A new puzzle

A new puzzle, this one concerning the magic number seven (commented on from time to time, for example at references 1 and 2). With the number cropping up today in a very important bit of biological machinery, around since before the invention of animals and called the G protein-coupled receptor. This receptor being a long chemical which loops through the membrane of a cell seven times, with one loose end being outside and the other loose end being inside. A receptor which does something inside the cell when it is touched by a suitable chemical outside the cell, thus making a way for one cell to talk to another, possibly at some considerable distance. A receptor which is important in the human brain, doing something called neuromodulation.

I was pleased that seven had cropped up again, but sorry that I could find no explanation of why it should be seven loops that made the bit of machinery that was so ubiquitous and so important. There were, it seems, other bits of machinery along the same lines, but involving some smaller number of loops, but what is bought by this particular number remains beyond me.

I shall ask around.

Reference 1: https://psmv3.blogspot.com/2018/08/old-sevens.html.

Reference 2: http://psmv2.blogspot.com/2015/08/7-up.html.