Microbiology Chapter 3

True or false:
In general, bacterial cells are larger than human cells


True or false:
Bacteria are only visible when using an electron microscope


What is the term used to describe a cluster of spherical bacteria?


What general type of staining is used to separate various types of bacteria based on their cellular structures?


Why must fresh cells be used for the Gram stain?

As cells age, they may not stain correctly

If you viewed the slide microscopically after the crystal violet step, Gram-positive cells would appear ______ in color while Gram-negative cells would appear ______ in color.

Purple; purple

Why is Gram's iodine added to the slide?

It forms complexes with the crystal violet, decreasing its solubility

If you viewed the slide microscopically after the ethanol/acetone step, Gram-positive cells would appear ______, while Gram-negative cells would appear ______.

Purple; colorless

Gram-positive bacteria retain the crystal violet-iodine complexes because the ethanol/acetone

shrinks the thick peptidoglycan cell wall, making it impermeable

During the Gram stain procedure, bacteria can first be differentiated from each other after the application of ______.

Ethanol or acetone

If the Gram's iodine step was skipped in this technique, what would likely be seen under the microscope, providing all other steps were performed correctly?

Most cells would appear red/pink

True or false:
All bacteria can be classified as either Gram-positive or Gram-negative.


True or false:
The presence of flagella can be determined by a Gram stain.


Rod-shaped bacteria can be?

Either Gram-positive or Gram-negative

After Gram's iodine is added to the slide, what color do cells appear?

All cells appear purple in color

True or false:
The thinner peptidoglycan layer of Gram-positive bacteria allows the crystal violet-iodine complex to leave the cell.


Which of the following cell arrangements is described CORRECTLY?
A. Diplobacillus - pairs of spherical cells
B. Staphylococcus - chains of spherical cells
C. Streptococcus - grape-like clusters of spherical cells
D. Streptobacillus - grape-like clusters o


True or false:
Mycoplasma pneumoniae lacks a cell wall and has a pleomorphic morphology.


Which of the following bacterial groups is described CORRECTLY?
A. Spirochetes - move by axial fibrils.
B. Actinomycetes - reproduce by fragmentation.
C. Nocardiae - form specialized dispersal cells on aerial mycelia.
D. Spirochetes - move by axial fibril


Which of the following bacterial genera is NOT described correctly?
A. Clostridium - spore-forming rod
B. Corynebacterium - spherical
C. Vibrio - curved rod
D. Clostridium - spore-forming rod and
Vibrio - curved rod
E. Clostridium - spore-forming rod and


Which of the following can affect the resolution of a bright-field microscope?
A. Wavelength of light
B. Type of specimen
C. Quality of lenses
D. Magnification
E. Type of specimen AND magnification

A, B, C


Ability to distinguish between an object and its surroundings


Ability to distinguish between two points or objects that are very close to one another

Which differential staining method is most important in the diagnosis of tuberculosis?
A. Endospore staining
B. Gram stain
C. Flagella stain
D. Acid-fast stain


Which of the following dyes is used first in an acid-fast stain?
A. Methylene blue
B. Safranin
C. Carbol fuchsin
D. Crystal violet
E. Malachite green


In the Gram-positive bacterial cell wall, the polymers of NAM and NAG sugars in peptidoglycan are cross-linked together by tetrapeptide chains and ______.

Peptide interbridges

Component of the outer membrane in Gram-negative bacteria that, in large amounts, can induce a lethal immunological response?


True or false:
Small amounts of LPS alert the body to invasion by Gram-negative bacteria, while large amounts of LPS may cause shock and death.


Lipid A

- Anchors LPS in outer membrane
- Alerts immune system to Gram-negative bacteria
- Composed mostly of fatty acids
- Causes endotoxic effects

O Antigen

- Composed of polysaccharides
- Used to identify bacterial strains
- Outermost part of LPS

The target of penicillin in bacterial cells is ______.

The cell wall

The target of lysozyme in bacterial cells is the ______.

The cell wall


- Distinct edges
- Gelatinous (fairly solid)

Slime layer

- Irregular edges
- Diffuse (less solid)

If you remove the glycocalyx of a bacterium, the organism would no longer be able to

Attach to surfaces

Sex pilus

Responsible for transferring DNA from one bacterial cell to another


Responsible for locomotion


Responsible for bacterial attachment to surfaces


Involved in cell division and controlling cell shape


Involved in protein synthesis


Contains genetic information required for survival

Gas vesicle

Contains compounds that aid in buoyancy


A dormant cell state

Storage granules

Contains high-molecular weight polymers


Typically contains genetic information that is not required by the cell

Triggers sporulation for bacteria

Nutrient depletion

During phagocytosis, cellular membrane projections will "wrap around" a target. What are these cellular projections called?



Location for the cellular process of photosynthesis.


Location for storage of many types of degradative enzymes.

Golgi Apparatus

Location for protein modification prior to secretion or delivery to other cellular compartments.


Location for storage of protective compounds that break down lipids and detoxify certain chemicals.


Location for DNA, and for RNA synthesis.

Endoplasmic Reticulum

Location for protein synthesis and some protein modifications.


Location for most metabolic reactions in cellular respiration.

A eukaryotic cell that is involved in synthesizing large amounts of protein might be expected to have

- Many ribosomes
- Many chloroplasts
- A lot of smooth ER

Found exclusively in eukaryotic cells

- Lysosomes
- Golgi Apparatus
- Mitochondria
- Endoplasmic Reticulum

Found exclusively in prokaryotic cells

- Endospore

Gram positive

- Purple
- Lots of peptidoglycan

Gram negative

- Pink
- Not much peptidoglycan
- Protective outer membrane

Prokaryotic cells

- Small
- Simple
- Unicellular
- No true nucleus
- One circular chromosome
- No membrane enclosed organelles
- 70S ribosomes

Eukaryotic cells

- True nucleus
- Larger
- Complex
- Unicellular OR multicellular
- Many linear chromosomes
- Contains membrane enclosed organelles
- 80S ribosomes


A spherical bacterium


Cylindrical shape bacterium


Curved rod/Comma shape bacterium


A spiral-shaped bacterium


A spiral-shaped bacterium

Most prokaryotic/bacteria divide by?

Binary fission

Cell envelope

Everything that surrounds the inner cell cytosol

Cytoplasmic membrane

A semipermeable barrier that separates the cell interior (cytoplasm) from the environment

True or false:
All cells have a cell membrane


Cell wall

- Made up of peptidoglycan
- Peptides and sugar

Gram positive cell wall

- Many layers of peptidoglycan
- Teichoic acid

Gram negative cell wall

- Thin peptidoglycan layer
- Outer and inner membrane
- Space between membranes contains a thin peptidoglycan cell wall
- Outer membrane contains lipopolysaccharides & porin proteins