Fibril and hence the whole muscle. Elastin is a fibrous protein common in various soft tissues, like skin, blood vessels and lung tissue. Each monomer connects with each other, forming a 3D network, with ability to endure over 200% strain before deformation. Keratin is a structural protein mainly found in hair, nails, hooves, horns, quills. Basically keratin is formed by polypeptide chains, which coil into α-helices with sulfur cross-links or bond into β-sheets linked by hydrogen bonding. β-keratin, which is tougher than α-conformation, is more common in birds and reptiles. Resilin is an elastomeric insect protein, consisting of both α-helices and
Hair cell They have also improved frequency selectivity (frequency discrimination), which is of particular benefit for humans, because it enabled sophisticated speech and music. Outer hair cells are functional even after cellular stores of ATP are depleted. The effect of this system is to non-linearly amplify quiet sounds more than large ones so that a wide range of sound pressures can be reduced to a much smaller range of hair displacements. This property of amplification is called the cochlear amplifier. The molecular biology of hair cells has seen considerable progress in recent years, with the identification of the motor protein (prestin) that