The hydrogen bond network in a 2-stranded, antiparallel ?-sheet. The side chains are sticking out above or below the plane of the picture. It less clear cut than in the case of the helix, in which direction to initially trace a beta sheet strand. The beta sheet can be infinitely extended due to the repeatable H-bonding pattern to either side of a strand.
Click this LINK to visit the original image and attribution information. Right click on the image to save the 800px teaching JPEG.
