The ratio of collagen in our tissues: https://www.peptan.com/collagen-in-our-bodies/

About the 3 dimensional structure of collagen: https://pdb101.rcsb.org/motm/4

The effects of age related collagen depletion: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1606623/

What role does collagen play in our body? https://www.healthline.com/nutrition/collagen