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Ch. 4 - Functional Anatomy of Prokaryotic and Eukaryotic Cells
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
All textbooksTortora 14th EditionCh. 4 - Functional Anatomy of Prokaryotic and Eukaryotic CellsProblem 10
Chapter 4, Problem 10

The antibiotic amphotericin B disrupts plasma membranes by combining with sterols; it will affect all of the following cells except
a. Animal cells.
b. Gram-negative bacterial cells.
c. Fungal cells.
d. Mycoplasma cells.
e. Plant cells.

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1
Understand the mechanism of action of amphotericin B: it binds to sterols in plasma membranes, disrupting membrane integrity and causing cell death.
Identify which types of cells contain sterols in their plasma membranes. Typically, animal, fungal, and plant cells have sterols such as cholesterol or ergosterol in their membranes.
Recognize that most bacterial cells, including gram-negative bacteria, do not have sterols in their plasma membranes, with the exception of Mycoplasma species, which do contain sterols.
Analyze each option: animal cells (have sterols), fungal cells (have ergosterol), plant cells (have sterols), Mycoplasma cells (have sterols), and gram-negative bacterial cells (generally lack sterols).
Conclude that amphotericin B will not affect cells lacking sterols, so the correct answer is the cell type without sterols in its membrane.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mechanism of Action of Amphotericin B

Amphotericin B is an antifungal antibiotic that binds to sterols, primarily ergosterol, in cell membranes. This binding disrupts membrane integrity, causing leakage of cellular contents and cell death. Its specificity depends on the presence of sterols in the target cell membrane.
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Sterol Composition in Different Cell Types

Sterols like cholesterol and ergosterol are essential components of eukaryotic cell membranes. Fungal cells contain ergosterol, animal and plant cells contain cholesterol and phytosterols respectively, while most bacterial cells, including gram-negative bacteria, lack sterols in their membranes.
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Unique Characteristics of Mycoplasma Cell Membranes

Mycoplasma are bacteria that lack a cell wall but incorporate sterols from their environment into their plasma membranes. This sterol presence makes them unique among bacteria and influences their susceptibility to membrane-targeting agents like amphotericin B.
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Related Practice
Textbook Question

You have isolated a motile, gram-positive cell with no visible nucleus. You can assume this cell has

a. Ribosomes.

b. Mitochondria.

c. An endoplasmic reticulum.

d. A Golgi complex.

e. All of the above

Textbook Question

Starch is readily metabolized by many cells, but a starch molecule is too large to cross the plasma membrane. How does a cell obtain the glucose molecules from a starch polymer? How does the cell transport these glucose molecules across the plasma membrane?

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Textbook Question

Use the following choices to answer questions 3–5:

a. Bacillus coagulans

b. Byssochlamys

c. flat sour spoilage

d. Lactobacillus

e. thermophilic anaerobic spoilage


A heat-resistant fungus that causes spoilage in acidic foods.

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Textbook Question

Match the characteristics of eukaryotic cells in column A with their functions in column B.

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Textbook Question

What group of microbes is characterized by cells that form filaments, reproduce by spores, and have peptidoglycan in their cell walls?

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