Question 1

Hydrolytic enzymes function in the
A) initial degradation of nutrients.
B) transport of substrates within the cell.
C) chemotactic response, particularly in gram-negative Bacteria.
D) regeneration of the periplasm.

Accepted Answer

Hydrolytic enzymes are responsible for breaking down large molecules, such as nutrients, into smaller, more easily absorbed molecules in the initial stages of degradation.

Answer: D 
 Hydrolytic enzymes can also function in the process of regenerating the periplasm, which is the space between the inner and outer membranes of Gram-negative bacteria. Within the periplasm, these enzymes can break down macromolecules to supply nutrients to the cell.

Therefore, the best choices are A and D.

Question 2

The terms "run" and "tumble" are generally associated with
A) eukaryotic cells.
B) nutrient transport.
C) chemotaxis.
D) clustering of certain rod-shaped bacteria.

Accepted Answer

The terms "run" and "tumble" are commonly used to describe the movement of bacteria during chemotaxis, which is the process by which bacteria move towards or away from chemical stimuli in their environment. When the bacteria sense a gradient of attractant molecules, they exhibit a "run" behavior where they move in a straight line towards the source. If the bacteria sense a gradient of repellent molecules or if they lose the gradient of attractant, they exhibit a "tumble" behavior where they change their direction randomly. This allows the bacteria to explore their environment and find the optimal conditions for survival.

Question 3

Some archaea have unique phospholipids in their cytoplasmic membrane that
A) form a monolayer due to the presence of diglycerol tetraethers.
B) form a bilayer due to the presence of sterols.
C) form a stable ring structure due to the presence of crenarchaeol.
D) form a bilayer due to the presence of phosphatidylethanolamine.

Accepted Answer

Archaea membrane lipids differ from those of bacteria and eukaryotes in several ways, including the presence of isoprenoid chains, ether linkages between glycerol and fatty acids, and lack of fatty acid unsaturation. Some archaea also have unique phospholipids in their cytoplasmic membrane that form a monolayer due to the presence of diglycerol tetraethers, such as in the case of thermophilic bacteria. This structure provides stability and resistance to heat, which is an advantage in extreme environments.

Question 4

The cytoplasmic membrane could best be described as
A) an impermeable barrier.
B) a passive conduit for intracellular transport.
C) a highly selective permeability barrier.
D) a rigid structure that protects the cell.

Accepted Answer

The cytoplasmic membrane is a highly selective permeability barrier that only allows specific molecules to pass through while preventing the entrance of others. It regulates the movement of ions and nutrients into and out of the cell, maintains the cell's shape and integrity, and plays a crucial role in cellular communication and signaling.

Question 5

Bacteria stain as gram-positive or gram-negative because of differences in the cell
A) wall.
B) cytoplasm.
C) nucleus.
D) chromosome.

Accepted Answer

Gram-positive and Gram-negative bacteria have differences in the composition and structure of their cell walls, which affects the ability of the bacteria to retain or lose the crystal violet stain during the Gram staining process. Gram-positive bacteria have a thick peptidoglycan layer in their cell walls that can retain the crystal violet stain, while Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane that can cause them to lose the stain. The composition and structure of the cytoplasm, nucleus, and chromosome do not play a direct role in the Gram staining process.

Question 6

The cell wall of a Gram-positive bacterium is composed of a thick ________ layer.
A) protein
B) poly-β-hydroxybutryic acid (PHB)
C) lipopolysaccharides (LPS)
D) peptidoglycan

Accepted Answer

The cell wall of Gram-positive bacteria is composed of a thick layer of peptidoglycan, whereas Gram-negative bacteria have a thinner layer of peptidoglycan surrounded by an outer membrane containing lipopolysaccharides. Choice A (protein) and B (poly-β-hydroxybutryic acid) are not components of the Gram-positive cell wall, and Choice C (lipopolysaccharides) is a component of the Gram-negative cell wall, not the Gram-positive cell wall.

Question 7

Transport proteins located in the cytoplasmic membrane are necessary when
A) diffusion will not allow adequate amounts of a substance to enter the cell.
B) movement into the cell is against a concentration gradient.
C) the level of nutrients in nature is very low.
D) nutrient concentration is very low in the environment, is higher inside of the cell, or diffusion is not possible.

