Keyboard shortuct on Mac

Keyboard shortuct on Mac

I am new to both Mac OSX and iPhone development. Coming from Windows and mostly use keyboard shortcuts to open windows/applications etc. As many of you know doing an alt + F opens the File menu [drop down], does there exists a similar keyboard shortuct so that we can make a drop down and then subsequently select a submenu using arrow keys. I am looking for a way as not each and every submenu does have a keyboard shortcut.