<?php $cat_name = uncategorized; //the certain category ID
$latest_cat_post = new WP_Query( array('posts_per_page' => 1, 'category__in' => array($cat_id)));
if( $latest_cat_post->have_posts() ) : while( $latest_cat_post->have_posts() ) : $latest_cat_post->the_post();  ?>

<h1><?php the_title(); ?></h1>	

<?php the_content(); ?>

<?php endwhile; endif; ?>