Cell Structure [2] Flashcards
What is lipid A?
It is the lipid which attaches to the core section of the polysaccharide in a lipid polysaccharide.
Which of the following molecules is shared by both Gram-positive and Gram-negative organisms? A N-acetylmuramic acid B lipopolysaccharide C lipoteichoic acid D lipid A
A
Amoxicillin is an antibiotic that inhibits the formation of peptide cross-links. Amoxicillin, therefore, would most likely inhibit the growth of __________.
A only Gram positive organisms
B neither Gram-positive nor Gram-negative organisms
C both Gram-positive and Gram-negative organisms
D only Gram-negative organisms
C
Porins are present in ______________bacteria because, in these organisms, molecules entering the cell must pass through an extra layer of ___________.
A Gram-positive; membrane
B Gram-negative; membrane
C Gram-positive; peptidoglycan
D Gram-negative; peptidoglycan
E both Gram-negative and Gram-positive; membrane
B
While staining a mixed culture of Gram-positive and Gram-negative bacteria, switching the order of steps 2 and 3 would result in ______________________.
A a change in the Gram reaction; Gram-negative cells would appear purple while Gram-positive cells would appear pink.
B all bacteria appearing pink
C all bacteria appearing clear
D all bacteria appearing purple
B
Axial filaments are found on A staphylococci. B rod-shaped bacilli. C streptococci. D spirochetes.
D
Teichoic acid molecules in Gram-positive cell walls include phosphate groups. Therefore, they will \_\_\_\_\_\_\_\_\_\_. A bind other phosphate ions B bind negative ions like Cl– and SO42– C bind positive ions like Mg2+ and Ca2+ D not bind any ions
C
The presence of which of the components listed below would allow you to distinguish between a gram-positive or gram-negative cell wall? A teichoic acids -- gram-positive B N-acetylmuramic acid – gram-positive C N-acetylglucosamine – gram-negative D teiochic acids -- gram-negative
A
How are negative stains different from other types of stains?
A They stain the desired structure or specimen black.
B They stain the background, leaving the cells colorless.
C They stain more than one type of specimen.
B
What is the fundamental purpose of staining in light microscopy?
A To kill the specimen
B To increase the contrast and visibility of the specimen
C To make the specimen appear larger in the microscope
D To see the specimen without the aid of a microscope
B
Analysis of the second swab has confirmed that the causative organism is Streptococcus pyogenes, a gram-positive organism. Imagine that you are the technician looking at the Gram stain from Shelly’s culture. What would you expect to see as you look through the microscope?
A pink, rod-shaped organisms arranged in pairs
B purple, spherical-shaped organisms arranged in chainlike formations
C purple, spherical-shaped organisms arranged in grapelike clusters
D pink, spherical-shaped organisms arranged in chainlike formations
B
How will the prescribed penicillin kill S. pyogenes that is causing Shelly’s infection?
A Penicillin will attach to bacterial ribosomes and inhibit protein synthesis, which will lead to the death of S. pyogenes.
B Penicillin will interfere with peptidoglycan synthesis, ultimately weakening the cell wall and leading to cellular lysis.
C Penicillin will poke holes in the plasma membrane, weakening the cell and leading to cellular lysis.
D Penicillin will disrupt the outer membrane, leading to a loss of structural integrity and death of S. pyogenes.
B
Predict which type of organism would be more difficult to treat with antibiotics and why.
A gram-negative organisms – thinner peptidoglycan layer
B gram-positive organisms – thicker peptidoglycan layer
C gram-negative organisms – extra layer of LPS
D gram-positive organisms – no LPS laye
C
You have discovered a new coccoid-shaped microorganism with no nucleus, a rigid cell wall, and a diameter of 2 µm. Chemical tests reveal that its cell wall does NOT contain peptidoglycan. The new microorganism is
A most likely an archaeon.
B either a bacterium or an archaeon.
C most likely a eukaryote.
D most likely a bacterium.
A
The lipopolysaccharide (LPS) layer is found ONLY in the cell walls of A Archaea. B gram-negative Bacteria. C gram-positive Bacteria. D Eukarya.
B
An endotoxin is
A a toxin produced in the periplasm of most bacteria.
B the toxic portion of the LPS.
C a toxin known for its primary attack on the epidermis of mammals.
D a toxin produced within archaeal cells.
B
Some of the intestinal symptoms elicited by pathogens such as Salmonella, Shigella, and Escherichia are due to the presence of A S-layers. B peptidoglycan. C lipopolysaccharides. D pseudomurein.
C
