Which of the following observations would suggest that a plate was inoculated with a pure (axenic) culture?

Isolated colonies are all white in color, but some colonies are noticeably larger than others.

Isolated colonies are all white in color and about the same size.

Bacterial growth is apparent in all four quadrants.

Bacterial growth is apparent along the streaks connecting each quadrant.

Isolated colonies are all white in color and about the same size.
Imagine that you forgot to flame the loop before streaking the inoculum from the first quadrant into the second quadrant. What is the most likely consequence of this error?

Too little bacterial growth outside the first quadrant.

Contamination of the Petri plate culture.

Too much bacterial growth outside the first quadrant.

Contamination of the broth culture.

Too much bacterial growth outside the first quadrant.
What is an inoculum?

The inoculating instrument used to transfer bacteria.

The bacteria transferred to a new medium.

The bacteria that are undesired within a culture.

The sterile medium to which bacteria will be transferred.

The bacteria transferred to a new medium.
Which of the following best describes aseptic technique?

To manipulate bacteria without introducing contaminants.

To use chemicals to inhibit or destroy bacteria.

To flame the inoculating loop.

To keep the environment sterile.

To manipulate bacteria without introducing contaminants.
This video shows a student improperly sterilizing an inoculating loop. What is the student’s mistake?

The loop portion of the instrument was heated for too long.

The wire portion of the instrument was not adequately heated.

The loop portion of the instrument was not placed in the correct part of the flame.

The student positioned the hand too close to the flame.

The wire portion of the instrument was not adequately heated.
A student properly flames her loop but then forgets to let it cool. Instead, she immediately inserts the hot loop into her broth culture. What is the most important issue associated with this mistake?

The hot loop may burn the student’s hand.

The hot loop may contaminate the broth culture.

The hot loop may create aerosols when it touches the culture.

The hot loop may distort the bacterial cells.

The hot loop may create aerosols when it touches the culture.
If a student forgets to flame the mouth of a broth culture tube before transferring culture to it, what might result?

The medium will not be warm enough for the culture to grow properly.

Condensation might occur at the top of the tube.

The medium in the tube might become contaminated.

Aerosols might form.

The medium in the tube might become contaminated.
Transfer to an agar deep involves a slightly different procedure from transfer to an agar slant. Which of the following steps is unique to inoculating an agar deep?

The inoculum must be taken from a broth culture.

The agar deep medium must be heated (melted) so that it is liquid when inoculated.

Two loopfuls of inoculum must be transferred.

An inoculating needle is used to stab the inoculum into the agar.

An inoculating needle is used to stab the inoculum into the agar.
The process of transferring microorganisms from one medium to another is known as:

transmission.

planting.

subculturing.

relocation.

subculturing.
Microorganisms are typically present in which of the following locations?

On laboratory surfaces

On your skin

In the air

In the air, on laboratory surfaces, and on your skin

In the air, on laboratory surfaces, and on your skin
When should inoculating instruments be flame sterilized?

Before picking up the inoculum

After transferring the inoculum

Before and after you transfer the culture

You should never sterilize the inoculating instruments using a flame.

Before and after you transfer the culture
Which of the following statements is true regarding proper aseptic culturing techniques?

It is necessary to hold the inoculating instrument in the Bunsen burner flame until it becomes red hot.

After removing the cap of the culture tube, place the cap onto the bench top to prevent contamination.

Blow gently on the sterilized inoculating loop to make sure it is cool enough to pick up the culture.

All of the above

It is necessary to hold the inoculating instrument in the Bunsen burner flame until it becomes red hot.
Once you have sterilized your inoculating loop, it is important that you wait 10-20 seconds before using the loop to pick up a sample from your culture. What is the purpose of letting the inoculating instrument cool off?

