Mito-Nuc CSF 2

Endosymbiotic Theory

A scientific theory stating that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by an archaeal host cell, leading to a symbiotic relationship.

Scientific Theory

A well-substantiated explanation of an aspect of the natural world, supported by a vast body of evidence (e.g., Germ Theory, Theory of Evolution).

Archaea

A domain of single-celled microorganisms with distinct biochemistry from Bacteria; believed to be the host cell that engulfed the alphaproteobacterium in endosymbiosis.

Bacteria

A domain of single-celled microorganisms; the alphaproteobacterium group is the ancestor of mitochondria.

The Great Oxygen Event

A period around 2.4 billion years ago when oxygen levels rose dramatically due to cyanobacterial photosynthesis, creating pressure for efficient oxygen-based metabolism.

The "Ox-Tox" Hypothesis

A hypothesis for endosymbiosis where the host archaeon engulfed the alphaproteobacterium for its ability to detoxify oxygen.

The Hydrogen Hypothesis

A hypothesis for endosymbiosis where an archaeon reliant on hydrogen engulfed a hydrogen-producing bacterium, forming a metabolic dependency.

Hydrogenosome

An organelle found in some anaerobic eukaryotes that produces energy and hydrogen; thought to be a highly modified mitochondrion.

Mitochondrion

An organelle in eukaryotic cells that produces energy (ATP) via oxidative phosphorylation and performs other key functions.

Chloroplast

An organelle in plant and algal cells that performs photosynthesis; evolved from an endosymbiotic cyanobacterium.

Nitroplast

A recently discovered organelle in a marine alga that fixes nitrogen; the first known nitrogen-fixing organelle originating from an endosymbiotic cyanobacterium.

Mitochondrial Structure

Has a double membrane; the inner membrane is highly folded into cristae to increase surface area for ATP production.

Cell Migration

The movement of cells; mitochondria provide localized energy and regulate calcium, which is crucial for this process.

Calcium Homeostasis

The regulation of calcium ion levels in the cell; mitochondria act as a calcium buffer, storing and releasing Ca2+ to control signaling and metabolism.

Heat Shock Response

A cellular response to high temperatures; mitochondria generate heat during OXPHOS, activating Heat Shock Factor 1 (HSF1) to protect proteins from misfolding.

Inflammation

An immune response; can be triggered when mitochondrial DNA (mtDNA) is released into the cytosol during mitophagy, activating inflammatory pathways.

OMVs (Outer Membrane Vesicles)

Vesicles budded from the outer membrane of bacteria; in early endosymbiosis, OMVs from the engulfed bacterium are hypothesized to have seeded the host's endomembrane system.

Mitogenome

The mitochondrial genome; a small, circular DNA molecule that is maternally inherited and has a high mutation rate.

NuMTs (Nuclear Mitochondrial Segments)

Pieces of mitochondrial DNA that have been transferred and integrated into the nuclear genome over evolutionary time.

Plastid

A general term for organelles like chloroplasts; their genome is called the plastome.

Electron Transport System

A series of protein complexes (I-IV) in the inner mitochondrial membrane that transfer electrons to create a proton gradient.

Oxidative Phosphorylation (OXPHOS)

The process of ATP production driven by the proton gradient created by the Electron Transport System; involves Complexes I-V.

Incompatibility

Problems that arise when proteins encoded by the nuclear genome and the mitochondrial genome do not interact properly, leading to mitochondrial dysfunction and disease.

Reactive Oxygen Species (ROS)

Highly reactive molecules (e.g., superoxide) produced as a byproduct of OXPHOS; function as signaling molecules at low levels but cause oxidative damage at high levels.

Antioxidants

Molecules (e.g., superoxide dismutase - Sod) that neutralize ROS, preventing oxidative damage to cells.

Heteroplasmy

The condition where a cell contains a mixture of mitochondrial DNA types (e.g., wild-type and mutant).

Threshold Effect

The phenomenon where symptoms of a mitochondrial disease only appear once the proportion of mutant mtDNA (heteroplasmy level) exceeds a certain threshold.

Paternal Leakage

The rare introduction of paternal mitochondria into the zygote, which are typically destroyed by mechanisms like ubiquitination or enzymatic degradation (e.g., EndoG).

Mother’s Curse

The concept that maternally inherited mitochondrial mutations that are harmful only to males can accumulate because they are not selected against in females.