BIOS 251 Week 3 Case Study: Cells

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Chamberlain University

BIOS-251 Anatomy & Physiology I

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BIOS 251 Week 3 Case Study: Cells

Mutation in Mitochondrial DNA

Brian highlights that a mutation is present in a gene located within the mitochondrial DNA (mtDNA). Unlike nuclear DNA, mitochondrial DNA is inherited solely from the mother and resides in the mitochondria, which are essential energy-producing centers of the cell. The identified mutation is linked to Leber Hereditary Optic Neuropathy (LHON), a genetic disorder that leads to vision loss. Since mitochondria supply the majority of cellular energy, a mutation within the mtDNA can disrupt energy production and compromise the normal function of cells. In the case of the optic nerve, this energy deficiency may cause nerve cells to degenerate, leading to impaired vision.

The Role of Mitochondria in Cellular Function

Mitochondria play a vital role in sustaining life by providing the energy needed for cellular processes. As stated by Gahl (n.d.), “Mitochondria are membrane-bound organelles (mitochondrion, singular) that generate most of the chemical energy needed to power the cell’s biochemical reactions” (para. 1). This energy is stored in the form of adenosine triphosphate (ATP), which fuels essential biochemical activities.

Structurally, mitochondria contain two membranes: the outer membrane and the inner membrane. The outer membrane acts as a protective barrier, while the inner membrane is folded into structures called cristae, which expand the surface area for energy production. This wrinkled structure is directly related to the mitochondria’s efficiency in producing ATP.

Structural Differences Between Mitochondria and the Cell Membrane

The mitochondria differ significantly from the typical eukaryotic cell membrane. The following table highlights key differences between them:

Feature	Mitochondria	Cell Membrane (Plasma Membrane)
Structure	Double membrane (outer and inner)	Phospholipid bilayer
Inner Structure	Inner membrane folds into cristae	Lacks cristae; flat bilayer
Primary Function	Energy (ATP) production	Regulation of transport of molecules in/out
Energy Role	Generates ATP through cellular respiration	Maintains homeostasis and communication
Genetic Material	Contains its own DNA (mtDNA)	No DNA present

Possible Mechanisms of Vision Loss in LHON

While the exact mechanism of optic nerve cell death in LHON is not fully understood, several hypotheses exist. One possibility is that defective mitochondria fail to produce sufficient ATP, depriving optic nerve cells of the energy needed to maintain function. This energy shortage may lead to cell death and progressive vision loss. Another explanation is the inheritance pattern of mitochondrial mutations, which pass maternally and affect multiple family members.

In addition, oxidative stress has been suggested as a contributing factor. Damaged mitochondria may produce excessive reactive oxygen species (ROS), leading to oxidative injury in sensitive nerve tissues (Yu-Wai-Man et al., 2020). This combination of impaired energy supply and oxidative stress can accelerate the degeneration of optic nerve cells.

References

Gahl, W. A. (n.d.). Mitochondria. MedlinePlus Genetics. Retrieved from https://medlineplus.gov/genetics/understanding/cells/mitochondria/

BIOS 251 Week 3 Case Study: Cells

Yu-Wai-Man, P., Griffiths, P. G., Burke, A., Sellar, P. W., Clarke, M. P., Gnanaraj, L., … & Chinnery, P. F. (2020). The prevalence and natural history of dominant optic atrophy due to OPA1 mutations. Ophthalmology, 127(2), 240-248. https://doi.org/10.1016/j.ophtha.2019.09.012