Answer:
Microtubules are tiny cylindrical structures that are a part of the cytoskeleton, which is a network of protein filaments that help maintain the shape and structure of cells.
The polarity of microtubules refers to the difference in the ends of the stick-like structures inside cells.
Microtubules have different ends because of the arrangement of their building blocks, and this polarity is related to their organization and intracellular movements within the cell.
The polarity of the microtubule exists not only at the two ends of the filament, but all along the length of its lattice. This is critical for the movement along the microtubule of molecular motor proteins, which are enzymes that walk specifically toward either the plus end or the minus end of the microtubule.
Step-by-step explanation:
1. Microtubules are long, thin, tube-like structures found in cells.
2. They have two ends, one called the plus end and the other the minus end.
3. The plus end grows faster than the minus end.
4. The polarity of microtubules is based on the arrangement of their building blocks, called tubulintubulintubulin.
5. Microtubule polarity helps to organize them within the cell and determines the direction
of intracellular movements powered by microtubule-dependent motors.
6. The polarity of microtubules gives advantages for proper cell function by allowing them to move materials and structures in specific directions.
What to watch: The arrangement of tubulin proteins and their effect on the polarity of microtubules.
Example: A train track can be compared to a microtubule because it has two ends and can only move in one direction.
Real-world example: Microtubules are responsible for the movement of chromosomes
during cell division, ensuring that they are divided equally between daughter cells.
The polarity of microtubules is based on the arrangement of α- and β-tubulin subunits that make up the filament. Each subunit has a slightly different conformation and interacts with its neighbor differently. In the microtubule, the β-tubulin subunits are oriented toward the plus end, and the α-tubulin subunits are oriented toward the minus end, resulting in a polar filament.
This polarity is important for microtubule organization within the cell. In general, microtubules with their plus ends facing outward are organized in a radial array from the centrosome, while microtubules with their plus ends facing inward can form spindle fibers during cell division. The organization of microtubules within the cell is crucial for proper cellular function, including cell division, intracellular transport, and the maintenance of cell shape.
The polarity of microtubules is also critical for the intracellular movements powered by microtubule-dependent motors. These motors, including kinesins and dyneins, move along microtubules in a polar manner, with kinesins moving towards the plus end and dyneins moving towards the minus end. This directional movement allows for the transport of organelles, vesicles, and other cargoes to their proper destination within the cell.
The advantages of microtubule polarity for proper cell function include precise organization of cellular structures and efficient intracellular transport. The ability to precisely regulate the orientation and organization of microtubules is essential for proper cell division, differentiation, and development. The directional movement of microtubule-dependent motors allows for the transport of cellular components and signaling molecules to their proper destination, facilitating cell function and communication.
NIH
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