Why are fibrous proteins more stable than globular proteins??Watch
They are also very resistant to pH change because they are mostly made of glycine (R group is H, the simplest amino acid) which has no proton accepting or donating groups, thus no hydrogens can be lost or gained onto the molecule to change its shape (except at the points where it is an amino acid other than glycine).
Globular proteins are made of many different amino acids, many of which are very sensitive to pH changes because they have complex R groups. They are also more sensitive to temperature changes because of their complex tertiary structure - means any rise or fall may cause the formation or the breakage of hydrogen/weak ionic bonds, changing the 3D shape and denaturing it.
Fibrous proteins have little or no tertiary structure meaning that they primarily have hydrogen bonding whereas globular proteins have tertiary structures so they have other types of bonding as well as hydrogen. Hydrogen bonding is very weak so why are fibrous proteins LESS sensitive to changes in temp and pH???