Question 1

During the Gram stain,_____ cells decolorize when the alcohol is applied.

Accepted Answer

Gram-negative cells decolorize when the alcohol is applied to them during the Gram stain, while gram-positive cells retain the crystal violet stain. Therefore, the correct choice is B, gram-negative. Choice C is incorrect since gram-positive cells do not decolorize during the alcohol application step.

Question 2

Movement of a cell toward a chemical stimulus is termed

Accepted Answer

Chemotaxis refers to the directed movement of cells in response to a chemical stimulus. Positive chemotaxis means the cell is moving towards the chemical stimulus, whereas negative chemotaxis means it is moving away from it. Phototaxis refers specifically to movement in response to light, not chemical stimuli. A tumble is a type of movement in bacteria that involves a random change in direction.

Question 3

The short,numerous appendages used by some bacterial cells for adhering to surfaces are called

Accepted Answer

Fimbriae, also known as pili, are short, numerous appendages used by some bacterial cells for adherence to surfaces. They are typically shorter and more numerous than flagella, which are used for motility. Cilia are not present in bacteria, and periplasmic flagella/axial filaments are only present in certain bacterial species. Sex pili are similar to fimbriae, but are used for bacterial conjugation rather than adherence to surfaces.

Question 4

The term that refers to flagella at both poles is

Accepted Answer

Amphitrichous refers to flagella at both poles. Lophotrichous refers to multiple flagella at one or both poles, monotrichous refers to a single flagellum at one pole, peritrichous refers to flagella distributed all over the surface of the cell, and atrichous refers to the absence of flagella.

Question 5

A bacterial cell exhibiting chemotaxis probably has

Accepted Answer

Chemotaxis refers to the movement of a cell in response to a chemical gradient, and bacterial flagella are responsible for bacterial motility and directionality in response to chemical signals.

Question 6

The bacterial flagellum has three parts in the order from cytoplasm to external environment:

Accepted Answer

The bacterial flagellum is composed of three main parts: the basal body, which anchors the flagellum to the cell membrane and acts as a motor; the hook, which connects the basal body to the filament; and the filament, which extends into the external environment and is responsible for propulsion.

Question 7

If bacteria living in salty seawater were displaced to a freshwater environment,the cell structure that would prevent the cells from rupturing is the

Accepted Answer

The cell wall provides rigidity and structural support to bacterial cells, preventing them from bursting in hypotonic (less salty) environments. Therefore, the cell wall would be the structure that prevents bacteria from rupturing in freshwater environments. The other structures listed do not necessarily provide the same level of protection against osmotic pressure changes.

Question 8

The two functions of bacterial appendages are

Accepted Answer

Bacterial appendages serve two main functions: attachment and motility. Examples of attachment structures include pili and fimbriae, which help bacteria attach to surfaces or host cells. Flagella are examples of motility structures that allow bacteria to move through their environment. Therefore, option B is the best choice.

Question 9

Which of the following is not a characteristic of bacteria?

Accepted Answer

Bacteria do not have DNA wrapped around histones like eukaryotic cells do.

Question 10

Chemotaxis refers to the ability to

Accepted Answer

Chemotaxis specifically refers to the movement of an organism or cell in response to a chemical stimulus.

Question 11

The cell _____ can be composed of three layers: the cytoplasmic membrane,the cell wall,and the outer membrane.

Accepted Answer

The term "envelope" is commonly used to describe the outermost boundary of certain types of cells, particularly bacterial cells. This envelope can consist of three layers: the cytoplasmic membrane (also known as the plasma membrane), the cell wall, and an outer membrane (in some gram-negative bacteria). The envelope helps to protect the cell from its environment and maintain its shape.

Question 12

The transfer of genes during bacterial conjugation involves rigid,tubular appendages called

Accepted Answer

The transfer of genes during bacterial conjugation involves sex pili, which are rigid, tubular appendages that are used to connect two bacterial cells and transfer genetic material between them. Flagella are not involved in conjugation, but are used for motility. Cilia are not found in bacteria. Fimbriae are shorter, hair-like appendages used for adherence to surfaces. Periplasmic flagella are found in spirochetes and are used for movement.

Question 13

The term that refers to the presence of flagella over the cell surface is

Accepted Answer

The term that refers to the presence of flagella distributed all over the surface of the cell is peritrichous. A - Amphitrichous flagella are present at both ends of the cell. B - Atrichous cells do not have any flagella. C - Lophotrichous cells have a cluster of flagella at one or both ends. D - Monotrichous cells have a single flagellum at one end.

Question 14

The term that refers to the presence of a tuft of flagella emerging from the same site is

Accepted Answer

The term "lophotrichous" refers to the presence of a tuft of flagella emerging from the same site. "Amphitrichous" refers to flagella at both ends of a bacterium, "atrichous" refers to the absence of flagella, "monotrichous" refers to a single flagellum at one end of a bacterium, and "peritrichous" refers to flagella distributed over the entire surface of a bacterium.

Question 15

The outcome of the Gram stain is based on differences in the cell's

Accepted Answer

The Gram stain is used to differentiate bacterial species based on the characteristics of their cell walls. Gram-positive bacteria have a thick peptidoglycan layer in their cell walls, which retains the crystal violet stain used in the Gram stain. Gram-negative bacteria have a thinner peptidoglycan layer and an additional outer membrane that prevents retention of the crystal violet stain, instead taking up the counterstain safranin. The difference in the cell wall composition determines the outcome of the Gram stain, making choice C the correct answer.

Question 16

Which structure protects bacteria from being phagocytized by white blood cells?

Accepted Answer

The capsule is a thick, well-defined layer outside the cell wall that protects bacteria from being phagocytized by white blood cells. The capsule makes it difficult for the immune system to recognize bacteria and attack them, thus protecting them from being engulfed by phagocytic cells. The other choices may have a protective function, but the capsule is the most effective at preventing phagocytosis.

Question 17

Spirochetes have a twisting and flexing locomotion due to appendages called

Accepted Answer

Spirochetes have specialized appendages called periplasmic flagella or axial filaments that allow them to twist and flex in a corkscrew-like motion. These flagella are located between the outer membrane and the cytoplasmic membrane and are responsible for the unique motility of spirochetes. Option A is incorrect because regular flagella are rigid and do not allow for the twisting and flexing motion of spirochetes. Options B, C, and E are also incorrect as they refer to different types of appendages that are not present in spirochetes.

Question 18

A flagellum is anchored into the bacterial cell envelope by its

Accepted Answer

The basal body anchors the flagellum into the bacterial cell envelope. The hook, filament, and sheath are all parts of the flagellum itself. The outer membrane is only present in Gram-negative bacteria and is not directly involved in anchoring the flagellum.

Question 19

Bacterial cells could have any of the following appendages except

Accepted Answer

Bacteria do not have cilia. Cilia are a characteristic feature of eukaryotic cells, such as those found in animals and some protists.

Question 20

Which order below reflects the correct procedure for Gram staining?

Accepted Answer

The correct procedure for Gram staining is: 
1. Crystal violet: to stain all cells 
2. Iodine: to form a crystal violet-iodine complex that locks the dye inside the cells 
3. Alcohol/acetone: to remove the dye from Gram-negative cells (decolorization) 
4. Safranin: to stain Gram-negative cells with a different color than Gram-positive cells 
Therefore, the correct order is crystal violet-iodine-alcohol/acetone-safranin, which matches option C.

Quiz 3: Bacteria and Archaea