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Multiple Choice
Chloroplasts and mitochondria are thought to be of prokaryotic origin. One piece of evidence that supports this hypothesis is that these organelles contain prokaryotic-like ribosomes. These ribosomes are probably most similar to ribosomes found __________.
A
free in the cytoplasm of eukaryotes
B
on the rough ER
C
free in the cytoplasm of eukaryotes and on the rough ER
D
free in the cytoplasm of eukaryotes, on the rough ER, and in bacterial cells
E
in bacterial cells
Verified step by step guidance
1
Understand the endosymbiotic theory, which suggests that chloroplasts and mitochondria originated from prokaryotic cells that were engulfed by ancestral eukaryotic cells.
Recognize that chloroplasts and mitochondria have their own DNA and ribosomes, which are similar to those found in prokaryotic cells, supporting the idea of their prokaryotic origin.
Identify the types of ribosomes: eukaryotic cells have 80S ribosomes, while prokaryotic cells have 70S ribosomes. Chloroplasts and mitochondria contain 70S ribosomes, similar to those in prokaryotes.
Consider the options given: ribosomes free in the cytoplasm of eukaryotes and on the rough ER are 80S, whereas ribosomes in bacterial cells are 70S.
Conclude that the ribosomes in chloroplasts and mitochondria are most similar to those found in bacterial cells, as they share the same 70S structure.