Which structures perform the function of mitochondria in bacteria?
A. Nucleoid
B. Ribosomes
C. Cell wall
D. Mesosomes

Hint:-Mitochondrion is a double-membrane-bound organelle present in most eukaryotic organisms. They are located within the cytoplasm and act as the digestive mechanism of the cell. They play a major role in nutrient degradation and generate energy-rich molecules in cells. Therefore, they are also identified as the Powerhouse of the Cell.

Complete Answer:-Mitochondria are the powerhouses of a cell. It is a tiny organelle that floats in the cell. They are made up of two membranes, the outer and inner membrane. The inner membrane is covered with layered structures called cristae and the outer membrane is covered with skins. The role of mitochondria is to generate energy from the cell and control cellular metabolism. Like mesosomes, the mitochondrial cell membranes of bacteria are folded.
In bacteria, mesosomes fulfill the role of mitochondria. Mesosomes are bacterial organelles that exist on the plasma membrane and function either in the replication of DNA and division of cells or in the excretion of exoenzymes. Generally, mesosomes are located in association with the nuclear region or at the site of cell division. They are absent in eukaryotes. Since mitochondria are the respiratory site, the bacteria induce respiration from these mesosomes and therefore they are rich in enzymes.

Therefore, the correct answer is option D.

Note:- Mesosomes also have a role in reproduction. A cross-wall is created during binary fission, resulting in the creation of two cells. Mesosomes begin septum formation and bind bacterial DNA to the membrane of the cell. It divides and separates each daughter cell from the bacterial DNA.