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Describe how the scientists could use aseptic techniques to transfer 0.3 cm³ of C - AQA - A-Level Biology - Question 8 - 2022 - Paper 1
Question 8
Describe how the scientists could use aseptic techniques to transfer 0.3 cm³ of C. difficile in liquid culture from a bottle onto an agar plate.
Worked Solution & Example Answer:Describe how the scientists could use aseptic techniques to transfer 0.3 cm³ of C - AQA - A-Level Biology - Question 8 - 2022 - Paper 1
Step 1
Use Aseptic Techniques for Transfer
Answer
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Preparation of Work Area: Ensure that the workspace is clean, preferably working in a sterile environment such as a laminar flow hood. Use disinfectants to wipe the surfaces and eliminate any potential contaminants.
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Sterilization of Equipment: Gather the required equipment, including a sterile pipette or inoculating loop. Sterilize the pipette or loop by placing it in a flame until it glows red-hot, then allow it to cool before use.
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Inoculation: Open the bottle containing the C. difficile culture while minimizing exposure to the air. Use the sterile pipette to draw out exactly 0.3 cm³ of the liquid culture, then quickly seal the bottle again. Use the pipette to transfer the culture onto the agar plate, spreading it gently to ensure even distribution while avoiding contamination.
Step 2
Give two features of all prokaryotic cells that are not features of eukaryotic cells.
Answer
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Prokaryotic cells lack a nucleus and do not contain DNA organized into chromosomes; instead, their genetic material is circular and free-floating in the cytoplasm.
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Prokaryotic cells lack membrane-bound organelles and are generally smaller than eukaryotic cells.
Step 3
Step 4
Suggest how these properties of the APs allow them to become positioned across the membrane.
Answer
The amino acids on one side of the AP helix possess hydrophobic properties, allowing them to interact favorably with the lipid bilayer of the membrane. This hydrophobic interaction helps anchor the APs within the membrane. Conversely, the amino acids on the opposite side, possessing hydrophilic properties, are able to interact with the aqueous environment on either side of the membrane. This arrangement allows the APs to span the membrane effectively, forming a channel through which ions or molecules can pass.