Multiple Choice
According to the endosymbiotic theory, how did chloroplasts end up in producers’ cells?
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1. Overview of Cell Biology
Evolution of the Cell
Multiple Choice
In the context of the evolution of the eukaryotic cell, the best-supported explanation for how mitochondria and chloroplasts arose is which of the following?
A
Nuclear budding: mitochondria and chloroplasts originated as vesicles that budded from the nucleus and later acquired metabolic enzymes
B
Endosymbiosis: an ancestral eukaryotic cell engulfed aerobic bacteria (becoming mitochondria) and later engulfed photosynthetic cyanobacteria (becoming chloroplasts), with the symbionts retained as organelles
C
Autogenous origin: mitochondria and chloroplasts formed de novo by invagination and specialization of the eukaryotic plasma membrane
D
Spontaneous generation: mitochondria and chloroplasts repeatedly assembled from nonliving cellular components whenever energy demands increased
Verified step by step guidance1
Understand the concept of endosymbiosis, which proposes that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by an ancestral eukaryotic cell.
Recognize the evidence supporting endosymbiosis, such as mitochondria and chloroplasts having their own DNA, double membranes, and similarities to certain bacteria in size and reproduction.
Compare the endosymbiotic theory with alternative hypotheses like nuclear budding, autogenous origin, and spontaneous generation, noting that these lack strong experimental or observational support.
Focus on how the engulfed aerobic bacteria evolved into mitochondria, providing the host cell with efficient energy production, and how photosynthetic cyanobacteria became chloroplasts, enabling photosynthesis.
Conclude that the endosymbiotic theory best explains the origin of mitochondria and chloroplasts due to its strong molecular, genetic, and structural evidence.
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