Find what is consuming more memory in linux

ps axu | awk '{print $2, $3, $4, $11}' | head -1 && ps axu | awk '{print $2, $3, $4, $11}' | sort -k3 -nr |head -5

The result is here

PID %CPU %MEM COMMAND
2222 3.2 3.8 /usr/lib/firefox/firefox
1937 0.2 1.5 /home/sorin/.dropbox-dist/dropbox
1073 3.8 1.0 /usr/bin/X
2407 0.2 0.9 pidgin
4105 1.5 0.8 /usr/lib/firefox/plugin-container

I see the 5 processes which consume most of the memory.
If I want to see the CPU, then I sort after second column => sort -k2

ps axu | awk '{print $2, $3, $4, $11}' | head -1 && ps axu | awk '{print $2, $3, $4, $11}' | sort -k2 -nr |head -5

outputs:

PID %CPU %MEM COMMAND
3448 16.9 0.2 rsync
1073 3.7 1.0 /usr/bin/X
2222 3.2 3.7 /usr/lib/firefox/firefox
830 2.5 0.5 /sbin/mount.ntfs
4105 1.4 0.6 /usr/lib/firefox/plugin-container