Question

Exam 2 Micro Spring Form A Page 7 54. The human stomach normally contains few organisms because of the A. rapid emptying of the stomach B. churning action of the stomach c. antiseptie action of the saliva D. disinfectant action of the acid media 55. Which ONE of the following structures protects the procaryotic call from phagocytosis: A. capsule B. cell membrane c. cell wall D. flagella E none of these apply 56. During this period, the rate of growth is equal to the rate of death: A. stationary phase B. lag phase c. decline D. los phase 57. Which one of the following diseases is caused by an endospore forming bacterium: A. typhoid fever B. tuberculosis c. tetanus D. trichinosis 58. A. Chemically, exotoxins primarily consist of: lipid B. protein C. lipopolysaccharides nucleic acids none of the above D. nu 59. The hemolytic activity of Streptococci is due to hemolysins which are called: A. leukocidins B. streptokinases c. hyaluronidases D. streptolysins E none of the above 60. At the most active period of multiplication in cultures, cell division commonly exceeds cell growth, so that individual cells relatively: A. pleomorphic B. involuted C. large D. Small E none of the above 61. The chemical transformations carried out by an organism whereby organism synthesizes cell wall material is called: A. anabolism B. catabolism c. antibiosis D. metabolism E. all of these apply

Answer 1

54. (D) Disinfectant action of the acid media. In the stomach, Oxyntic cells (also called Parietal Cells) secrete HCl which keeps the stomach highly acidic (pH 1.5 - 2.5). As a result, very few organisms can survive in the stomach.

55. (A) Capsule. It's a polysaccharide layer outside the cell membrane of a bacterium, mainly composed of peptidoglycan. It prevents the bacteria from engulfment by macrophages. A capsule-specific antibody is required for phagocytosis to take place.

56. (A) Stationary phase. As the rate of growth is equal to the rate of death, the size of the population remains constant.

57. (C) Tetanus. Tetanus is caused by Clostridium tetani which produce round, terminal endospore (Drumstick shape).

58. (B) Protein. Exotoxin is mainly protein that is secreted by different bacteria. Endotoxins are chemically lipopolysaccharides.

59. (D) Streptolysin. Streptococcus secretes streptolysin that has the hemolytic ability and can be seen forming colonies on blood agar.

60. (D) Small. As the cells divide quickly, it gets very less time to grow. As a result, the cells should become small in size.

61. (A) Anabolism. Anabolism is a chemical process by which a living organism forms complex molecules fro simpler ones. The cell wall is commonly made of complex molecules (Peptidoglycan/Cellulose/Hemicellulose/Chitin).