Query posts only if we’re in Category 2

I’m trying to make this line of code only query posts from Category 2 only if I’m at a single post from category 2. I’ve figured out how to make it display on any single post, but how can I restrict it to posts from category 2?

if (is_single()) :
query_posts('cat=2');
query_posts('posts_per_page=5');
load_template( TEMPLATEPATH . '/photos.php'); else : endif;