Final answer:
Exocytosis is the process in which membrane organelles fuse with the cell membrane to release their contents outside of the cell, such as the secretion of neurotransmitters at neuron synapses.
Step-by-step explanation:
The statement that best describes exocytosis is: B. Membrane organelles fuse with the membrane and release contents out of the cell. In biological processes, exocytosis is a way for a cell to expel material to the cell's exterior. This occurs when vesicles containing substances, like neurotransmitters or waste products, move to and fuse with the plasma membrane, thereby releasing their contents outside of the cell. An example of exocytosis is the secretion of neurotransmitters at synapses between the neurons, where the release of these chemical signals is essential for neural communication.
During an action potential, when the signal reaches the axon terminals of a neuron, calcium ions facilitate the fusion of vesicles to the presynaptic membrane, which allows neurotransmitters to be released into the synaptic cleft. These molecules can then bind to receptors on the postsynaptic membrane, passing along the signal to the next neuron.