How mitochondria adapted to living within cells

How mitochondria adapted to living within cells

Subject: Science and Tech

Section: Basic science

Context: An organism that has been around from 2 billion years ago has given biologists from Centre for Cellular and Molecular Biology, Hyderabad (CCMB), a clue as to how mitochondria became an inseparable part of animal and plant cells

Findings:

• Today, mitochondria are well known to be integral parts of the eukaryotic cell. They are dubbed the power houses of the cell, because they help in generating energy in the form of ATP within the cell, powering it. But they were not always part of the animal and plant cells.
• Once, about two billion years ago, a prokaryotic organism (without a nucleus) called archaea captured a bacterial cell. The bacterial cell learnt to live within the archaea as an endosymbiont.
• In the late 19th century, observed that organelles like chloroplast [and later mitochondria] undergo division inside eukaryotic cells that resembles bacterial division, which led them to suspect that these organelles might have arisen from bacterial endosymbionts
• By studying an organism known as jakobid, which has been around since before animals and fungi branched off from plants and algae in the process of evolution, the researchers have identified two adjustments that had to take place to facilitate the integration of the two organisms.
• These adjustments were made in the process of optimisation when the two organisms merged together, evidently for compatibility. The researchers show that these changes, in a protein (DTD) and a tRNA (carrying an amino acid glycine for protein synthesis) are crucial for the successful emergence of mitochondria.

Mitochondria

• Mitochondria are known as the powerhouse of the cell.
• The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine Triphosphate) molecules.
• ATP is known as the energy currency of the cell.

• The body uses energy stored in ATP for making new chemical compounds and for mechanical work.
• Mitochondria have two membrane coverings instead of just one.
• The outer membrane is very porous while the inner membrane is deeply folded. These folds create a large surface area for ATP-generating chemical reactions.
• Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes. Therefore, mitochondria are able to make some of their own proteins.

Prokaryotic Cells vs. Eukaryotic Cells

• Organisms whose cells lack a nuclear membrane, are called prokaryotes
• Organisms with cells having a nuclear membrane are called eukaryotes.
• Prokaryotic cells also lack most of the other cytoplasmic organelles present in eukaryotic cells.
• Many of the functions of such organelles are also performed by poorly organised parts of the cytoplasm.
• The chlorophyll in photosynthetic prokaryotic bacteria is associated with membranous vesicles (bag like structures) but not with plastids as in eukaryotic cells.
• Prokaryotes therefore has defined nuclear region, the membrane-bound cell organelles are absent.
• Eukaryotic Cells have nuclear membrane as well as membrane-enclosed organelles.

Jakobid

Jakobids are an order of free-living, heterotrophic, flagellar eukaryotes in the supergroup Excavata. They are small (less than 15 μm), and can be found in aerobic and anaerobic environments.