Over the summer I am thinking a bit about how proteins and other stuff move around inside our cells, and those of other living organisms. I am trying to do this quantitatively, and so I need numbers for various aspects of living cells and of organisms. So I was delighted to find that there is an entire searchable website just for numbers related to living organisms, called, sensibly enough, BioNumbers, plus a related book: Cell Biology by the Numbers, by Ron Milo and Rob Phillips. Both websites are a mine of useful information. For example, one entry is the total length of fibres of the protein collagen in our bodies. The total length is about 100 billion kilometres, or to put in another way, in each of our bodies there is enough collagen to go from the Earth to the Sun 10,000 times.
Collagen forms fibres (in the form of triple helices) that basically hold the cells of animals’ (including us) bodies into the tissues which make up the animal’s body. Gelatin is a form of treated collagen, that we are familiar with in the kitchen, as it is what holds jellies, panna cotta, etc together.
The BioNumbers website also informs me that the total mass of our species’ livestock (cows, sheep, pigs, etc) is comparable to the total mass of humans on the planet, i.e., about 1 billion tons of animal each, while that of every single wild mammal (lions, foxes, badgers, wildebeest, etc) combined, is a factor of ten lower.
This approximately 2 billion tons of humans, cows, sheep, etc together with the fact that collagen is the most abundant protein in the bodies of animals, may* mean that collagen is the most abundant protein on Earth. If so this will be our doing. It will owe its primacy to a combination of our impressive success in populating our planet, combined with our love of bacon, milk and beef.
* There is a very abundant protein plants use as part of photosynthesis, called rubisco, that is a rival for collagen, to be Most Abundant Protein on the Planet. Also, as both bacteria are so abundant, there may be competition both from an abundant bacterial protein such as a ribosomal protein, or an abundant invertebrate protein. We need more accurate data to decide definitively.