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Question 121 (part 2) · LDEK · Etiology and pathogenesis of caries

Choose true statements:

1) bacteria metabolizing carbohydrates to butyric or propanoic acidify the environment less than bacteria which produce acetic, lactic and formic acid;
2) synthesis of intracellular polysaccharides is one of defense mechanisms of S. mutans in a situation of high supply of carbohydrates in diet;
3) in aerobic conditions S. mitis and S. sanguis produce hydrogen peroxide and ethanol under influence of pyruvate dehydrogenase;
4) in anaerobic conditions and low supply of carbohydrates in diet streptococci, lactic acid bacilli and actinomyces produce formic and acetic acid and ethanol via formate lyase pathway;
5) in a situation of high and stable supply of carbohydrates, oral cavity is dominated by S. sanquis and S. salivarius .
Correct answer is:
  1. A. 3,4,5.
  2. B. 2,3,5.
  3. C. 1,3,5.
  4. D. 1,4,5.
  5. E. 1,2,4.
Hint

Compare the strength of the acids produced, think which metabolic products arise with and without oxygen, and which species a sugar-rich diet favours.

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