Annexin Visa marker of
**Core Concept**
Annexin V is a protein that binds to phosphatidylserine (PS), a phospholipid component of cell membranes. In normal cells, PS is primarily located on the inner leaflet of the cell membrane, but in apoptotic cells, it is translocated to the outer leaflet, making it a marker for apoptosis.
**Why the Correct Answer is Right**
Annexin V is used as a marker for apoptosis because it has a high affinity for PS. This binding is specific and can be detected using techniques such as flow cytometry or fluorescence microscopy. The binding of Annexin V to PS is a result of the electrostatic interactions between the positively charged Annexin V and the negatively charged PS. This interaction is reversible and can be disrupted by the addition of calcium ions or other molecules that compete with Annexin V for binding to PS.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Annexin V does not bind to phosphatidylethanolamine (PE), but rather to phosphatidylserine (PS).
**Option B:** This option is incorrect because Annexin V is not a marker for necrosis, but rather for apoptosis.
**Option C:** This option is incorrect because Annexin V is not a marker for cell proliferation, but rather for cell death.
**Clinical Pearl / High-Yield Fact**
Annexin V is a useful marker for detecting apoptosis in various cell types, including cancer cells, and can be used to monitor the effectiveness of anti-cancer therapies.
**Correct Answer: A. Annexin V is a marker of apoptosis.**