The figure below shows a mitochondrion, emphasizing its inner and outer membranes.
The inner membrane of the mitochondria is thought to have evolved from
A)a bit of plasma membrane from the early eukaryotic cell that engulfed a bacterium.
B)the membrane surrounding the lysosome that engulfed a bacterium once it was inside an early eukaryotic cell.
C)the plasma membrane of a prokaryotic cell engulfed by an early eukaryotic cell.
D)infoldings of the plasma membrane of an early eukaryotic cell.

Question

The figure below shows a mitochondrion, emphasizing its inner and outer membranes. 
The inner membrane of the mitochondria is thought to have evolved from
A)a bit of plasma membrane from the early eukaryotic cell that engulfed a bacterium. 
B)the membrane surrounding the lysosome that engulfed a bacterium once it was inside an early eukaryotic cell. 
C)the plasma membrane of a prokaryotic cell engulfed by an early eukaryotic cell. 
D)infoldings of the plasma membrane of an early eukaryotic cell.

Quizplus · Accepted Answer

The inner membrane of the mitochondria is thought to have evolved from the plasma membrane of a prokaryotic cell that was engulfed by an early eukaryotic cell. This theory is known as the endosymbiotic theory and suggests that mitochondria were once free-living bacteria that were engulfed by an ancient eukaryotic cell. Over time, these bacteria evolved into mitochondria, and their outer membrane fused with the plasma membrane of the host cell while their inner membrane retained its bacterial characteristics.

The Figure Below Shows a Mitochondrion, Emphasizing Its Inner and Outer