How do I display a specific function on a specific page

I have a website consisting of a 10-15 pages.
In one of my templates (lets call it Portfolio.php) I have an “includes” pointing to a php file where all of my hand coded functions reside.

On the same template (portfolio.php), I want to add certain functions from my “my_functions.php” file into that template, depending on what page is currently being displayed.

For example:

the template “portfolio.php” needs to be able to display 2 functions if its on page1, 2 different functions if its on page2, an 2 other functions if its on page3 (all of the functions are being included by an external “my_functions.php” file).

Im guessing all I have to do is:

if (  is_page('page1') ) {
function1();
function2();

} elseif ( is_page('page2') ) {
function3();
function4();
}

etc. etc.

Only problem is, I don’t know what the built in wordpress function of “pages” is. Is it “is_page_template”? I don’t think it is as each page is featuring the same template. So if I were to use “is_page_template” it would never display different functions because each page would have the same template.

Any suggestions?
I hope I explained myself well. If not let me know and i’ll try and word it differently to explain myself better. Thanks for any help.