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Give two features of all prokaryotic cells that are not features of eukaryotic cells - AQA - A-Level Biology - Question 3 - 2022 - Paper 1
Question 3
Give two features of all prokaryotic cells that are not features of eukaryotic cells. 1 2 Many multicellular organisms produce antimicrobial polypeptides (APs) th... show full transcript
Worked Solution & Example Answer:Give two features of all prokaryotic cells that are not features of eukaryotic cells - AQA - A-Level Biology - Question 3 - 2022 - Paper 1
Step 1
Step 2
Step 3
Suggest how these properties allow them to become positioned across the membrane (as shown in Figure 3) and make a channel through which ions can pass.
Answer
The hydrophobic amino acids of the polypeptide prefer to interact with the lipid bilayer, allowing them to insert themselves into the membrane, while the hydrophilic amino acids face the aqueous environment. This arrangement helps to form a stable channel across the membrane, facilitating ion passage.
Step 4
Use Figure 5 to calculate the cross-sectional area of the channel through which ions can pass.
Answer
The diameter of the channel is stated as 1.1 m. Using the formula for the area of a circle, A = πr², we find:\n1. Radius = 1.1 m / 2 = 0.55 m.\n2. Area = 3.14 * (0.55 m)² = 0.953 m², which is 953,000 mm² (to 1 decimal place, 953000.0 mm²).
Step 5
Assess why the APs do not damage the eukaryotic cells of the organisms that produce them.
Answer
- Eukaryotic membranes contain cholesterol which stabilizes the membrane structure, making it more resistant to damage from APs.\n2. APs typically target specific prokaryotic features that are absent in eukaryotic cells, allowing them to pass through eukaryotic cell membranes without damaging them.
Step 6
Suggest how these techniques allowed observation of APs on prokaryotes.
Answer
The use of a transmission electron microscope, combined with the staining of APs using a monoclonal antibody tagged with gold, enhances contrast. The gold particles scatter electrons, making APs visible during imaging, thus allowing scientists to observe these structures directly on prokaryotic cells.