Which of the following statements about the function of the centrosome is true?
—-Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome—-
Centrosomes polymerize and depolymerize microtubules resulting in dynamic instability
Centrosomes load cargos onto the appropriate motor proteins for a particular destination
Centrosomes are microtubule organizing centers located near the nucleus of animal cells.
The Correct Answer and Explanation is :
Correct Answer:
Centrosomes are microtubule organizing centers located near the nucleus of animal cells.
Explanation:
The centrosome is a key cellular structure that plays a central role in organizing microtubules, the dynamic filaments involved in maintaining cell shape, intracellular transport, and cell division. Here’s why the correct answer is true, along with a breakdown of the incorrect statements:
- Correct Statement:
Centrosomes are microtubule-organizing centers (MTOCs) located near the nucleus of animal cells. They consist of two centrioles surrounded by pericentriolar material (PCM), which serves as a scaffold for the nucleation of microtubules. This nucleation is facilitated by proteins like γ-tubulin, which anchors and organizes the microtubules with their minus ends embedded in the centrosome while the plus ends extend outward. This spatial organization is crucial for cell polarity, intracellular transport, and spindle formation during mitosis. - Incorrect Statements:
- Microtubules emanating from the centrosome have alternating polarity:
This is false because microtubules radiating from the centrosome have a uniform polarity; the minus ends are anchored in the centrosome, and the plus ends extend outward into the cytoplasm. This consistent polarity is essential for directed intracellular transport mediated by motor proteins like dynein (moving toward the minus end) and kinesin (moving toward the plus end). - Centrosomes polymerize and depolymerize microtubules resulting in dynamic instability:
This is partially true but misleading. Centrosomes serve as nucleation sites for microtubule growth, but dynamic instability—the process by which microtubules alternate between growth and shrinkage—occurs primarily at the plus ends of microtubules, not within the centrosome itself. - Centrosomes load cargos onto motor proteins:
Centrosomes do not directly interact with cargo or motor proteins. Instead, they organize the microtubule network that provides tracks for motor proteins to transport cargo.
In summary, centrosomes are essential for organizing microtubule arrays and ensuring proper cellular functions such as transport, polarity, and division. The other statements misinterpret the centrosome’s specific roles or overstate its functions.