penalty for not withholding enough tax

Help! I did not know (how would I know???) that I need to withhold on interest income??

There's a $380 penalty in my return! Shouldn't TurboTax have flagged the possible need to withhold quarterly? Is it true that there needs to be withholding on interest income and why? Anyway, I must please get the penalty removed or dramatically reduced. Would appreciate your help.