Give two features of all prokaryotic cells that are not features of eukaryotic cells - AQA - A-Level Biology - Question 3 - 2022 - Paper 1

✔ Hydrogen

The hydrophobic amino acids on one side of the AP helix interact favorably with the hydrophobic core of the membrane, allowing the AP to embed within it. Conversely, the hydrophilic amino acids on the other side interact with the aqueous environment, facilitating the formation of a channel through which ions can easily pass.

To calculate the cross-sectional area (A) of a circular channel, use the formula:
A = rac{oldsymbol{ ext{π}} imes d^2}{4}
Given the diameter (d) is 1.1 m, substituting in oldsymbol{3.14} for π:
A = rac{3.14 imes (1.1)^2}{4} = rac{3.14 imes 1.21}{4} = rac{3.7994}{4} = 0.94985
Therefore, the cross-sectional area is approximately 0.9 mm² (to 1 decimal place).

1. Eukaryotic cells have membranes stabilized by cholesterol, which provides structural support, unlike prokaryotic cells.
2. Antimicrobial polypeptides target the specific membrane lipids found in prokaryotic cells that are absent in eukaryotic membranes.
3. Eukaryotic cells also possess other protective mechanisms that prevent AP uptake or effect.

1. The use of antibodies specific to the AP allows for targeted staining of these molecules.
2. The gold particles attached to the antibodies provide high electron density, making the APs more visible under a transmission electron microscope.
3. The binding of antibodies increases contrast and helps highlight the location and structure of the APs on prokaryotic cells.