Published by New Science Press, this text introduces general principles of protein structure, folding, and function, then goes beyond these basics to tackle the conceptual basis of inferring structure and function from genomic sequence. It is the first book in a series, Primers in Biology, employing a modular design in which chapters are divided into topics, each occupying one two-page spread that includes the relevant text, illustrations (in full color), definitions, and references. The book has five chapters. The first is an introduction to the principles of protein structure and folding, with emphasis on proteins' biophysical properties. The second describes the principles of the main biochemical functions of proteins, namely binding and catalysis, with a short section on the properties of structural proteins. Chapter 3 covers the regulation of protein function, containing concise descriptions of all the regulatory mechanisms that operate on proteins, from pH to phosphorylation, with several sections on protein switches based on nucleotide hydrolysis. Chapter 4 introduces the principles whereby structure and function are deduced from sequence, with illustrative examples. The final chapter addresses how data on protein structure is gathered, interpreted, and presented. Written for upper-level undergraduates and beginning graduate students, Protein Structure and Function will also be useful for working scientists needing an up-to-date introduction to the field.