To maintain the structure of the synapse, as with other synapses, there are many microtubules. The calyx has a large number of microtubules at the base of the terminal. These microtubules carry out a variety of functions, such as providing stability to the synapse, restricting the distribution of the synaptic vesicles, and localizing the mitochondria. Mitochondria have three important functions at the synaptic terminal: allowing the synapse to meet metabolic needs (especially for removal of calcium after depolarization), buffering the calcium by allowing uptake of calcium into the mitochondria, and providing energy for glutamate synthesis.