I structure my workouts around major compound lifts - bench press, deadlifts, squats.
Very good advice for anyone looking at strength training. These are called compound lifts for a reason, they are not isolation exercises. They engage many secondary muscles in addition to working the primary muscles. Studies have also shown that these exercises help release chemicals and hormones that positively effect the recovery and building of all other muscles. So those squats are indirectly helping to produce better results in your bicep curls. I could go on, but just one more point of interest. Compound exercises also help to increase your post workout metabolic rate thereby helping to burn fat.
Not that you need it.