Freezer-cold ethanol?
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Freezer-cold ethanol is used to precipitate the DNA, making it visible by separating it from the solution.
Step 7
When using seeds to investigate the effect of IAA on plant tissue, why did you: Carry out a serial dilution of an IAA solution?
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Serial dilution is performed to create solutions of varying concentrations of IAA, which will allow for the assessment of its effects on plant tissues.
Step 8
When using seeds to investigate the effect of IAA on plant tissue, why did you: Place the seeds on a grid in Petri dishes?
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Placing the seeds on a grid allows for accurate measurements of the root or shoot growth under controlled conditions.
Step 9
When carrying out an activity to investigate osmosis: Why did you use Visking™ tubing?
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Visking™ tubing acts as a selectively permeable membrane, simulating the behavior of plasma membranes in cells.
Step 10
When carrying out an activity to investigate osmosis: How did you know osmosis had taken place?
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Evidence of osmosis is observed through changes in the mass of the tubing, which may increase or decrease, indicating water movement. Additionally, increased turgidity in plant cells signals water uptake.
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