Why do tiny mosfets that are used to move charge onto and off the capacitors limit the speed with which a computer can store or retrieve bits from its dynamic memory?

MOSFETs are poor conductors of electrical current hence it takes time to store or retrieve the charge that is in the memory capacitors.

Explanation:

Dynamic Random Access Memory (DRAM)  stores information bits in a memory cell. The cell is made up of a capacitor and a MOSFET transistor. The state of the capacitor can represented by the bits 1 and 0. 1 represents a fully charged capacitor while 0 represents its discharged state .Since MOSFETs are poor conductors of current it takes time  to charge the capacitor and also discharge it , this in turn limits the speed at which the computer can store and retrieve bits from its dynamic memory.

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