Sk 185 - Molecules, Medicines and Drugs

SK185 Molecules, Medicines and Drugs

End of Course Assessment 31st July 2007

Question 1

a) The early testing stage for potential drugs is required for many reasons.

Firstly, tests are performed to discover if the drug is effective i.e. does it work. If the drug does work the next stage of testing can proceed because it is a possible treatment and could be profitable.

Next, pharmaceutical companies conduct tests to understand the effects of high doses and long-term usage of the drug. Such tests enable companies to see if the drug is harmful in both instances. Also tests are performed to what side effects the potential drug has.

During the two years these tests are carried out on animals. Testing on animals protects humans from the possible, unknown side effects a new drug may have. Animals used in these tests range from rodents to larger mammals; the latter allowing scientists to more accurately predict the effects of the drug on humans.

Other tests carried out in the two year testing stage include chemical analysis to find the drug's molecular formula. The functional groups that make the drug an effective treatment for an illness are identified. This allows an optimum drug to be made i.e. one that provides the best treatment of a disease.

b) Non-polar molecules are neutral i.e. they have no charge. Polar molecules contain partial, opposite charges

Polarity arises in molecules containing covalent bonds, which form when two atoms share a pair of electrons. Electronegativity is a measure of an atom's power to attract this bonding pair of electrons. In covalent bonds atoms with higher electronegativity attract the electrons, gaining a slight negative charge. The atom with lower electronegativity becomes electron deficient with a slight positive charge.

In bonds containing atoms of similar electronegativity no partial charges are formed because neither atom attracts the bonding electrons - a non-polar molecule is formed.

Hydrogen Fluoride is a polar molecule:

Methane is non-polar molecule:

c) Captopril:

d) Influenza vaccines are limited in the protection they provide.

This is because the influenza virus mutates, creating new forms of the disease. Vaccines are created to treat known strains of the virus and when new strains appear due to mutation, the vaccine is ineffective against these types of the virus.

Bacterial infections are easier to combat than viral infections because of the differences in each type of cell's mode of reproduction. Bacteria replicate by the division of one cell into two cells (mitosis). Antibiotics are used to treat bacterial infections by preventing the cells from replicating. However, because viruses use the body's cells as hosts to create more viral cells, antibiotics have no effect on such infections.

After viral cells are produced in the host cell, they escape using enzymes to break through the cell membrane. Cures for infection centre on the use of inhibitors to block these enzymes' active sites thus preventing new viruses from leaving the host. Difficulties arise when finding inhibitors, which fit the active site for all strains of the virus. The search for cures for influenza is less successful because effective inhibitors are more difficult to produce than drugs to treat bacterial infections.

Question 2

a)

i) Structure A is likely to be more active than penicillin against bacteria.

ii) Structure B is likely to be less active than penicillin against bacteria.