You'll notice that the bigger muscle groups can do more work.( Ex: you can leg press 2x + more than you can bench press.) I would do isolation exercises for your biceps to get stronger. Concentration curls and preacher curls are great examples of this as you're allowed very little body movement while doing the exercise, and that keeps you from "cheating".

Most guys think that doing curls makes your arms bigger. Wrong-o! Your triceps are devided into 2 muscle groups and they hide in the back of the arms. They're used to "push" instead of "pull". Ever seen the WWF wrestler Hulk Hogan? He's got HUGE triceps. I think he's referred to them as his "pythons".. lol.

Anyhow.. as with any exercise.. if you isolate, you'll get more out of the muscle you're picking on.

Good luck!