Medicinal and Pharmaceutical Chemistry Exam 1 with answers.

Medicinal and Pharmaceutical Chemistry \| \| \| \|




Exam 1 with answers \| \| \|




The hormone adrenaline interacts with proteins located on the surface of cells
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and down not cross the cell membrane. However, larger steroid molecules,
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such as estrone, cross cell membranes and interact with proteins located in
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the call nucleus. Why is a large steroid molecule able to cross the cell
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membrane when a smaller molecule such as adrenaline cannot? - CORRECT
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ANSWERS ✔✔The ability of a molecule to cross the fatty cell membrane has
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little to do with its size, but more with its hydrophobic character.
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Estrone is more hydrophobic than adrenaline since it has a larger carbon
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skeleton and only two polar functional groups. Thus, the molecule is
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hydrophobic in character and can dissolve through the fatty cell membrane.
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Adrenaline has four polar functional groups and a much smaller carbon
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skeleton. Thus the polar functional groups dominate in determining the
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character of the molecule making it very polar and unlikely to pass through
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the cell membrane.
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Valinomycin is an antibiotic which is able to transport ions across cell
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membranes and disrupt the ionic balance of the cell. Find out the structure of
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valinomycin and explain why it is able to carry out this task. - CORRECT
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ANSWERS ✔✔outside is hydrophobic and inside is hydrophilic. as a result, it
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can easily pass through the cell membrane and encapsulate polar ions;
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Archea are microorganisms that can survive in extreme environments, such
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as high temperatures, low pH, or high salt concentrations. It is observed that
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, the cell membrane phospholipids in these organisms are markedly different
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from those in eukaryotic membranes. What differences are present and what
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function might they serve? - CORRECT ANSWERS ✔✔The alkyl chains are
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linked to the glycerol skeleton by ether linkages rather than by ester linkages.
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Ethers are chemically more stable than esters to extreme conditions.
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The long alkyl chains are also branched, unlike those in eukaryotic cell
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membranes. Branching makes the chains more resistant to oxidation. \| \| \| \| \| \| \| \|




Teicoplanin is an antibiotic which 'caps' the building blocks used in the
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construction of the bacterial cell wall such that cannot be linked up. The call
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wall barrier surrounding the bacterial cell membrane and the building blocks
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are anchored to the outside of this cell membrane prior to their incorporation
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into the cell wall. Teicoplanin contains a very long alkyl substituent which
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plays no role in the capping mechanism. However, if this substituent is
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absent, activity drops. What role do you think this alkyl substituent may
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serve? - CORRECT ANSWERS ✔✔The alkyl group is hydrophobic and is
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embedded into the cell membrane. As a result, the drug is anchored to the cell
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membrane and is located on its outer surface such that it is ideally located to
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interfere with cell wall synthesis. \| \| \| \|




The Rao protein is an important protein in signaling processes within the cell.
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It exists freely in the cell cytoplasm, but must become anchored to the inner
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surface pf the cell membrane in order to carry out its function. What kind of
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modification to the protein might take place to allow this to happen? - \| \| \| \| \| \| \| \| \| \| \| \| \|




CORRECT ANSWERS ✔✔A hydrophobic chain could be attached to the Ras
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protein which would serve to anchor it to the inner surface of the cell
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membrane, in the same way in which teicoplanin is anchored to the outer
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surface of cell membranes (compare answer 5 above). The actual process by
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which a hydrophobic chain is attached to the Ras protein is shown below
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where the chain is attached to a cysteine residue.
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