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Molecules and Drugs

Question 1

(a)

The chemical forumla is C5H9N3.

(b)

(c)

N-H which is the ability to form hydrogen bonds with water.

Question 2 

(a)

C16H21N3

(b)

The similarities are a two-carbon chain with a nitrogen at the end and a three-atom sequence of N-C-N, the spatial placement of these pieces, and the flat 5-ring of histamine can also be considered similar to the flat 6-ring of the antihistamine.

Question 3

Drugs that produce a physiological response in the body 
  • Aspirin
  • Morphine
  • Estrogen
  • Amphetamine
Drugs that inhibit the growth of substances that cause infections
  • (Keflex) antibiotic
  • Penicillin

Question 4 

(a)

Herbal supplement manufacturers provide labels on their products regarding ingredients used and whether it has complied with the relevant regulatory authorities’ standards.

Advice on dosage and usage compatibility are also provided within the package of the product itself.

(b)

Singapore has Traditional Chinese Medicine Practitioners Act (Chapter 333A), Health Products Act, Medicines Act, Poisons Act, and the Health Science Authority of Singapore (HSA) has issued guidelines regarding the use of traditional medicine materials.

Traditional Chinese Medicines are regulated by HSA and manufacturers must comply with a set of safety and quality criteria before thy are allowed to be sold.

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The World of Polymers and Plastics

Question 1

Acetone dissolves the polymer, allowing the gas of the foaming agent to escape. The polymer collapses on itself and is denser because the gas has been removed.

Question 2 (a)

LDPE cannot be used in this application because it does not have the required strength.

Question 2 (b)

The molecules of HDPE must line up in a way that produces the required strength. Using a thin liner of HDPE allows sufficient flexibility.

Question 3

When the piece of plastic is stretched, the strip narrows and “necks down.” The molecules become aligned parallel to each other and in the direction of the pull. This alteration of the three-dimensional structure is not reversible, and if the pulling continues, the plastic breaks. When the same pulling force is applied to a piece of paper, the paper tears rather than stretching to any significant extent. The cellulose molecules in a paper are held far more rigidly in place and are not free to become aligned.

Question 4 (a)

The benefits for polymers intended for use in the body should far outweigh any risks. The two main properties are (1) stable over time of intended use and (2) non-toxic. Other factors to consider are low cost, lack of solubility in body fluids, lack of reactivity in body fluids, and the ease of implantation.

Question 4 (b)

(b)  Several different types of contact lenses are on the market and each uses a different type of polymer. Polymethyl methacrylate (PMMA), one of the earliest polymers used for rigid gas permeable lenses, is structurally similar to Lucite and plexiglas. Silicone-acrylate materials now are more commonly used under trade names such as Kolfocon. Newer rigid gas permeable (RGP) polymers contain fluorine: fluoro-silicone-acrylate polymers and fluoro-silicones. Polymacon (38% water) is typical of the polymers used for soft lenses and is a polymer of 2-hydroxyethyl methacrylate (HEMA). Other methacrylates include hioxifilcon (48% water) and methafilcon (55% water) or even lidofilcon (70% water). Manufacturers’ websites are good sources of information. Desirable properties include being nontoxic, permeable to oxygen, comfortable to wear, and inexpensive. Also desirable is the ability to conform to the shape of the eye and to be easily cleaned (if not disposable).

Question 4 (c)

As mentioned in the previous part, hard contact lenses are typically made of PMMA, a rigid non-gas permeable plastic. The soft contact lenses that replaced them are made of silicone, which is flexible and allows oxygen to reach the eye. Because of these properties, the soft lenses tend to be more comfortable.