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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 5
Chapter 4, Problem 5

Which of the following statements best describes what happens to a cell exposed to polymyxins that destroy phospholipids?
a. In an isotonic solution, nothing will happen.
b. In a hypotonic solution, the cell will lyse.
c. Water will move into the cell.
d. Intracellular contents will leak from the cell.
e. Any of the above might happen.

Verified step by step guidance
1
Step 1: Understand the mechanism of action of polymyxins. Polymyxins are antibiotics that target and disrupt the phospholipid components of the bacterial cell membrane, compromising its integrity.
Step 2: Recognize that phospholipids are essential for maintaining the cell membrane's selective permeability and structural stability. When polymyxins destroy phospholipids, the membrane becomes damaged and leaky.
Step 3: Analyze the consequences of membrane damage. A compromised membrane allows intracellular contents to leak out because the barrier that normally contains these substances is disrupted.
Step 4: Consider the effect of the surrounding solution's tonicity. While tonicity affects water movement, the primary effect of polymyxin-induced membrane damage is leakage of cell contents rather than osmotic swelling or shrinking.
Step 5: Conclude that the best description of what happens to a cell exposed to polymyxins is that intracellular contents leak from the cell due to membrane disruption.

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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 Polymyxins

Polymyxins are antibiotics that target and disrupt the phospholipid components of bacterial cell membranes, increasing membrane permeability. This disruption compromises the membrane's integrity, leading to leakage of intracellular contents and ultimately cell death.
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Role of Phospholipids in Cell Membrane Integrity

Phospholipids form the fundamental bilayer structure of cell membranes, providing a selective barrier that controls the movement of substances in and out of the cell. Damage to phospholipids weakens this barrier, causing loss of membrane function and leakage of cellular materials.
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Effects of Osmotic Conditions on Cells

Osmotic conditions (isotonic, hypotonic, hypertonic) influence water movement across membranes. However, if the membrane is compromised by agents like polymyxins, the primary effect is leakage of cell contents rather than osmotic swelling or shrinking.
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Related Practice
Textbook Question

Which of the following is false about fimbriae?

a. They are composed of protein.

b. They may be used for attachment.

c. They are found on gram-negative cells.

d. They are composed of pilin.

e. They may be used for motility.

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Textbook Question

Compare and contrast the following:

a. Simple diffusion and facilitated diffusion

b. Active transport and facilitated diffusion

c. Active transport and group translocation

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Textbook Question

Match the structures in column A to their functions in column B.

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Textbook Question

Answer the following questions using the diagrams provided, which represent cross sections of bacterial cell walls.

a. Which diagram represents a gram-positive bacterium? How can you tell?

b. Explain how the Gram stain works to distinguish these two types of cell walls.

c. Why does penicillin have no effect on most gram-negative cells?

d. How do essential molecules enter cells through each wall?

e. Which cell wall is toxic to humans?

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Textbook Question

Use the following choices to answer the following question.

a. No change will result; the solution is isotonic.

b. Water will move into the cell.

c. Water will move out of the cell.

d. The cell will undergo osmotic lysis.

e. Sucrose will move into the cell from an area of higher concentration to one of lower concentration.


Which statement best describes what happens when a gram-positive bacterium is placed in an aqueous solution of lysozyme and 10% sucrose?

Textbook Question

Why is an endospore called a resting structure? Of what advantage is an endospore to a bacterial cell?

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