BIOL 221

Penicillin was considered a "miracle drug" for which of the following reasons? correct answer: It was the first antibiotic it does not affect eukaryotic cells It has selective toxicity It kills bacteria Most of the available antimicrobial agents are effective (useful) against: correct answer: Bacteria In what ways are semisynthetic penicillins and natural penicillins alike? correct answer: Both are based on B-lactam More than half of our antibiotics are: correct answer: Produce...

The most frequently used portal of entry that can cause Hepatitis A is the: correct answer: Mucus membranes of the respiratory tract. The ability of some microbes such as Trypanosoma or Giardia to alter their surface molecules and evade destruction by the hosts antibodies is called: correct answer: Antigenic variation. Which of the following statements is TRUE? -IgA proteases can destroy IgA antibodies. -Hemolysins lose red blood cells. -leukocidins lose white blood cells. -hemolys...