I think they want you to think about how conjugate vaccine is made: polysaccharide + protein fragment (to induce T dependent immune response). Only flagellin is a protein (or at least sounds like one) in the option list.
This is what I thought but not sure if it’s correct. There is a UWorld q where it describes co-administration of cortisol and epinephrine. Cortisol significantly enhances the effect of epi because cortisol has a permissive effect on maintaining the adrenergic receptors.
I think it has something to do with glycine (due to its small size it can fit in many places where other amino acids can not and hence it provides “structural compactness” to the collagen, i.e. put a kink in the alpha helix). If glycine is misplaced by something else, I don’t think pro-collagen can form its correct secondary structure.
Syphilis pathogenesis is the inflammation and obliteration of the vasa vasorum (small blood vessels) that feeds bigger blood vessels like aorta, arteries, arterioles. It does not matter what the stage is, T. pallidum infects the vasa vasorum and, in the process, obliterates the nerves and blood vessels. This kills blood supply to those areas = ischemia but no pain (painless chancre). More localized in earlier stages, and in later stage, the spirochetes disseminate, so you have the aorta and spinal cord involvement but same pathogenesis. (Edit: Goljan explained this somewhere.)