_____are intracellular organelles that provide the cell's energy stores and are commonly referred to as the "powerhouse" of the cell. H


_____contains proteins that transport large molecules needed to carry out mitochondrial functions.

Outer mitochondrial membrane

inner mitochondrial matrix

invaginates to form cristae, and these numerous folds provide a large surface area for the reactions that occur on this membrane. Numerous transmembrane proteins, including proteins of the electron transport chain (ETC), as well as those needed to maintain the proton gradient between the intermembrane space and the matrix, maintain the inner membrane's selective permeability.

Mitochondria contain enzymes needed for the processes of

fatty acid β-oxidation, acetyl-CoA production, ketogenesis, the tricarboxylic acid (TCA) cycle (or Krebs cycle), and oxidative phosphorylation.

Mitochondria are the cell's primary site of _______ via aerobic respiration

ATP production

Mitochondria are also important for determining whether a cell will die via programmed cell death, known as


When a mitochondrion releases________, normally an electron carrier of the ETC, apoptosis is triggered, and the cell dies. Mitochondria are also thought to play a role in determining which oocyte is released during the ovulation cycle.

Cytochrome C

What is the mitochondrial matrix?

The mitochondrial matrix is the name of the lumen surrounded by the inner mitochondrial membrane.

Mitochondria have their ______ sometimes referred to as the "47th chromosome.

own DNA (mtDNA),

A _______of double-stranded DNA housed in the mitochondrial matrix

circular piece of dsDNA

The remainder of the genes code for ____________that both the cell and the mitochondrion use during protein synthesis, called translation. Unlike the nuclear genome, mtDNA does not use histones.

transfer RNAs (tRNAs)

mtDNA does not use


main difference between mtDNA and nuclear DNA is the use of a slightly different genetic code.

UGA triplet codes for the amino acid tryptophan in mtDNA instead of serving as a stop codon, as it does in nuclear DNA. => In mtDNA, the codons AGA and AGG serve as stop codons instead of coding for the amino acid arginine.

mtDNA mutation rate is 10x higher than that of the nuclear genome due to the lack of ____________compared with what is found within the nucleus and to damage by ROS common byproducts of mitochondria reactions

lack of DNA repair mechanisms

Mitochondria divide by prokaryotic ______

binary fission

How does mtDNA differ from nuclear DNA?

mtDNA is circular, does not contain histones, and has a higher mutation rate than nuclear DNA

______s are caused by mutations in mtDNA. Some examples of mitochondrial diseases include mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS); Leber hereditary optic neuropathy (LHON); and myoclonic epilepsy with ragged red fibers (MERRF).

Mitochondrial diseases

Examples of mitochondrial diseases

Leber hereditary optic neuropathy, myocolonic epilepsy with ragged red fibers (MERRF)

_____is a mitochondrial myopathy that presents within the first decade of life. Muscle biopsy shows characteristic ragged-red fibers, which are formed from an accumulation of diseased mitochondria


Ragged red muscle fibers

mitochondrial myopathy

mitochondrial myopathy

genetic mitochondrial abnormalities that prevent muscles from producing energy

mitochondrial myopathy presentation

WeaknessPoor enduranceDiscomfortExertional dyspneaTachycardia

mitochondria inheritance

1. inherited from the mother - from large egg, do not survive in sperm2. relatively high mutation rates due to absence of DNA repair mechanisms

hallmark of mitochondrial diseases is their ________When cells divide, mtDNA replicates and randomly assorts among mitochondria

variable transmission and presentation.


Presence of both normal and mutated mtDNA, resulting in variable expression in mitochondrial inherited disease


presence of only one version of DNA within the cytoplasm of a single cell

Leber hereditary optic neuropathy (LHON)

is a mitochondrial disease characterized by sudden, painless vision loss in both eyes in the late teens or early twenties. Males are predominantly affected, but females can develop LHON later in life and are often more severely affected.To be at risk for developing this condition, one must be homoplasmic for the LHON mutation or have a very high percentage of mutant mtDNA within the optic neurons.

mitochondrial diseases manifest only after _______, or threshold, required by the system.

ATP production falls below the level

What is heteroplasmy?

Heteroplasmy describes cells that contain some mitochondria with normal mtDNA and some mitochondria with mutant mtDNA.

_____ describes cells with a uniform collection of mtDNA, either all normal mtDNA or all mutant mtDNA.


____describes cells that contain both mitochondria with normal mtDNA and mitochondria with mutant mtDNA.


Which of the following statements accurately describes the structure of a mitochondrion?

Contains its own DNA=> Mitochondria contain their own circular, double-stranded piece of mitochondrial DNA (mtDNA) that encodes for mitochondria-specific proteins. Mitochondria divide by binary fission, not mitosis

Which of the following metabolic pathways does not take place in mitochondria?

Glycolysis=> Glycolysis takes place solely in the cell's cytoplasm

Metabolic pathways that occur solely in the mitochondria include the

Electron transport chain, FA Beta oxidation, oxidative phosphorylation and the TCA cycle

Mitochondria also contain some of the enzymes needed for

- heme synthesis- urea cycle-gluconeogenesis

child is referred to your clinic for a suspected mitochondrial disorder. Mitochondrial DNA sequencing shows that some cells contain both normal mitochondria and mutant mitochondria. What is this known as?

Heteroplasmy =>describes cells that contain both normal and mutant mitochondrial DNA (mtDNA).

Homoplasmy describes cells that contain only _____type of mtDNA, it can either be all normal or all mutant

one type of mtDNA

A teenage boy comes to your clinic with sudden, painless vision loss. His mother says that both her older and younger brothers experienced this in their late teens, but none of their children seem to be affected. You suspect a mitochondrial disease. Which of the following statements supports this type of disease?

Maternal pattern of inheritance=> his boy's family is likely affected by Leber hereditary optic neuropathy (LHON), a mitochondrially inherited condition. Mitochondrial diseases can affect both males and females but are only transmitted through females.=> this explains why this patient's uncles are affected but their children are not