A spark is what we would refer to as a heart. As long as a Transformer has a working spark, he will continue to function. However, if it would be damaged badly, its lights out for them. Sparks can be consumed, as shown by Megatron in Transformers The Movie video game for the DS. After killing Jazz, he is shown digging into the Autobot, and said he would enjoy feasting on his spark. Megatron also kills your Create-A-Bot, despite him saving Megs from his icy tomb, and eats your spark.