Bacteria may be grouped by the kind of cell wall they possess. Gram-negative bacteria possess a cell wall with an outer layer called the outer membrane. Gram-positive bacteria lack an outer membrane, but their peptidoglycan layer is much thicker than that of Gram-negative bacteria. Fig. 4.1 shows a diagram of part of the cell wall of a Gram-negative bacterium. Both pathogenic and non-pathogenic Gram-negative bacteria are able to form extracellular vesicles. Fig. 4.2 outlines the way two forms of extracellular vesicle, OMVs and O-IMVs, are produced. O-IMVs arise from the outer membrane and the cell surface membrane. O-IMVs may include ATP and DNA.
(a)[3]
Using Fig. 4.1, describe the similarities and differences between the outer membrane of a Gram-negative bacterial cell and the cell surface membrane of a eukaryotic cell.
(b(i))[1]
Using Fig. 4.2, propose why fewer O-IMVs are formed than OMVs.
(b(ii))[1]
Suggest why ATP is found within O-IMVs but not in OMVs.
(b(iii))[2]
Suggest and explain why the discovery that O-IMVs contain DNA has implications for antibiotic resistance.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “similarity: both include phospholipids” …