Biochemistry is really cool but, I just can't figure out how we know this stuff.

 

For example: Muscle physiology. How do we know the structures of the actin and miosin and how do we know about the calcium and entering and binding etc. It's not like you can just look at a muscle and see all of this. Is it jsut really good guesses or what?

 

This may be more of a biology question.

A lot of it is just progressively more sophisticated experiments, and poisons.

 

Figuring out that muscles cause movement is pretty easy; they bulge when we move, and injuries to them hamper movement. Dissection shows nerves going to them. We know from accidents with electricity that electricity causes muscles to contract/convulse. Given that and an appropriate model (usually a frog gastrocnemius), we can remove a muscle from a living organism, place it in a special solution to keep it alive (basically saltwater) and stimulate it to contract. By trying different levels and patterns of stimulation and measuring forces, we can determine things like muscles only exert tensile force when contracting. By selectively using poisons that do things like bind calcium or other elements, or block particular neurotransmitters, we can figure out what's involved. X-ray crystalography and other methods showed the structure of actin and myosin, and shortly thereafter, Andrew Huxley (grandson of the great Thomas Henry Huxley) proposed the sliding filament model.

 

The same can be seen in nerves or other tissues. Looking at the experiments in historical order can really help you see the chain of reasoning that lead to the current knowledge of a particular phenomenon or system, both in biology and other fields.

 

Mokele

One thing leads to another. Typically it's a conscious thought that creates a neurophysiological, biochemical reaction. Somewhere afterwards, tropomyosin is activated, and that eventually activated the actin within the muscle. After some other stuff, the muscles tighten.

 

Getting into the nitty gritty of that stuff can be difficult, and that's why a person has to develop spatial reasoning and a good imagination. Otherwise, it's a bunch of word memorization along with sequence memorization. I sometimes think to myself that the human brain is becoming like a computer when it thinks about how each action and reaction occurs in the body.

 

Given that and an appropriate model (usually a frog gastrocnemius), we can remove a muscle from a living organism, place it in a special solution to keep it alive (basically saltwater) and stimulate it to contract.

 

You mean galvanizing it, right?

I think it used to be called that; nowadays everyone just calls it 'stimulating', at least in the papers I've read.

 

Mokele