WHAT TO DO WITH THE RATKIN ACCESS CARD:
To the left of Commander Mako's office door, you will find an NPC that lets you repeat quests. Interact with said NPC, click 'yes' when she asks you if you would like to go on a mission.
Pick the 'Laboratory' mission and then click on 'PlagueSynth Storage'. It will be there if you have already done the mission. If not, then go finish Chapter 3.
Play the mission as normal, but at the end, do NOT approach the Ratkin lady. Hug the wall closest to the sparkling notes you will see on the top-left corner of your screen. If you have the card, there will be no blue wall, and you can pick up the notes.
You will get a pick-up order thingamajig for a lab suit. You have to go to the market to claim it. If you don't know where the market is, go to the elevator (assuming you have it fixed), leave the parking-lot and head to the nearest place with a door that opens. It's across the street from the parking-lot. You go in, talk to the lady behind the register, and you get the suit