Welcome to Apple Support Communities.
I can't help directly with OS X 10.7 and Lightroom 5 requirements, but I can point you to specs for your mid-2007 MacBook 2,1: http://support.apple.com/kb/SP18
While it can HOLD two 2GB RAM modules for a total of 4GB RAM memory modules...
the design of the mid-2007 MacBook limits the system so can only address 3GB RAM. There is no way around this limitation.
The native LCD screen resolution is 1280x800. The Video RAM is fixed at 64MB. The video chipset is Intel GMA 950 There is no way to expand Video RAM or upgrade the chipset.
In my opinion, rather than spend much money to upgrade a 6-year-old mid-2007 MacBook, I'd invest the money toward a newer model used or refurbished MacBook or MacBook Pro with the ability to use at least 4GB RAM, a newer-generation processor, and a newer more capable video chipset.
For example, the 4-year-old base Mid-2009 Aluminum Unibody MacBook Pro 2.26Ghz offers better performance, holds up to 8GB RAM, an nVidia 9400M video chip with 256MB Video RAM, and runs cooler. My son just finished 4-years at college with his mid-2009, but he won't sell it to me and buy himself a new one---yet!
Mid-2009 MBP specs here: http://support.apple.com/kb/sp541
I'm still using my mid-2007 for many tasks, but high-end graphic-, video-, and photo-editing are not among them. (Yes, I'm saving up now to purchase a newer used/refurb MacBook capable of running OS X 10.8 Mountain Lion.)
Message was edited by: kostby