A change to an environmental variable is only in effect in the current shell, i.e., the shell that is active when you type the command. An exported variable and an alias are only active in the current shell and all subshells (i.e., when you open a new terminal by loading your terminal emulator from the current terminal).
To have persistent variable definitions and alias definitions, valid as soon as you are logged in:
include the environmental variable definitions (e.g. PATH) in your ~/.profile file. That file is read when you log in and will be available to any application you launch, either from the menu or the terminal.
include alias definitions in your ~/.bashrc file. That file is read anytime you open an new interactive terminal and so will be available in any terminal (but not elsewhere).
Note: while your alias definitions also could be included in profile, it makes more sense to include them in ~/.bashrc so they only are defined in an interactive terminal and not elsewhere.