Workaround for: IF post IN category-id ?

I’ve made good use of the available conditional tags however haven’t found a way to create something like…

if (post-in-category-1) show { something-i-want-to-show-in-cat-1-posts-only } else { something-i-want-to-show-in-every-other-post }

I have two main parts to my blog: a main blog category which I will be adding information to that is available for comment from the general public, and the rest of my categories, which are state indexes, available to comment on only by registered members of that state.

I’m not an expert at coding but I think I have the jist of it! Any help is much appreciated!