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Which of the following structures is NOT found in all bacteria?


Tumbles occur when

-the flagella rotate clockwise.

Which of the following types of bacterial cells would have only a single flagellum?


Peritrichous bacteria make a run when

-the flagella turn counterclockwise and become bundled.

Which of the following types of bacterial cells would have flagella located at only one end of the cell?

-Lophotrichous and monotrichous

Which of the following statements regarding prokaryotic fimbriae is true?

-Fimbriae may occur either at the poles of a bacterial cell, or can be evenly distributed over the entire surface.

Which of these statements is true regarding plasmids?

-Prokaryotic plasmids may carry genes that provide antibiotic resistance to the cell.

While staining a mixed culture of Gram-positive and Gram-negative bacteria, switching the order of steps 2 and 3 would result in ______________________.

-all bacteria appearing pink

Which structural feature of Gram-positive bacteria enhances their ability to retain the crystal violet dye?

-a thick peptidoglycan layer

What would you anticipate seeing if you accidentally switched crystal violet and safranin while performing a Gram stain?

-All bacteria would appear purple.

What would you expect to see if you forgot to perform step 2 of the Gram stain procedure?

-All bacteria would appear pink.

Which of the following organisms is gram-negative?

-Escherichia coli

Why is it recommended that Gram staining be performed on young bacterial cultures (not older than 24 hours)?

-Over time, gram-positive cells lose their ability to retain the crystal violet stain after decolorization.

What is the most critical step in the Gram staining procedure?

-The decolorization step

If you forgot to add the counterstain to the mixed culture sample at the end of the staining procedure, gram-negative cells would appear __________ and gram-positive cells would appear __________.

-colorless; purple

Which of the following describes the correct cellular morphology and Gram reaction for Staphylococcus aureus?

-Clusters of gram-positive cocci

Which of the following describes the correct cellular morphology and Gram reaction for Bacillus cereus?

-Gram-positive rods

Why is it important that crystal violet be a contrasting color to safranin?

-The contrast allows you to differentiate between gram-negative and gram-positive cells by observing the color of the organism.

Which of the following statements is INCORRECT regarding the Gram staining procedure?

-Gram-negative cells carry a net negative charge in their cell walls; gram-positive cells carry a net positive charge.

Which of the following molecules is shared by both Gram-positive and Gram-negative organisms?

-N-acetylmuramic acid

Amoxicillin is an antibiotic that inhibits the formation of peptide cross-links. Amoxicillin, therefore, would most likely inhibit the growth of __________.

-both Gram-positive and Gram-negative organisms

Porins are present in ______________bacteria because, in these organisms, molecules entering the cell must pass through an extra layer of ___________.

-Gram-negative; membrane

Mycoplasmal pneumonia differs from viral pneumonia in that?

-Mycoplasmal pneumonia is treated with tetracyclines.

Which of the following molecules would be blocked by a cell membrane?


Hydrophobic molecules would enter a cell

-through integral transport proteins.

What is a hallmark of passive transport across cell membranes?

-It occurs along an electrochemical gradient, and may involve the use of transport proteins.

A positively charged sodium ion

-would require the use of integral protein channels to pass through a cell membrane.

Which of the following statements regarding active transport is false?

-It powers the diffusion of water across the cell membrane.

How is osmosis different from simple diffusion?

-Water movement is driven by the concentration of solutes rather than its own concentration.

Nonspecific permeases

-allow a variety of molecules to cross the cytoplasmic membrane.

What will happen to a cell that is placed in a solution containing a high concentration of sugar, a molecule that cannot pass across the cell membrane?

The cell will lose its interior water, causing it to shrivel up and possibly die.

How is simple diffusion different from other types of passive transport?

Simple diffusion does not require a permease.

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