Yes you do.
In 5e if you have the proficiency in something like acrobatics, you would add your dexterity modifier to the roll and your proficiency bonus. But if you didn't have proficiency in the acrobatics skill you would only add your dexterity modifier to it and not the proficiency bonus. This rule applies to saving throws as well.
Other things that can require proficiency
There are also other things other than ability checks that might require your proficiency bonus such as crafting something or trying to pick a lock. Crafting things or picking locks also fall under this rule of adding your proficiency bonus if you have proficiency in it. If you don't have proficiency in the picking locks or a crafting skill, such as metalworking or cooking, you just add your ability modifier to it.