FoundationalConceptsNeuroscience

While not the most abundant neurotransmitters in the human brain,
these two molecules are perhaps the best known of the neurotrans-
mitters, due to their frequent mention in the news media. If you
were to randomly stop people on the street and ask them to name
a neurotransmitter, if they had any idea at all as to what you were
asking, they would likely answer with the name of one of these two
molecules.
Notice that within the diagrams for these molecules the benzene-
ring structure occurs. Also notice that each of these molecules con-
sists of a bunch of carbon atoms, several nitrogen and oxygen atoms,
and a bunch of hydrogen atoms around the periphery of the molecule,
all joined by chemical bonds so that a particular geometric shape
results. Thus, these molecules are appreciated to be just a bunch
of atoms (mostly carbon and hydrogen) connected together by the
sharing of electrons (covalent chemical bonds) to form a particular
geometric shape. It is their unique shapes that determine the proper-
ties of particular molecules within, say, the human nervous system.
If you spend time drawing a few molecular structures like those
of dopamine and serotonin, you very quickly appreciate that mostly
what you are doing is drawing lots of Cs (representing carbon atoms)
and Hs (representing hydrogen atoms). There may be a few other
atoms, like the several oxygen and nitrogen atoms in dopamine and
serotonin, but mostly there are Cs and Hs, lots and lots of Cs and Hs.
There can be so many Cs and Hs that it becomes difficult to notice
the most important things about the molecule, such as the overall
shape and what kinds of other atoms are part of the structure. Thus,
chemists have developed a shorthand language for depicting the
structures of organic molecules. In this shorthand language, the
structures of dopamine and serotonin look like this: