Can GPIO connectors be used for the same purposes as PIC i/o ports
Yes, a simple task like turning on a LED should be possible through the GPIO ports as well as the IO ports of a microcontroller. Sometimes there are restrictions on how easy it is to perform certain tasks through a GPIO instead of a IO of the microcontroller. The raspberry Pi for example has more difficulties implementing a PWM than a microcontroller, but it still should be possible. 

Simple answer: Yes you can practically almost use them for the same purpose.