Proteins in Action

So why are we going into all this tedious detail about how proteins function?

Because I want to explain how the genes control the information of the individual organisms and of the whole ecosystem. Maybe you only need to know that a gene can “turn on” and “turn them off,” and that’s how they control when and where the functions happen. Pigmentation happens only in pigment cells by producing the enzyme that causes pigment to form. Only in pigment cells. Or that most hormones influence cells, even though the hormone is outside the cell, because the cell has a protein on its cell surface that can respond to the hormone. Or that you can’t have the structures of your muscles (or their functions) unless the genes turn on (in muscle cells) that make the necessary proteins. Also none of these things can happen without organic energy that is available in the form of ATP that we have already discussed.

Protein functions depend upon their shapes. Every different kind of protein has a different shape.

Imagine here that the gray shape is a protein. Remember that “shape” means the physical distribution of the atoms and also the distribution of the energy. Physically the shape of the interacting molecules must fit together. In addition, energy interactions depend on the energy charges that are distributed over the surface of the molecule (or not). Positive charges attract negative charges. Similar charges repel each other. If there is no charge, the molecule usually is not inclined to interact.

Now imagine that the gray protein, on one of its sides, has an area that exactly attracts the black molecule. So whenever a black molecule is in the neighborhood it will pop right into the gray protein and stay there as long as conditions permit. And because the two molecules are attracted to each other, the energy relationships settle into a slightly new organization. As the energy relations over the protein readjust slightly to cuddle up to the black molecule, this causes all of the gray molecule to slightly shift. The shift moves charges and shapes all over the molecule until in this example the other side of the molecule is molded into a perfect “shape” to attract a third molecule. In the presence of ATP to provide the energy, these changes cause an important function to happen in the cell. And that function causes the gray protein to spit out both other molecules and return to normal. So it can do the same thing over again.

Or a receptor protein may be floating in the lipids of the membrane that surrounds the cell. The cell is maybe in an ovary and a hormone floats by. If the receptor is just the right shape to grab hold of the hormone, then the receptor-hormone complex will form and the receptor protein will be changed just enough that it activates something inside the cell.

In this way, and in other ways, the “shapes” of proteins are specific to their functions, and because they are specific they can be used to carry information from the gene to perform some action. Or proteins may be part of the structure of the cell. But to say again (and somewhat oversimplify), the point is that nothing happens unless the gene turns on to produce the protein and organic energy is available to activate the function of the protein.

The flow of information through the cell, the organism and the ecosystem is coded in the genes — the flow of energy discussed in chapter one is required for any work — the two paths cross to regulate almost everything that happens in life.

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