In this work, global hydration dynamics of solute molecules in water has been studied extensively by terahertz (THz) absorption spectroscopy. Hydration studies have been carried out in dynamical chemical equilibrium as well as in real-time while biochemical reactions proceeded. To characterize the role of water dynamics in a chemical reaction, a kinetic terahertz absorption (KITA) spectrometer has been developed, set up, and applied. In chemical equilibrium, model peptides based on the amino acids glycine, leucine, and tryptophan have been studied as well as native and denatured protein variants (ubiquitin) and functional enzymes (MT1-MMP). Furthermore, non-equilibrium dynamical properties of water network rearrangements has been observed by KITA spectroscopy in real-time for ubiquitin folding and for MT1-MMP-driven hydrolysis of peptide substrates. Comprehensive interpretation of the time-resolved KITA measurements has been achieved by merging KITA with state of the art real-time biophysical methods and simulations.