Hi Nicole,
Q8) "The plasma membrane-embedded domain of the angiotensin I converting enzyme 2 (ACE2) is necessary for AT1 localization to the luminal plasma membrane of small intestinal epithelial cells."
Q21) Its hard to tell the size of a molecule from a 2D image of its structure. I would say its more reliable to use polarity in this case to determine whether it can simply diffuse. STN has several cyclic rings which would indicate its hydrophobic/lipophilic, allowing it to diffuse directly through the membrane.
Q26) This question would be easier with the knowledge of lipid rafts, however, you can also approach the question through the lens of glycoproteins being found on both sides of the membrane. A,B, and C all point to one side over another which through the process of elimination can give you D.
As for Q27, oligosaccharide is a terminology that you should know from Orgo. So I'd definitely go back and revisit your notes.
Q32) B is wrong because to form a peptide bond you need the primary carboxyl group and amino group of the AA, which ornithine has, so it can form a peptide bond. C is wrong because the passage does not talk about the dietary availability of ornithine, so we're making assumptions here. D is wrong because having a net positive charge in aqueous solutions has nothing to do with its ability to be incorporated into protein. We have several AAs (like lysine and arginine) that are also positively charged in aqueous solutions but are incorporated into proteins.
Q38) If there are increased concentrations of any protein, it is not due to more DNA sequences since the amount of DNA we have is finite after we're born, we don't add DNA as we encounter toxins, so A would be wrong. rRNA forms part of the ribosomes, and having more of it will not increase cP-450 levels since you need the substrate, i.e. mRNA coding cP-450, to process it and increase its levels, so C is wrong. Having more cysteine-specific tRNA will again not increase the levels of cP-450, because we need more mRNA to be translated so that tRNA containing cysteine can be added, so D is wrong.
Q39) If previous abuse of alcohol had inhibited cP-450 activity, less of the barbituates would be metabolized so more of the effect would be felt, i.e. he would feel drowsy.
Q52) Yes, glycolytic a.k.a. breakdown of glucose
Q57) After the first round, one strand will have 15N and the other strand 14N. Now going into the second round of division, the strands will separate and replicate (synthesis phase of cell cycle) so you will have one chromosome with 15N and 14N sister chromatids and another chromosome with 14N and 14N sister chromatids. Once you go through cytokinesis, half of the cells will have the 14N exclusive genome and the other half the mixed genome.
Hope this helps :)