How to quickly startup/shutdown Oracle 11?
You can use the dbstart/dbshut scripts which come with an Oracle install. They are available under $ORACLE_HOME/bin.

After a fresh install you have to edit the /etc/oratab file:

# cat /etc/oratab
# format: $ORACLE_SID:$ORACLE_HOME:N|Y
my_sid:/home/juser/app/juser/product/11.2.0/dbhome_1:N
# sed -i 's/:N$/:Y/' /etc/oratab
# grep my_sid /etc/oratab
my_sid:/home/juser/app/juser/product/11.2.0/dbhome_1:Y


Then you can use the scripts like this:

$ whoami
juser
$ dbstart $ORACLE_HOME
$ # execute DB jobs ...
$ dbshut $ORACLE_HOME


dbstart brings all up which is needed for Pro*C/OCI programs.

Using dbstart/dbshut is an improvement above the custom method mentioned in the question:

method                time    called tools
―――――――――――――――――――――――――――――――――――――――――――――――――――――
dbstart              5.7 s    lsnrctl, sqlplus
dbshut               5.7 s    lsnrctl, sqlplus
custom startup      27.9 s    lsnrctl, sqlplus, emctl
custom shutdown     31.0 s    lsnrctl, sqlplus, emctl


(times on a Core i7/2.8GHz system, slow spinning hard disk.)

How dbstart/dbshut work

A dbstart $ORACLE_HOME$ call is basically equivalent to:

$ lsnrctl start
$ echo -e 'connect / as sysdba\nstartup\nquit'| sqlplus /nolog


And a dbshut $ORACLE_HOME$ is basically equivalent to:

$ lsnrctl stop
$ echo -e 'connect / as sysdba\nshutdown\nquit'| sqlplus /nolog


(you can verify if everything is shutdown via ps aux | grep 'tnsl\|ora')

Note that the order of the commands is important. That means when lsnrctl start is executed after the sqlplus-startup command then the Pro*C/OCI program still complains about an unavailable TNS-listener.

And this is exactly the problem with the command sequence in the question - where the emctl start just workarounds the wrong order because it fixes the TNS-listener setup part.

Also note that for executing Pro*C/OCI programs the EMCTL service is not needed.