Final answer:
Cholesterol in the plasma membrane maintains its flexibility, ensuring fluidity and homeostasis by modulating membrane rigidity.
Step-by-step explanation:
The component of the plasma membrane that helps maintain its flexibility is cholesterol. Cholesterol is interspersed between the phospholipids within the plasma membrane, playing a critical role in modulating the membrane's rigidity and fluidity. In environments with lower temperatures, more cholesterol is present to ensure that the membrane remains fluid, functioning somewhat like antifreeze. This is vital for maintaining homeostasis and allowing for the proper function of membrane proteins and for the membrane to self-seal after being penetrated by something like a fine needle, as explained by the fluid mosaic model.