Ch. 4 - Functional Anatomy of Prokaryotic and Eukaryotic Cells

Tortora - Microbiology: An Introduction 14th Edition

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Tortora 14th Edition

Ch. 4 - Functional Anatomy of Prokaryotic and Eukaryotic Cells

Problem 3

Chapter 4, Problem 3

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-negative bacterium is placed in distilled water and penicillin?

Verified step by step guidance

Step 1: Understand the environment and the bacterium's characteristics. A gram-negative bacterium has a thin peptidoglycan layer and an outer membrane, which affects its response to osmotic changes and antibiotics like penicillin.

Step 2: Analyze the effect of distilled water on the bacterium. Distilled water is hypotonic relative to the bacterial cytoplasm, so water tends to move into the cell by osmosis.

Step 3: Consider the role of penicillin. Penicillin inhibits the synthesis of peptidoglycan, weakening the bacterial cell wall and making the cell more susceptible to osmotic pressure.

Step 4: Combine the effects. Since water moves into the cell and the cell wall is weakened by penicillin, the bacterium is likely to swell and potentially burst due to osmotic lysis.

Step 5: Match the scenario to the correct statement. The best description is that the cell will undergo osmotic lysis because of water influx and weakened cell wall integrity caused by penicillin.

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Key Concepts

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

Osmosis and Tonicity

Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to higher solute concentration. When a bacterium is placed in distilled water, which is hypotonic relative to the cell's interior, water tends to move into the cell, potentially causing swelling.

Cell Wall Structure of Gram-Negative Bacteria

Gram-negative bacteria have a thin peptidoglycan layer surrounded by an outer membrane. This structure provides some protection but is less rigid than gram-positive walls, making them more susceptible to damage from agents like penicillin that target cell wall synthesis.

Mechanism of Action of Penicillin

Penicillin inhibits the synthesis of peptidoglycan, weakening the bacterial cell wall. In a hypotonic environment like distilled water, this weakened wall cannot withstand osmotic pressure, leading to cell swelling and eventual osmotic lysis.

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Endospore formation is called (a) ________. It is initiated by (b) ________. Formation of a new cell from an endospore is called (c) ________. This process is triggered by (d) ________.

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

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Draw the bacterial shapes listed in (a), (b), and (c). Then draw the shapes in (d), (e), and (f), showing how they are special conditions of a, b, and c, respectively.

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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.