I'm new to this community, so hopefully this is the right place to ask this question.
I know my question is really general, but in all of my biology courses we are merely taught the chemical pathways of common reactions in cellular metabolism, but we're rarely told how these reactions were determined or discovered. What approaches do molecular biologists take to determine what molecules are involved in what reactions, what order the reactions take place, where they take place, etc.? Some of these pathways involve tons of steps, huge molecules, and a bunch of enzymes and proteins, and I just don't see how anyone could have pieced it all together. For that matter, how is the molecular structure of anything in the cell determined? For example, what was the setup of the experiment that determined that TNF-R1 even existed on the surface of the cell membrane, and that it triggers the apoptosis pathway? Another example is photosynthesis -- I could see how maybe we could find PS1/2, cytochrome complexes, etc. in a soup of blended up cells, but how in the world did we figure out what each one does and in what order?
The average cell is just so tiny and complex that it doesn't seem like there's any feasible experimental design that could lead to the discovery of these things. Please enlighten me!