A mitochondrial marker enzyme is:
**Core Concept**
Mitochondrial marker enzymes are crucial in identifying the presence and function of mitochondria in cells. These enzymes are specific to the mitochondria and are used as markers to assess mitochondrial damage or dysfunction in various diseases.
**Why the Correct Answer is Right**
The correct answer is **Cytochrome c oxidase**. This enzyme is a crucial component of the electron transport chain in mitochondria, responsible for the transfer of electrons from cytochrome c to oxygen, resulting in the production of ATP. The presence of cytochrome c oxidase in a cell is a reliable indicator of mitochondrial function.
**Why Each Wrong Option is Incorrect**
**Option A:** Lactate dehydrogenase is a marker of cellular damage, but it is not specific to mitochondria. It is found in both the mitochondria and the cytosol of cells.
**Option B:** Glucose-6-phosphate dehydrogenase is an enzyme involved in the pentose phosphate pathway, but it is not a marker of mitochondrial function.
**Option C:** Creatine kinase is an enzyme involved in energy metabolism, but it is primarily found in the cytosol of muscle cells and is not a specific marker of mitochondrial function.
**Clinical Pearl / High-Yield Fact**
It's essential to note that mitochondrial dysfunction is associated with various diseases, including neurodegenerative disorders, metabolic disorders, and cancer. Identifying mitochondrial marker enzymes is critical in diagnosing and managing these conditions.
**Correct Answer:** C. Cytochrome c oxidase