In Gnome you can create your own custom keyboard shortcuts to perform a variety of tasks. To create your own go to the menu bar and select System > Preferences > Keyboard Shortcuts. Once there, you'll have the Keyboard Shortcuts window open.

You'll see a list of tasks and their corresponding keyboard shortcuts - if the shortcut is Disabled, then this is not currently set up. You can create new shortcuts or edit existing shortcuts by clicking on the row and then press the key combination you want to use as a shortcut on the keyboard. Once you press this combination, it'll show up as the shortcut. To clear a shortcut, press the backspace key when the row is selected.