UGGG another deep HU situation that confuses me

[Go_Blue88]

Villian calls pf loosely...so I guess this turn could have helped him...but how...

Effective Stacks: 800.00

Hero raises to 12 with K[img]/images/graemlins/spade.gif[/img] K[img]/images/graemlins/club.gif[/img], Villian calls.

Flop-- Q[img]/images/graemlins/diamond.gif[/img] 2[img]/images/graemlins/club.gif[/img] 10[img]/images/graemlins/diamond.gif[/img]

Villian checks, Hero bets 16, Villian calls.

Turn-- 5[img]/images/graemlins/spade.gif[/img]

Villian checks, Hero bets 45, Villian raises to 175, Hero calls.

River-- 7[img]/images/graemlins/club.gif[/img]

Villian goes all-in for 496.00, Hero?

Ok so I don't think he has 55...and I'm 99% sure that he'd raise the flop if he hit big. So, either the 5 helped him or he's bluffing. I just don't get how the 5 could have helped him. Put him on Q5? 105? And if he had a hand like 10 5 or 2 5, would he play it so confidently this deep? Confusing hand for me.