do I have to use the 4-pin power cable?

I am building a desktop computer for only the second time, and just discovered that the case's 4-pin power connector, coming up from the bottom, is simply not long enough to reach the socket near top left of the motherboard. Not even close. It's a full-sized roomy case and the board is considerably smaller.

Before I go spending a little money on an extension, I wonder if I have to plug in that cable anyway for the computer to run. I don't have the experience to know. I'm no gamer or any other sort of power user. I don't do much other than use office suite programs and the internet.