t was not until 13 years later that penicillin was used on humans. This discovery has saved many lives, but as time progressed scientist discovered that there was still some bacteria that were resistant to penicillin. Antiviral Drugs- in contrast to bacteria, viruses require the machinery of a host cell to reproduce. A virus, which usually consists of only DNA and protein, takes over a host cell and inserts its own DNA into the chromosomes of the host. This virus uses the host cell to produce more viruses. The new viruses infect other host cells and the cycle repeats. Viruses unfortunately do not respond to antibiotics.Until recently the only way to fight viruses was to prevent them through vaccination, a process that uses the body to fight the disease. A vaccination consists of introducing a small number of inactivated viruses into the body, usually through injection. The body then develops antibodies to the virus, which remain in the body and are available to fight off the disease should infection with the real virus occur.Sex Hormones and the Pill- Sexual characteristics are managed by molecules called hormones, chemical messengers that act on target cells usually located a long distance from where the hormone are secreted. The male sexual hormones, called androgens, are secreted primarily by the testes. The most important and powerful androgen is testosterone, which acts before the birth of a male infant to form the male sex organs. Testosterone acts again at puberty and beyond to promote the growth and maturation of the male reproductive system, to develop the sexual drive, and to determine secondary sexual characteristics such as facial hair and voice deepening.The female sex hormones are called estrogen and progesterone and are secreted primarily by the ovaries. Unlike testosterone, estrogen and progesterone are released in cyclical patterns. Estrogen in the female, like testosterone in the male, causes maturation and maintenance...
