"Make straight the path..."

I find cyclical processes hard to understand. Maybe it's because I grew up in the age of digital clocks.

When I see a cycle, I like to draw it out as a linear sequence. For example, here is Figure 17.18, linearized to show the steps involved in adding one amino acid to a polypeptide chain. Comparing the top and bottom cartoons, you can see that the end is the same as the beginning. But shown this way, it is easier for me to think of a "beginning" and an "end." Click to enlarge...

By the way, happy new Year!