This chamber introduces the concept of pellets, pellet launchers and pellet receivers.
You must be careful around pellets though; as GLaDOS says, they're dangerous, and will instantly kill you if you touch them:
While safety is one of many Enrichment Center goals, the Aperture Science High-Energy Pellet, seen to the left of the chamber, can and has caused permanent disabilities, such as vaporization. Please be careful.
The objective here is to direct a pellet into the pellet receiver, which will then power the lift, enabling access to the chamberlock. Since there is a fixed orange portal end beneath the pellet launcher, it makes sense to put a portal above the pellet receiver, so that when pellets are launched, they go through the portal, and fly into the receiver. Notice that a red light is radiating out of the receiver, and this shows up on the ceiling directly above it. This can be used to accurately place a portal across from the pellet receiver. The pellet will fly through and be captured by the pellet receiver, which will then power the lift, allowing you to proceed to the next chamber.
No Cheating SpeedRun in One Segment for Mere Mortals
There's nothing that most people are able to do to bypass or finesse anything in this chamber. You can try placing the blue portal on the ceiling as close as possible to the platform and then dropping at an angle through the orange portal and directly onto the platform. There are YouTube videos that show this being done. If you can't manage this, just make sure not to waste any time. Use the glow from the pellet receiver to position the blue portal as you are moving forward. Go directly to the platform and wait until it comes down to chest height, then press up against it, jumping until you get up on it and it starts to go up again (without going all the way down). Press forward and jump again to get to the chamber lock without waiting for the platform to come all the way up. You should be in the exit chamberlock within fifteen seconds from when the entry chamberlock door opens.