backup apps problem !!

[thepower]

hey all
i have iphone 3GS with IOS 4.1 my problem is when i try to transfer purchases from iphone with itunes i see warring and tell me no space delete some photos and videos i have very big space on my computer !! i don,t know itunes backup the apps to computer or itunes network !!??
small question .. if i update my IOS to 5.1.1 i lose my apps ??

 

[Weaselboy]

Not sure about the space warning, but upgrading from iOS 4 to iOS 5 will keep your apps.