hp z400 power button/led and hood sensor

hi there, i'm assembling a new pc using an hp z400 motherboard. some problems occours. 
1- the original power button cable ha a elettronic component  (feel like a diod) and i haven't because i don't have the cable because i've bought a new case wich have standard plug e play pin.is that component necessary to start the pc? 
2- searching and searching i saw thatthere is a hood sensor. is that sensor necessary to start the pc? how can i bypass thi sensor? (i'ts a normal switch, with two cable but at the motherboard i've 3 pins so i guess that the first and the third can be connected together to bypass an send a always closed signal to the pc