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 2

Chapter 4, Problem 2

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 distilled water and penicillin?

Verified step by step guidance

Step 1: Understand the environment and the bacterium involved. A gram-positive bacterium has a thick peptidoglycan cell wall that provides structural support and protection against osmotic pressure.

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

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

Step 4: Combine the effects. With a weakened cell wall due to penicillin and water moving into the cell from the hypotonic environment, the cell is likely to swell and eventually burst.

Step 5: Conclude which choice best fits this scenario. The cell will undergo osmotic lysis because the weakened cell wall cannot withstand the influx of water.

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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 low solute concentration to high solute concentration. When a bacterium is placed in distilled water, which is hypotonic relative to the cell interior, water tends to move into the cell, potentially causing swelling.

Cell Wall Structure of Gram-Positive Bacteria

Gram-positive bacteria have a thick peptidoglycan cell wall that provides structural support and protects against osmotic pressure. This rigid wall helps maintain cell shape and prevents bursting under hypotonic conditions, but damage to it can compromise cell integrity.

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 (bursting).

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Textbook Question

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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Textbook Question

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.

a. Spiral

b. Bacillus

c. Coccus

d. Spirochetes

e. Staphylococci

f. Streptobacilli

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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.