Which of the following associations regarding the primary mechanism of action of
ID: 82243 • Letter: W
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Which of the following associations regarding the primary mechanism of action of antimicrobial agents is INCORRECT? Streptomycin-inhibits protein synthesis by causing misreading of the genetic code Sulphonamides -inhibit protein synthesis by interfering with the action of peptidyl transferase. Penicillin G-inhibits synthesis of a key component of bacterial cell walls Vancomycin-inhibits synthesis of the same cell wall component as penicillin G, but in a different way The activation of T and B cells is the central process of the adaptive immune system. Which one of the following statements describing features of the activation process that are shared by both T cells and B cells is CORRECT? Both B cells and T cells express MHC class ll molecules that act as co-stimulatory molecules An individual T cell or B cell may be activated by many different antigens The same part of the antigenic molecule is recognized by both B cell receptor and T cell receptor B cells and T cells both circulate through lymphoid tissues where they encounter antigen Which one of the following statements regarding innate immunity is INCORRECT? Toll-like receptors (TLRs) are able to discriminate between the foreign antigens present on individual microbes. The cells of the innate immune system are activated by binding molecular patterns that are present on microbes and in certain circumstances on host cells Innate immunity can be divided into recognition, activation and effectors phases The innate immune system can protect against intracellular and extracellular microorganisms. Which of the following statements regarding the outcome of triggering of the complement cascade is INCORRECT? Triggering of the complement cascade results in: Opsonisation of bacteria. Lysis of IgG coated bacteria Lysis of IgA coated bacteria Neutrophil chemotaxis. Which one of the following statements regarding MHC class I molecules is CORRECT? MHC class I molecules: Are expressed on antigen presenting cells Bind only intracellular pathogen derived peptides Are generated through random somatic gene rearrangements Display antigenic peptides obtained from endosomal antigens.Explanation / Answer
22. B. Sulphonamides do not inhibit protein synthesis by interfering with the action of peptidyl transferase. They block the synthesis of the folate needed for DNA replication.
23. A. Both B cells and T cells express MHC II molecules that act as co-stimulatory molecules. Since, MHC II is expressed by antigen presenting cells such as macrophages, B-Cells, and dendritic cells only.
24. C. The recognition, activation and effector phases are the stages of adaptive immunity.
25. C. The IgA coated bacteria escapes the action of complement cascade
26. C. MHC are generated by the degradation of cytosolic proteins by the proteasome
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