Accepted Answer

Transport proteins located in the cytoplasmic membrane are necessary when nutrient concentration is very low in the environment, is higher inside of the cell, or diffusion is not possible. These proteins aid in the movement of substances into the cell against the concentration gradient, ensuring adequate levels of nutrients within the cell.

Question 8

An organism of the genus Staphylococcus is ________, while an organism of the genus Spirochaeta is ________.
A) spherical / rod shaped
B) rod shaped / coiled
C) spherical / coiled
D) coiled / spherical

Accepted Answer

Organisms of the genus Staphylococcus are spherical (cocci), while organisms of the genus Spirochaeta are coiled, reflecting their spiral shape.

Question 9

Compared to Eukaryotes, Bacteria and Archaea have ________ surface-to-volume ratios, causing ________ nutrient exchange.
A) lower / lower
B) lower / higher
C) higher / lower
D) higher / higher

Accepted Answer

Bacteria and Archaea, being generally smaller than eukaryotic cells, have higher surface-to-volume ratios, which facilitates higher rates of nutrient exchange due to more surface area relative to their volume.

Question 10

Using phase contrast microscopy on a wet mount of live cells, you observe motile bacilli moving rapidly and randomly through the field of view, changing directions after a brief tumble and taking off in a different direction. These cells are exhibiting ________ motility.
A) twitching
B) swimming
C) gliding
D) twitching or gliding

Accepted Answer

The rapid and random movement of the motile bacilli followed by tumbling and changing direction is characteristic of swimming motility. Twitching and gliding motility involve different mechanisms of movement and are not consistent with the observed behavior.

Question 11

You are given an electron micrograph of a bacterial cell. In the micrograph you can clearly see three thin layers of different densities surrounding the cell. Based on the micrograph, you can infer that this cell is ________ and would appear ________ after application of the Gram stain procedure.
A) gram-positive / purple
B) gram-negative / pink
C) gram-positive / pink
D) gram-negative / purple

Accepted Answer

The presence of three thin layers of different densities surrounding the cell indicates that it is a gram-negative bacterium. The Gram stain procedure involves applying crystal violet, iodine, alcohol, and safranin to the bacterial cells, which allows gram-positive cells to retain the violet color and appear purple under the microscope, while gram-negative cells lose the violet color and appear pink after the addition of safranin.

Question 12

An endotoxin is
A) the toxic portion of the LPS.
B) a toxin produced within archaeal cells.
C) a toxin known for its primary attack on the epidermis of mammals.
D) a toxin produced in the periplasm of most bacteria.

Accepted Answer

Endotoxins are the toxic portion of lipopolysaccharides (LPS), which are found in the outer membranes of gram-negative bacteria. When the bacterial cell is lysed, the LPS is released, causing an inflammatory response in the host organism.

Question 13

The lipopolysaccharide (LPS) layer is found ONLY in the cell walls of
A) gram-positive Bacteria.
B) gram-negative Bacteria.
C) Archaea.
D) Eukarya.

Accepted Answer

The LPS layer, also known as endotoxin, is a major component of the cell wall of gram-negative Bacteria. The layer consists of lipids and polysaccharides, and plays a role in various functions such as protecting against host immune responses and regulating permeability. Gram-positive Bacteria do not have an LPS layer, but instead have a thick peptidoglycan layer in their cell wall. Archaea and Eukarya have different types of cell membranes and cell walls not containing LPS.

Question 14

The use of the Gram stain in microbiology is important because it differentiates
A) Bacteria from Archaea.
B) prokaryotic from eukaryotic cells.
C) bacterial cells with different types of cell walls.
D) archaeal cells with different types of metabolism.

Accepted Answer

The Gram stain differentiates bacterial cells with different types of cell walls. The cell walls of Gram-negative bacteria have a thin layer of peptidoglycan surrounded by an outer membrane, while the cell walls of Gram-positive bacteria have a thick layer of peptidoglycan. The stain allows for differentiation between these two types of bacteria. It does not differentiate between Bacteria and Archaea or prokaryotic and eukaryotic cells, nor does it distinguish between archaeal cells with different types of metabolism.

