Name ID MULTIPLE CHOICE. Choose the one alternative that best completes the stat

Question

Name ID MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1)hhich is sensitive to penicillin treatment? A) Mycoplasma B) Thermoplasma. C) protoplast D) Staphylococcus aureus E) spheroplast. 2) Benicillin A) inhibits the formation of NAG-NAM precursor of peptidoglycan synthesis. B) inhibits the activity of transglycosylases in peptidoglycan synthesis. C) stimulates the activity of transpeptidase in peptidoglycan synthesis. D) inhibits the formation of peptide cross-bridges in E) does none of the above. doglycan. 3) Acid-fast stain must be used to stainMycobacterium and Norcadia because they have A) teichoic acids. B) periplasm C) hydrophobic outer membrane. D) thick peptidoglycan layer. E) mycolic acid. opeptidoglycan is a characteristic of the walls of A) Eukarya. B) some Bacteria and Archaea. C) Bacteria and Archaea D) Bacteria. E) some Archaea. 5)then you treat E. coli (a Gram-negative) with lysozyme, you will probably produce A) spheroplast B) peptidoplast C) protoplast D) Thermoplasma E) Mycoplasma 6) Which is NOT true about bacterial cytoplasmic membrane? A) Because it has hydrophilic part, hydrophilic and charged molecules can easily pass through the membranes. B) It is a bilayer of phospholipids. C) Its fluidity can be controlled by changing the length of fatty acids. D) It contains many different kinds of proteins. E) All of the above are true.

Explanation / Answer

1) Penicillin is an effective treatment for gram-positive bacteria infection. Since Staphylococcus aureus is a gram positive bacterium, hence it is sensitive to penicillin treatment. Therefore, your answer is (D). Other options – protoplasts and spheroplasts (by fully or partial removal of bacterial cell wall) are formed after the treatment of penicillin on bacteria while mycoplasma and thermoplasma bacteria are insensitive to penicillin. Hence all these options are not applicable.

2) Penicillin binds its four-membered beta-lactam ring of to DD-transpeptidase, an enzyme that catalyzes the cross-linking of peptidoglycan. This renders the bacterium incapable of biosynthesizing the cell and as a result they die. As we see that none of the given options accurately describes the mechanism of penicillin, therefore, your answer should be (E) i.e. none of the above.

3) Acid fast bacteria like Mycobacterium and Norcadia contain large amounts of lipid substances within their cell walls, called mycolic acids, which resist staining by ordinary methods such as a gram stain. Hence these type of bacteria are stained and identified by Acid-fast stain method. Therefore, your answer is (E). Other options are not applicable to acid-fast bacteria.

4) Pseudopeptidoglycan is a cell wall component of some Archaea only. Other microorganisms- bacteria and rest of the Archaea have peptidoglycan as major component in their cell wall, while eukarya have polysaccharides as the major component in their cell wall. Therefore, your answer is (E).

5) E coli. A gram negative strain when treated with lysozymes or penicillin produces a very fragile cell that is devoid of cell wall. This fully cell wall removed form of bacterial cell is known as protoplast. Therefore, your answer is ( C ). Other options have already been discussed above.

6) The plasma membrane of bacterial cell wall does contain bilayer of phospholipids. The fluidity of plasma membrane can be modulated by bacteria by changing the relative proportion of different fatty acids in the membrane. The cytoplasmic membrane contains various different proteins such as fimbriae and pili, S-layers, etc. It is also true about bacterial cytoplasmic membrane that it allows various hydrophilic and charged molecules to pass through it. Therefore, you see that all the given options refer to cytoplasmic membrane in bacteria and are true, hence you answer should be (E).

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