Get your research papers, homework and online exams done from just $8 per page

We also have verified textbook solutions at just $3 per answer; No subscription needed

Do my Homework

C H A P T E R 2 Structure of Bacterial Cells

Category:
« Back to Previous Page
▲
0
▼
♥ 0
  1. The initial step in the process of many bacterial infections is

adherence of the organism to mucous membranes. The bacterial

component that mediates adherence is the:

(A) lipid A

(B) nucleoid

(C) peptidoglycan

(D) pilus

(E) plasmid

 

  1. In the Gram stain procedure, bacteria are exposed to 95% alcohol

or to an acetone/alcohol mixture. The purpose of this step is:

(A) to adhere the cells to the slide

(B) to retain the purple dye within all the bacteria

(C) to disrupt the outer cell membrane so the purple dye can

leave the bacteria

(D) to facilitate the entry of the purple dye into the gram-negative

cells

(E) to form a complex with the iodine solution

 

  1. In the process of studying how bacteria cause disease, it was

found that a rare mutant of a pathogenic strain failed to form

a capsule. Which one of the following statements is the most

accurate in regard to this unencapsulated mutant strain?

(A) It was nonpathogenic primarily because it was easily

phagocytized.

(B) It was nonpathogenic primarily because it could not invade

tissue.

(C) It was nonpathogenic primarily because it could only grow

anaerobically.

(D) It was highly pathogenic because it could secrete larger

amounts of exotoxin.

(E) It was highly pathogenic because it could secrete larger

amounts of endotoxin.

 

  1. Mycobacterium tuberculosis stains well with the acid-fast stain,

but not with the Gram stain. Which one of the following is the

most likely reason for this observation?

(A) It has a large number of pili that absorb the purple dye.

(B) It has a large amount of lipid that prevents entry of the purple

dye.

(C) It has a very thin cell wall that does not retain the purple

dye.

(D) It is too thin to be seen in the Gram stain.

(E) It has histones that are highly negatively charged.

 

  1. Of the following bacterial components, which one exhibits the

most antigenic variation?

(A) Capsule

(B) Lipid A of endotoxin

(C) Peptidoglycan

(D) Ribosome

(E) Spore

 

  1. Lactamases are an important cause of antibiotic resistance.

Which one of the following is the most common site where

-lactamases are located?

(A) Attached to DNA in the nucleoid

(B) Attached to pili on the bacterial surface

(C) Free in the cytoplasm

(D) Within the capsule

(E) Within the periplasmic space

 

  1. Which one of the following is the most accurate description of

the structural differences between gram-positive bacteria and

gram-negative bacteria?

(A) Gram-positive bacteria have a thick peptidoglycan layer,

whereas gram-negative bacteria have a thin layer.

(B) Gram-positive bacteria have an outer lipid-rich membrane,

whereas gram-negative bacteria do not.

(C) Gram-positive bacteria form a sex pilus that mediates conjugation,

whereas gram-negative bacteria do not.

(D) Gram-positive bacteria have plasmids, whereas gram-negative

bacteria do not.

(E) Gram-positive bacteria have capsules, whereas gram-negative

bacteria do not.

 

  1. Bacteria that cause nosocomial (hospital-acquired) infections

often produce extracellular substances that allow them to stick

firmly to medical devices, such as intravenous catheters. Which

one of the following is the name of this extracellular substance?

(A) Axial filament

(B) Endotoxin

(C) Flagella

(D) Glycocalyx

(E) Porin

 

  1. Lysozyme in tears is an effective mechanism for preventing bacterial

conjunctivitis. Which one of the following bacterial structures

does lysozyme degrade?

(A) Endotoxin

(B) Nucleoid DNA

(C) Peptidoglycan

(D) Pilus

(E) Plasmid DNA

 

  1. Several bacteria that form spores are important human pathogens.

Which one of the following is the most accurate statement

about bacterial spores?

(A) They are killed by boiling for 15 minutes.

(B) They are produced primarily by gram-negative cocci.

(C) They are formed primarily when the bacterium is exposed to

antibiotics.

(D) They are produced by anaerobes only in the presence of oxygen.

(E) They are metabolically inactive yet can survive for years in

that inactive state.

✅ Answers (1)

▲
0
▼
✔
Private answer

(1) (D)

(D) pilus

A pilus is a thin, rigid fiber made of protein that protrudes from the cell surface. The primary function of pili are to attach a bacterial cell to specific surfaces or to other cells.

 

(2) (C)

(C) to disrupt the outer cell membrane so the purple dye can

leave the bacteria

After staining the sample with crystal violet, ethyl alcohol is used to decolorize the sample. It achieves its purpose by dehydrating the peptidoglycan layer by tightening and shrinking it.

 

(3) (A)

(A) It was nonpathogenic primarily because it was easily

phagocytized.

Nonpathogenic organisms are those that do not cause disease, harm or death to another organism and is usually used to describe bacteria. It describes a property of a bacterium - its ability to cause disease. Most bacteria are nonpathogenic

 

(4) (B)

(B) It has a large amount of lipid that prevents entry of the purple

dye.

Gram staining is based on the ability of bacteria cell wall to retaining the crystal violet dye during solvent treatment. The cell walls for Gram-positive microorganisms have a higher peptidoglycan and lower lipid content than gram-negative bacteria. Bacteria cell walls are stained by the crystal violet.

 

(5) (A)

(A) Capsule

Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response. It is related to phase variation.

 

(6) (E)

(E) Within the periplasmic space

β-Lactamases are enzymes that degrade the β-lactam ring. They can be encoded chromosomally or on extrachromosomal elements. In GPOs, they are excreted into the extracellular space, whereas in GNOs they are found in the periplasmic space.

 

(7) (A)

(A) Gram-positive bacteria have a thick peptidoglycan layer,

whereas gram-negative bacteria have a thin layer.

Gram-negative bacteria are surrounded by a thin peptidoglycan cell wall, which itself is surrounded by an outer membrane containing lipopolysaccharide. Gram-positive bacteria lack an outer membrane but are surrounded by layers of peptidoglycan many times thicker than is found in the Gram-negatives.

 

(8) (D)

(D) Glycocalyx

This coating of macromolecules protects the cell and helps it adhere to surfaces. A glycocalyx is considered a slime layer when the glycoprotein molecules are loosely associated with the cell wall. Bacteria that are covered with this loose shield are protected from dehydration and loss of nutrients.

 

(9) (C)

(C) Peptidoglycan

Lysozyme degrades peptidoglycan in the bacterial cell wall leading to rapid killing of Gram-positive organisms; however, this mechanism cannot account for the protective effect of lysozyme against Gram-negative bacteria.

 

(10) (E)

(E) They are metabolically inactive yet can survive for years in

that inactive state.

To survive periods of adverse conditions many bacteria switch to a metabolically inactive, dormant state. One of the best-studied types of dormancy is sporulation. Spores are physiologically distinct from vegetative cells; they are highly resistant to stresses, such as antibiotics and heat, and can survive for years in wait for better times. Once growth-permissive conditions return, the spores germinate and reinitiate growth

 

 

Marked as spam
Answered on June 24, 2020 5:04 pm
« Back to Previous Page

Professional Essay Helpers Online

Get your papers written by online essay writers available 24/7. Submit your assignments and get a quality plagiarism-free paper via email.

Write My Paper For Me