Avoid over-heating and damaging the instruments

Ensure that you are taking your time and not rushing the transfer to avoid accidents

Avoid killing the bacterial cells with excess heat

Avoid burning the surface of the bench with the inoculating loop when you place it down on the bench top

Avoid killing the bacterial cells with excess heat
An inoculating _____ is generally used to obtain an inoculum from a broth culture, while an inoculating _____ is typically used to transfer microorganisms to an agar deep tube.

needle; pipette

needle; loop

loop; needle

pipette; loop

loop; needle
Which of the following statements is INCORRECT regarding prokaryotic cells?

They reproduce by binary fission.

They lack a plasma membrane.

They typically have a circular chromosome.

They lack membrane-enclosed organelles.

Their DNA is not enclosed within a membrane.

They lack a plasma membrane.
How do spirochetes and spirilla differ?

Spirilla have an external flagella but spirochetes have axial filaments.

Spirochetes have a rigid, corkscrew shape while spirilla are helical and more flexible.

Spirochetes do not have a cell wall but spirilla do.

Spirochetes and spirilla are basically the same
organisms and the terms can be used interchangeably.

Spirilla are found in chains of cells whereas
spirochetes exist as individual cells.

Spirilla have an external flagella but spirochetes have axial filaments.
The cell walls of bacteria are responsible for the shape of the bacteria and the difference in the Gram stain reaction.

True

False

True
Functions of the glycocalyx include all of the following EXCEPT

biofilm formation.

binary fission.

increased virulence.

source of nutrition.

protection against dehydration.

binary fission.
Which structure acts like an “invisibility cloak” and protects bacteria from being phagocytized?

fimbriae

cell wall

cell membrane

slime layer

capsule

capsule
The difference between simple diffusion and facilitated diffusion is that facilitated diffusion

moves materials from a lower to a higher concentration.

requires transporter proteins.

moves materials from a higher to a lower concentration.

requires ATP.

does not require ATP.

requires transporter proteins.
You have isolated a motile, gram-positive cell with no visible nucleus. You can safely assume that the cell

has 9 pairs + 2 flagella.

lives in an extreme environment.

has cilia.

has a cell wall.

has a mitochondrion.

has a cell wall.
Fimbriae and pili differ in that

pili are used for attachment to surfaces.

pili are used to transfer DNA.

pili are used for motility.

pili are used for transfer of DNA and motility.

there are only one or two pili per cell.

pili are used for transfer of DNA and motility.
Which of the following statements about gram-negative cell walls is FALSE?

Their Gram reaction is due to the outer membrane.

They are toxic to humans.

They are sensitive to penicillin.

They protect the cell in a hypotonic environment.

They have an extra outer layer composed of lipoproteins, lipopolysaccharides, and phospholipids.

They are sensitive to penicillin.
The terms “run” and “tumble” are generally associated with

clustering properties of certain rod-shaped bacteria.

cell wall fluidity.

cell membrane synthesis.

taxic movements of the cell in response to attractants or repellents.

taxic movements of the cell in response to attractants or repellents.
Antibiotics that target the cell wall are an effective treatment against many pathogenic bacteria.

True

False

True
Spheroplasts, protoplasts, and mycoplasms are bacterial cells without cell walls.

True

False

True
If you observe rod-shaped red cells after the Gram stain, you can assume their cell walls contain endotoxin.

True

False

True
Which of the following is NOT a typical characteristic of most bacterial plasma membranes?

contains proteins

composed of a phospholipid bilayer

site of energy production

contains cholesterol

is selectively permeable

contains cholesterol
Which of the following statements best describes what happens when a bacterial cell is placed in a solution containing 5% NaCl?

Water will move out of the cell.

Water will move into the cell.

The cell will undergo osmotic lysis.

Sucrose will move into the cell from a higher to a lower concentration.

No change will result; the solution is isotonic.

Water will move out of the cell.
In bacteria, photosynthetic pigments are found in

chromatophores.

chloroplasts.

mesosomes.

ribosomes.

cytoplasm.

chromatophores.
Which of the following is NOT part of the passive transport process?

plasma membrane

aquaporins

transporter proteins

concentration gradient

ATP

ATP
Which statement regarding the structure or function of ribosomes is correct?

