The lifetime of a microtubule in a mammalian cell, between...

The lifetime of a microtubule in a mammalian cell, between its formation by polymerization and its spontaneous disappearance by depolymerization, varies with the stage of the cell cycle. For an actively proliferating cell, the average lifetime is 5 minutes in interphase and 15 seconds in mitosis. If the average length of a microtubule in interphase is $20 \mu \mathrm{m},$ how long will it be during mitosis, assuming that the rates of microtubule elongation due to the addition of tubulin subunits in the two phases are the same?

Key Concepts

Microtubule Dynamics

This concept encompasses the rapid and continual process of microtubule assembly (polymerization) and disassembly (depolymerization) that occurs in cells. It is fundamental to understanding how microtubules can change in length and stability depending on cellular conditions, such as different phases of the cell cycle.

Cell Cycle Phases

The cell cycle consists of distinct phases, most notably interphase and mitosis, during which cellular activities, including microtubule behavior, are tightly regulated. The varying lifetimes of microtubules in these phases illustrate how the cell adjusts the dynamic properties of its cytoskeleton to meet functional requirements.

Polymerization Rate

The polymerization rate refers to the constant speed at which tubulin subunits are added to extend the microtubule. When this rate is uniform, the final length of a microtubule is directly proportional to its lifetime, making it a crucial factor in predicting changes in microtubule length under different cellular conditions.

Proportional Reasoning in Biology

This mathematical concept involves relating two quantities, such as microtubule length and lifetime, when changes in one correspond to proportional changes in the other. In this instance, it allows for the determination of microtubule length during mitosis based on the known parameters during interphase.

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