Find the chemicals
You get back to old thrash once more. Head for the security station and use the Save station and Store. Also be sure to use the Stasis recharger on your way to the objective.
Enter the room and use kinesis on the red barrel to take down the necromorph that attached itself to the wall. Enter the elevator to the right of the now-dead-monster and go up.
Slow down the moving platform and kill the necromorph. In order to get to the door visible in the second picture you will need to slow down the platform. Before you enter be sure to use the Save station.
Head for the chemistry lab, go down the elevator and when you get off be sure to pick up the Audio log. Go to the lab, take the Power node from the locker and check the two containers and a crate. On the table you will find a Force energy schematics. When you'll collect all the items approach the console and activate it. Few seconds later our chemicals are ready. After a shot cut-scene you will be forced to fight a new type of necromorphs that brakes out off the testing tube. Trying to take down it's limbs won't do much - it will regenerate them. Time to run. Go back the way you came to the laboratory.
Find the DNA sample
On your way to the security station you will be surprised by a large number of crawling necromorphs - line gun's alternative fire or flamethrower should help let you dispatch them quite easily. Save the game and resupply in the Store, then head to the Ishimura clinic.
After a short interactive cut-scene. The ER door will open and behind them you'll encounter another invincible monster. Shoot him in his groin to slow him down for a while.
It is not the end of your problems, however, as more necromorphs will appear and attack you, and you will have to survive until Kendra manages to open the door (the ones on the left side of the shining coil). It's your way out.
You're safe, at least for now. Proceed down the corridor until you reach a red can that can be lifted with kinesis and hurled at the monster you encountered before. If you time it right you can hurl it at its belly before it spawns the smaller necromorphs. After it's dealt with, go through the door to it's right.
Going forward you will reach the ER. Dr. Mercer's office is on the opposite side from the save point. Enter it, check the containers on the floor, collect the random items and an Audio log. Activate the console, take the container and get ready to fight for your life!