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Multiple Choice
In the context of prokaryotic cell architecture, which organelle is absent in Escherichia coli?
A
70S ribosomes
B
Plasma membrane
C
Cell wall (peptidoglycan layer)
D
Membrane-bound nucleus
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Verified step by step guidance
1
Step 1: Understand the basic structure of prokaryotic cells like Escherichia coli. Prokaryotes lack membrane-bound organelles, which distinguishes them from eukaryotic cells.
Step 2: Identify the organelles listed in the problem: 70S ribosomes, plasma membrane, cell wall (peptidoglycan layer), and membrane-bound nucleus.
Step 3: Recall that 70S ribosomes are present in prokaryotes and are responsible for protein synthesis, unlike the 80S ribosomes found in eukaryotes.
Step 4: Recognize that the plasma membrane and cell wall (made of peptidoglycan) are essential structural components of Escherichia coli, providing protection and regulating transport.
Step 5: Conclude that the membrane-bound nucleus is absent in Escherichia coli because prokaryotes do not have a nucleus; their genetic material is located in the nucleoid region without a surrounding membrane.