Question 15

Which of the following statements is FALSE?
A) A flagellar protein subunit is flagellin.
B) In flagellar motion, the basal body acts as a motor.
C) Flagellar rotation generates ATP.
D) The hook is the wider region at the base of the flagellum.

Accepted Answer

Flagellar rotation utilizes energy from the proton motive force or the flow of ions, not ATP synthesis.

Question 16

The morphology of a cell influences its
A) motility.
B) metabolism.
C) surface-to-volume ratio.
D) motility and surface-to-volume ratio.

Accepted Answer

The morphology of a cell influences both its motility, as the shape can affect how it moves, and its surface-to-volume ratio, which impacts how substances can enter or leave the cell.

Question 17

Cells move polar molecules across the cell membrane against a concentration gradient using
A) energy and transport proteins.
B) simple diffusion.
C) modifications to membrane lipids.
D) random molecular movement.

Accepted Answer

Polar molecules cannot diffuse easily across the cell membrane, and therefore require transport proteins for facilitated diffusion or active transport. Active transport requires the input of energy, which is typically in the form of ATP, to move molecules against a concentration gradient.

Question 18

You have discovered a new microorganism and would like to classify it as a eukaryote or a prokaryote. To investigate this question you prepare a slide with a simple stain and view it with a light microscope with a 40X objective lens and 10X ocular lens. You also prepare a control slide using Saccharomyces cerevisiae (a unicellular eukaryote). You can see the cells on your control slide, but you don't see cells when you look at your unknown microorganism. What can you conclude from this experiment?
A) The experiment failed to visualize the organism because the stain killed it.
B) Your new unknown microorganism is probably a virus.
C) The cells of the new unknown microorganism may be too small to see with the objective and ocular lenses you used.
D) The new unknown microorganism is probably an archaeon.

Accepted Answer

The fact that cells were not seen with the microscope suggests that they may be too small to be observed using the lenses and staining method used. This does not provide evidence for it being a virus or an archaeon. Additionally, the control slide of Saccharomyces cerevisiae confirms that the staining protocol and microscopic setup was effective in visualizing eukaryotic cells, and therefore increases the likelihood that the unknown microorganism is a prokaryote.

Question 19

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 a bacterium.
B) most likely a eukaryote.
C) most likely an archaeon.
D) either a bacterium or an archaeon.

Accepted Answer

The lack of peptidoglycan in the cell wall suggests that this microorganism is not a bacterium. Instead, it could be an archaeon or a eukaryote. However, the presence of a rigid cell wall and the absence of a nucleus suggest that it is more likely to be an archaeon.

Question 20

Bacteria with type IV pili
A) possess tubular or stalk-like extensions of their cells.
B) likely exhibit twitching motility.
C) have capsules that promote dehydration.
D) live in aquatic environments.

Accepted Answer

Type IV pili are involved in a form of movement known as twitching motility, which allows bacteria to move across surfaces.

Quiz 2: Microbial Cell Structure and Function

Hydrolytic enzymes function in the

The terms "run" and "tumble" are generally associated with

Some archaea have unique phospholipids in their cytoplasmic membrane that

The cytoplasmic membrane could best be described as

Bacteria stain as gram-positive or gram-negative because of differences in the cell

The cell wall of a Gram-positive bacterium is composed of a thick ________ layer.

Transport proteins located in the cytoplasmic membrane are necessary when

An organism of the genus Staphylococcus is , while an organism of the genus Spirochaeta is .

Compared to Eukaryotes, Bacteria and Archaea have surface-to-volume ratios, causing nutrient exchange.

Using phase contrast microscopy on a wet mount of live cells, you observe motile bacilli moving rapidly and randomly through the field of view, changing directions after a brief tumble and taking off in a different direction. These cells are exhibiting ________ motility.

You are given an electron micrograph of a bacterial cell. In the micrograph you can clearly see three thin layers of different densities surrounding the cell. Based on the micrograph, you can infer that this cell is and would appear after application of the Gram stain procedure.

An endotoxin is

The lipopolysaccharide (LPS) layer is found ONLY in the cell walls of

The use of the Gram stain in microbiology is important because it differentiates

Which of the following statements is FALSE?

The morphology of a cell influences its

Cells move polar molecules across the cell membrane against a concentration gradient using

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

Bacteria with type IV pili