How to sleep

I am running Macbook pro with os x 10.4.11 & am wondering where the option to put the computer to sleep after shutting the lid is? Currently after I shut the lid it just dims the screen, signs out of wifi and runs idle but it is using a lot of battery life. What I want is for it to hibernate or sleep after I close the lid that way I can save on battery life when not plugged in. Is there an option for this?