Is there a way to customize the code which does the validation and saving of the profile ?

I have customized the edit profile code to show selective tabs as per the url parameter. For example for URL &task=account
The edit profile page shows the account information (change password fields).
If the url parameter is &task=preferences, the edit profile page only shows the user preferences tab.

But, the problem is, when the user tries to save the displayed tab, Joomla throws error (actually warning) for its core fields (firstname, lastname and email) being blank. Ofcourse, as the fields are not shown for editing, they are not sent to the profile saving code, so it takes them as blank. I need to customize this behavior for profile saving code.