It's everyone's favourite muscle group. The biceps (strictly, biceps brachii; you also have biceps on your legs) are funny muscles. They have two origins, giving them a long head and a short head up at the shoulder, and an insertion down onto the forearm. Specifically, the long head travels through a sheath in the front of the shoulder then attaches back into the glenoid tubercle, the short head attaches onto the coracoid process, and the distal end attaches onto the proximal end of the radius. Here are some pictures to point out where the thingamjigs attach to the doohickeys.
Now that I've turned you into a braindead mullet with that anatomy lesson, here are the implications for the above information:
1) The origins of biceps are on the scapulae, so, while they aren't very good at it, the biceps are involved in shoulder flexion.
2) The insertion is on the forearm bone that likes to rotate. Specifically, the biceps are an important muscle in supination.
When it comes to exercise, this tells us that when we do curls (for the gurls), a supinated grip will create a greater peak contraction than a neutral of pronated grip (these grips, in turn, cause other elbow flexors to get a good workout; this isn't a bad thing). Moving from neutral or even pronated throughout the ROM might (on paper) be even better, although that hasn't been my personal experience. Keeping the shoulders slightly flexed throughout the ROM will also allow a greater contraction.
This also means that, while pull ups and rows are great compound exercises that work the biceps, some form of isolation exercise would be good to polish things off, because pull ups use a pronated grip and move the shoulder into extension rather than maintaining flexion.
Use this information dump wisely. Goodnight.