microbiology chapter 12 test bank

Correct Answer: C

Rationale: The correct answer is C: Inhibits protein synthesis. Exotoxin of C. Diphtheriae acts by inhibiting protein synthesis in host cells. This disrupts cellular functions and leads to tissue damage. Choice A is incorrect because acetylcholine release is not affected. Choice B is incorrect as it does not involve neurotransmitters. Choice D is incorrect as the exotoxin does have a specific mechanism.

Correct Answer: A

Rationale: The correct answer is A, proportion 4:1. Gram (+) bacteria have a higher ratio of MG-ribonucleate to Mg. deoxyribonucleate because ribosomal RNA is more abundant in actively growing bacterial cells. This higher proportion of MG-ribonucleate to Mg. deoxyribonucleate is essential for protein synthesis and growth. The other choices are incorrect because they do not reflect the higher ratio of ribosomal RNA to DNA in Gram (+) bacteria, which is crucial for their metabolic activities and cellular functions.

Correct Answer: C

Rationale: The correct answer is C: Inhibits protein synthesis. Exotoxin of C. Diphtheriae acts by inhibiting protein synthesis in host cells. This disrupts cellular functions and leads to tissue damage. Choice A is incorrect because acetylcholine release is not affected. Choice B is incorrect as it does not involve neurotransmitters. Choice D is incorrect as the exotoxin does have a specific mechanism.

Correct Answer: D

Rationale: The correct answer is D: Non-tender chancre (ulcus durum). In the primary stage of syphilis, an individual typically develops a painless ulcer known as a chancre at the site of infection. This ulcer is usually firm, round, and clean with well-defined borders. It is important to note that it is non-tender, which distinguishes it from other skin conditions. This characteristic helps healthcare providers differentiate syphilis from other sexually transmitted infections. Explanation for other choices: A: Diffuse maculopapular rash - This is more commonly associated with secondary syphilis. B: Purulent exudation from the urethra - This is not a typical presentation of primary syphilis. C: Syphilitic granulomas (gummas) - Gummas typically develop in the tertiary stage of syphilis, not in the primary stage.

Correct Answer: D

Rationale: The correct answer is D: Multiplies by binary fission. Bacterial cells reproduce through binary fission, where a single cell divides into two identical daughter cells. This process is essential for bacterial growth and multiplication. A: The oxidative phosphorylation does not take place in the mitochondria of bacterial cells but in the cell membrane. B: Capsules are not organelles but outer protective layers found in some bacterial cells. C: Bacterial cells contain both DNA and RNA, essential for their genetic information and protein synthesis.