Which directory should be writable to update wordpress?

I configured file permissions according to here like this.

apache user runs server and wordpress user owns directory, this user is only used for this site.

drwxr-xr-x  5 wordpress wordpress  4096 Apr 12 01:12 .
drwxr-xr-x 10 root      root       4096 Apr 10 16:19 ..
-rw-r--r--  1 wordpress wordpress   418 Sep 25  2013 index.php
-rw-r--r--  1 wordpress wordpress 19929 Jan 18  2013 license.txt
-rw-r--r--  1 wordpress wordpress  3193 Jan 27 20:18 readme-ja.html
-rw-r--r--  1 wordpress wordpress 10156 Jan 27 20:18 readme.html
-rw-r--r--  1 wordpress wordpress  4892 Oct  4  2013 wp-activate.php
drwxr-xr-x  9 wordpress wordpress  4096 Jan 27 20:18 wp-admin
-rw-r--r--  1 wordpress wordpress   271 Jan  9  2012 wp-blog-header.php
-rw-r--r--  1 wordpress wordpress  4795 Sep  6  2013 wp-comments-post.php
-rw-r--r--  1 wordpress wordpress  4255 Jan 27 20:18 wp-config-sample.php
-r--r-----  1 wordpress wordpress  4471 Apr 12 01:12 wp-config.php
drwxrws---  5 wordpress wordpress  4096 Apr 12 11:41 wp-content
-rw-r--r--  1 wordpress wordpress  2932 Sep 25  2013 wp-cron.php
drwxr-xr-x 12 wordpress wordpress  4096 Jan 27 20:18 wp-includes
-rw-r--r--  1 wordpress wordpress  2380 Oct 25 07:58 wp-links-opml.php
-rw-r--r--  1 wordpress wordpress  2359 Oct 25 07:58 wp-load.php
-rw-r--r--  1 wordpress wordpress 31909 Dec  4 05:12 wp-login.php
-rw-r--r--  1 wordpress wordpress  8235 Nov 13 20:58 wp-mail.php
-rw-r--r--  1 wordpress wordpress 10880 Nov  5 09:24 wp-settings.php
-rw-r--r--  1 wordpress wordpress 25665 Nov 13 12:23 wp-signup.php
-rw-r--r--  1 wordpress wordpress  4026 Oct 25 07:58 wp-trackback.php
-rw-r--r--  1 wordpress wordpress  3015 Oct 25 11:29 xmlrpc.php


$ ls -la wp-content/
total 24
drwxrws--- 5 wordpress wordpress 4096 Apr 12 11:41 .
drwxr-xr-x 5 wordpress wordpress 4096 Apr 12 01:12 ..
-rw-rw---- 1 wordpress wordpress   28 Jan  9  2012 index.php
drwxr-xr-x 3 wordpress wordpress 4096 Jan 27 20:18 languages
drwxr-x--- 4 wordpress wordpress 4096 Jan 27 20:18 plugins
drwxrws--- 5 wordpress wordpress 4096 Jan 27 20:18 themes

And add apache user to wordpress group

$ id apache
uid=48(apache) gid=48(apache) groups=48(apache),503(wordpress)

But with these permissions, I can't update wordpress itself or plugins. Which directory should be writable to update correctly and keep as possible as secure?