IMac :: Would The DDR3 RAM Work

I have a Dec 08 purchased 3.06 Intel Core 2 Duo iMac with 4G of 800 MHz DDR 2 SDRAM installed and lovely it is too

I note the new iMac's now use DDR3 RAM and wonder (for future reference only) if the DDR3 RAM would work in my iMac if I swapped sticks.

I suppose whilst I'm on a roll of asking a question....I may as well try another one.....

Would (again for future reference) the ATI Radeon HD 4850 512MB be fitable (if that was a word....which it is not) in place of my GS 8800 512.