Current trends in pharmacology and physiology employ the idea that collective structural motions participate in protein folding and function, however there is considerable controversy as to whether these motions exist and if rather dynamics are entirely determined by driven Brownian motion. The role of large scale collective motions in protein picosecond dynamics is investigated through terahertz (THz) time domain spectroscopy and molecular dynamics simulations of cytochrome c as a function of oxidation and hydration. For both oxidation states the measured THz response rapidly increases with hydration up to ~.25 h, and then saturates above this level. A large increase in the picosecond response occurs with oxidation, with the largest flexibility increase for lowest hydrations and highest frequencies. Quasi-harmonic vibrational modes and dipole-dipole correlations are calculated from the molecular dynamics trajectories. The measured hydration dependence is reproduced by the vibrational density of states indicating collective motions contribute to the response. This is a direct demonstration of the existence of these collective motions. The large oxidation dependence is reproduced only by the dipole-dipole correlation function, indicating the contrast arises from side chain and bound water diffusive motions.