Question

According to the endosymbiont hypothesis, mitochondria are bacterial descendants because they formed as a result of a eukaryotic cell engulfing a prokaryotic cell. Based on this, what type of division would you expect to see in mitochondria?

Short answer

Binary fission.

Step-by-step solution

- Understand the Endosymbiont Hypothesis

The endosymbiont hypothesis suggests that mitochondria originated from a symbiotic relationship where a eukaryotic cell engulfed a prokaryotic cell. Over time, this prokaryotic cell evolved into the mitochondria.

- Identify the Division Mechanism of Prokaryotic Cells

Prokaryotic cells, such as bacteria, reproduce through a process known as binary fission. Binary fission is a method of asexual reproduction that involves the cell dividing into two genetically identical daughter cells.

- Apply the Hypothesis to Mitochondria

Given that mitochondria are descendants of prokaryotic cells, it is logical to assume that they would also divide in a similar manner to prokaryotic cells, which is through binary fission.

- Conclude the Type of Division in Mitochondria

Based on the endosymbiont hypothesis and the method of division in prokaryotic cells, the division type expected to be seen in mitochondria is binary fission.

Key concepts

Mitochondria

Mitochondria are essential organelles found in eukaryotic cells. They are often called the 'powerhouses of the cell' because they produce most of the cell's supply of adenosine triphosphate (ATP), which is used as a source of chemical energy. Mitochondria have their own DNA, which is circular and similar to the DNA of prokaryotic cells. This unique feature supports the endosymbiont hypothesis, which suggests that mitochondria originated from free-living prokaryotes.
Mitochondria are also involved in other critical tasks such as regulating the cell cycle and cell growth, signaling, cellular differentiation, and controlling the cell’s metabolism. Given their bacterial ancestry, mitochondria share several similarities with prokaryotic cells, particularly in their division process.

Binary Fission

Binary fission is the process by which prokaryotic cells, such as bacteria, reproduce. In this method of asexual reproduction, a single cell divides into two genetically identical daughter cells. The binary fission process involves the replication of the cell's DNA, segregation of the copied DNA, and splitting of the cell into two.
There are several steps in binary fission:

• The DNA of the cell replicates.
• The cell grows in size and the two copies of DNA move to opposite poles of the cell.
• A septum forms, beginning the process of division.
• The cell officially splits into two daughter cells, each with a complete set of identical DNA.

Given their prokaryotic origin, mitochondria also divide by binary fission, which points back to the endosymbiont hypothesis.

Prokaryotic Cells

Prokaryotic cells are simple, single-celled organisms that lack a nucleus and membrane-bound organelles. Bacteria and archaea are the primary examples of prokaryotic life forms. Their DNA is circular and floats freely within the cell in a region called the nucleoid.
Some distinctive features of prokaryotic cells include:

• A cell wall that provides structural support and protection.
• Plasma membrane separating the interior of the cell from the outside environment.
• Ribosomes for protein synthesis; however, they are smaller than those in eukaryotic cells.

Prokaryotic cells are essential in many ecosystems and can perform astonishing metabolic diversity. Their method of division by binary fission has been inherited by mitochondria, these descendants of ancient symbiotic events.

Eukaryotic Cells

Eukaryotic cells are more complex than prokaryotic cells and contain a nucleus and various membrane-bound organelles. These organelles perform specialized functions within the cell. Examples of eukaryotic organisms include plants, animals, fungi, and protists.
Some key characteristics of eukaryotic cells are:

• A well-defined nucleus that houses DNA organized into chromosomes.
• Mitochondria for energy production, and other organelles such as the endoplasmic reticulum, Golgi apparatus, and lysosomes.
• A cytoskeleton for structural support and intracellular transport.

The endosymbiont hypothesis suggests that certain organelles found in eukaryotic cells, like mitochondria, originated from ancient symbioses with prokaryotic cells. This evolutionary relationship highlights the significance of prokaryotic cells in the development of complex life forms.