Ribosomes are found both free-floating and attached to the rough endoplasmic reticulum in eukaryotes and in prokaryotes.

Ribosomes are the sites of lipid biosynthesis in both prokaryotes and eukaryotes.

In eukaryotes, the ribosomes found in chloroplasts and mitochondria are 70S ribosomes, which are similar in size to prokaryotic ribosomes.

The ribosomes in the prokaryote are slightly larger than those found in the eukaryotic endoplasmic reticulum.

In eukaryotes, the ribosomes found in chloroplasts and mitochondria are 70S ribosomes, which are similar in size to prokaryotic ribosomes.
Which of the following is found in the cytoplasm of prokaryotic cells but is ABSENT from the cytoplasm of eukaryotic cells?

water

a cytoskeleton

enzymes

DNA

DNA
Which of the following statements accurately describes specific bacterial cell walls?

In bacteria with acid-fast cell walls, the carboxylic acid in the walls forms a layer outside a thin layer of hydrophilic polypeptides.

Gram-negative bacterial cell walls contain teichoic acids, whereas the cell walls of gram-positive bacteria do not.

In gram-negative bacteria, the thin layer of peptidoglycan is surrounded by an outer membrane made of phospholipids, lipopolysaccharides, and proteins.

The cell walls of gram-negative bacteria contain many more layers of peptidoglycan than those of gram-positive bacteria.

In gram-negative bacteria, the thin layer of peptidoglycan is surrounded by an outer membrane made of phospholipids, lipopolysaccharides, and proteins.
You are observing a Gram stain of spherical-shaped microorganisms that are linked in a chain and stain purple. How would you describe these bacteria using the correct terminology for the cell shape and arrangement?

gram-negative staphylococci

gram-positive streptococci

gram-positive coccobacilli

gram-positive tetrads

gram-positive streptococci
Endospores are a reproductive structure.

True

False

False
The DNA found in most bacterial cells

is circular in structure.

is found in multiple copies.

is surrounded by a nuclear membrane.

utilizes histones for chromosomal packaging.

is linear in structure.

is circular in structure.
Which one of the following pairs is mismatched?

sulfur granules – energy reserve

ribosomes – carbon storage

gas vacuoles – flotation

metachromatic granules – phosphate storage

lipid inclusions – energy reserve

ribosomes – carbon storage
Which of the following statements is correct about passive diffusion?

It is a process in which molecules move from a region of lower concentration to one of higher concentration (or up a concentration gradient).

It requires an expenditure of energy by the cell.

It is a process in which molecules move from a region of higher concentration to a region of lower concentration (or down a concentration gradient).

It involves movement of molecules down a concentration gradient and may require a transport protein.

It may require a transport protein.

It involves movement of molecules down a concentration gradient and may require a transport protein.
Where are phospholipids most likely found in a eukaryotic cell?

the plasma membrane

around organelles

ribosomes

surrounding flagella

the plasma membrane, around organelles, and surrounding flagella

the plasma membrane, around organelles, and surrounding flagella
Where are phospholipids most likely found in a prokaryotic cell?

the plasma membrane

flagella

ribosomes

around organelles

the plasma membrane and around organelles

the plasma membrane
Antibiotics that target cell wall synthesis ultimately cause bacterial cell death as a result of

cell shrinkage.

plasmolysis.

inhibition of molecular transport.

osmotic lysis.

decreased synthesis of plasma membrane.

osmotic lysis.
Which of the following statements is TRUE?

A cell can produce many endospores.

Endospores are for reproduction.

Endospores are easily stained in a Gram stain.

Endospores allow a cell to survive environmental changes by producing a dormant period with no growth.

A cell produces one endospore and keeps growing.

Endospores allow a cell to survive environmental changes by producing a dormant period with no growth.
Which of the following organelles most closely resembles a prokaryotic cell?

nucleus

vacuole

mitochondrion

Golgi complex

cell wall

mitochondrion
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