This lecture covers an overview of post-translational modifications (PTMs) of proteins, focusing on phosphorylation, ubiquitination, and acylation. It discusses the structure and function of protein tyrosine phosphatases, the ubiquitin-proteasome system, and the reversible nature of ubiquitination. The lecture also delves into the mechanisms of serine/threonine phosphatases and the role of ubiquitin-like modifiers in cellular processes.